(artificial) neural network (ANN) Artificial neural networks are computational models that make predictions by simulating the functioning of human neurons.

abiotic Not associated with living organisms.abiotic transformation Process in which a substance in

the environment is modified by non-biological mech-anisms.

absorbed dose Amount of substance absorbed by an organism or organs and tissues of interest.

absorption Process of active or passive transport of a substance across biological membranes or other barriers into an organism. In the case of a mammal, this is usually through the lungs, gastrointestinal tract or skin. Absorption through the gills is an important transport route for many aquatic species.

abundance The degree of plentifulness.acceptable daily intake Estimated maximum amount of

an agent, expressed on a body mass basis, to which an individual in a (sub) population may be exposed daily over its lifetime without appreciable health risk. To calculate the daily intake per person, a standard body mass of 60 kg is used. The ADI is normally used for food additives, while the tolerable daily intake (TDI) is used for contaminants. See also reference dose, tolerable daily intake.

acceptable risk This is a risk management term. The acceptability of the risk depends on scientific data, social, economic and political factors, and on the perceived benefits arising from exposure to an agent.

acclimatization (1) Steady-state compensatory adjust-ments by an organism to the alteration of environ-mental conditions. Adjustments can be behavioural or physiological/biochemical. (2) An adaptation of organisms to some experimental conditions, includ-ing adverse stimuli. (3) Acclimation also refers to the time period prior to the initiation of a toxicity test in which aquatic organisms are maintained in untreated, toxicant-free dilution water with physical and chemi-cal characteristics (e.g., temperature, pH, hardness) similar to those to be used during the toxicity test.

accumulation Successive additions of a substance to a target organism, organ or environmental compart-ment, resulting in an increasing amount or concen-tration of the substance in the organism, organ or environment.

accuracy Reflects the agreement between the measured and the “true” value.

acid volatile sulphide (AVS) An extractable reactive pool of solid-phase sulphide that is associated with and available from the mineral surfaces of sediment to bind metals and may render that portion unavaila-ble and non-toxic to biota. Metals associated with the sulphide fraction of suspended matter and sediments in anaerobic environments include zinc, lead, copper, cobalt, nickel, cadmium, arsenic, antimony, mercury, manganese, and molybdenum.

actors in the supply chain In the context of REACH means all manufacturers and/or importers and/or downstream users in a supply chain.

acute Within a short period in relation to the lifespan of the organism, usually ≤ 4 d for fish and ≤ 14 d for rats. It can be used to define either the exposure or the response to an exposure (effect). An acute toxic effect would be induced and observable within a short peri-od of exposure. It can refer to an instantaneous expo-sure (oral gavage, injection, dermal application, etc.) or continuous exposures ranging from a few minutes to a few days.

acute tests Short-term tests (relative to generation time) usually at high concentrations.

acute toxicity The adverse effect occurring within a short time of exposure (relative to generation time). See also chronic and subchronic toxicity.

adaptation (1) Change in an organism, in response to changing conditions of the environment (specifical-ly chemical), which occurs without any irreversible disruption of the given biological system and with-out exceeding the normal (homeostatic) capacities of its response, and (2) a process by which an organism stabilizes its physiological condition after an environ-mental change.

added risk Difference between the incidence of an adverse effect in a treated group of organisms or a group of exposed humans and a control group (of the same organisms or the spontaneous incidence in humans).

additive effect An effect which is the result of chemi-cals acting together and which is the simple sum of the effects of the chemicals acting independently. See also antagonistic effect and synergism/potentiation.

additive toxicity The toxicity of a mixture of chemicals

GLOSSARY

C.J. VAN LEEUWEN

639

which is approximately equivalent to that expected from a simple summation of the known toxicities of the individual chemicals present in the mixture (i.e. algebraic summation of effects).

adenocarcinoma A malignant tumour originating in glandular tissue.

adenoma A tumour, usually benign, occurring in glan-dular tissue.

ADI See acceptable daily intake.adjuvant In immunology, a substance injected with anti-

gens (usually mixed with them but sometimes given prior to or following the antigen) which non-specifi-cally enhances or modifies the immune response to that antigen.

ad libitum feeding Providing continuous access to food.adsorption The adhesion of molecules to surfaces of sol-

ids.advection Physical transport or movement of a substance

with its medium (air, water, sediment).adverse effect Change in the morphology, physiology,

growth, development, reproduction or life span of an organism, system, or (sub) population that results in an impairment of functional capacity, an impairment of the capacity to compensate for additional stress, or an increase in susceptibility to other influences.

aerobic Requiring molecular oxygen.aerosol A compound dispersed as minute droplets or par-

ticles in a gas which allows widespread environmen-tal distribution, entry to the body via the respiratory tract, and widespread contamination of clothing, skin and eyes.

aetiology The study of the causes or origins of disease.AFNOR Association Francaise de Normalisation.AFNOR test Biodegradation test, which monitors the

reduction in DOC.age class A group of organisms of the same age within a

population.age composition The distribution of organisms among

the various age classes present in the population. The sum of the number of individuals in all age classes equals the population size.

age distribution The composition of a population in terms of how its abundance is distributed across age classes.

age-specific fecundity The pattern of fecundity of the various age classes.

age-specific mortality The pattern of survival rates of each age class.

Agency In the context of REACH means the European Chemicals Agency as established by this Regulation.

aggregation error The model error resulting from the

640 Glossary

use of a single set of parameters to represent a col-lection of distinct entities, such as individuals, in a population.

agonist A chemical with a positive action in the body.ALARA principle As Low As Reasonably Achievable.

This principle is a powerful regulatory tool in that risk managers are expected to do everything possi-ble to reduce risks to a limit which they can justify to their organization and to the regulatory authorities. See also precautionary principle (Chapter 1).

algicidal Lethal to algal population.algicide See pesticide.algistatic Inhibits algal population growth.alkalinity The acid-neutralizing (i.e. proton-accepting)

capacity of water; the quality and quantity of constit-uents in water which shift the pH towards the alkaline side of neutrality.

alkylating agent A substance which introduces an alkyl radical into a compound in place of a hydrogen atom.

allergy Symptoms or signs occurring in sensitized indi-viduals following exposure to a previously encoun-tered substance (allergen) which would otherwise not cause such symptoms or signs in non-sensitized individuals.

allometry The relationship between growth rates of dif-ferent parts of an organism or the study of the change in proportions with increase in size.

alloy means a metallic material, homogenous on a mac-roscopic scale, consisting of two or more elements so combined that they can not be readily separated by mechanical means.

ambient concentration The concentration of a chemical in a medium resulting from the addition of an incre-mental concentration to a background concentration.

ambient standard See environmental quality standard.anabolism Metabolic processes concerned with synthe-

sis.anadromy Fish born in freshwater, migrate to the sea for

growth and development but return to freshwater for reproduction. See catadromy.

anaerobic Not requiring molecular oxygen.analysis (1) Detailed examination of anything complex,

made in order to understand its nature or to determine its essential features, and (2) a formal, usually quanti-tative, determination of the effects of an action (as in risk analysis and impact analysis).

analysis of extrapolation error A method of risk analy-sis in which the probability density of an assessment endpoint, with respect to the concentration of a chem-ical (or other measure of exposure), is estimated by statistical extrapolation from toxicological data and

assessment endpoint Qualitative/quantitative expression of a specific factor with which a risk may be associat-ed as determined through an appropriate risk assess-ment.

assessment factor Numerical adjustment used to extrapolate from experimentally determined (dose-response) relationships to estimate the agent exposure below which an adverse effect is not likely to occur. See also safety factor and uncertainty factor.

ASTM American Society for Testing and Materials.asymptotic threshold concentration The concentration

of a chemical at which some percentage of a popu-lation of test organisms is in a state of approximate homeostasis for a prolonged period of time (not nec-essarily absolute). This can be demonstrated as the concentration at which the toxicity curve is approxi-mately asymptotic (parallel) to the time axis. The asymptotic LC50 is the concentration at which acute mortality has essentially ceased and will not change substantially with exposure time. That is, there is no evidence of significantly increasing effects due to a longer period of exposure.

atrophy Wasting away of the body, or an organ or tissue.aufwuchs Floral/faunal communities attached to sub-

merged surfaces.autopsy See necropsy.axenic Germ free. An axenic culture is a culture

containing only one type of micro-organism or one microbial species.

background concentration The concentration of a chemical in a medium prior to the action under consideration or the concentration that would have occurred in the absence of the prior action.

bactericide See pesticide.baseline toxicity The baseline toxicity is the toxicity cor-

responding to non-polar narcosis, so-called because no chemicals have been found to display lower toxic-ity than that due to non-polar narcosis. The baseline is often illustrated as a linear dependence of toxicity on the octanol-water partition coefficient (log Kow). It is normally assumed that baseline toxicity is the mini-mal (acute) toxic effect that a substance may produce, assuming complete solubility and no volatility.

base pairing The linking of complementary pairs of polynucleotide chains of nucleic acids by means of hydrogen bonds between opposite purine and pyrimidine pairs.

benchmark dose The statistical lower confidence limit of the dose corresponding to a small increase in effect over the background level. Typically, a 1% or 10% response level above the background is selected.

Glossary 641

the assessment endpoint.analysis of variance A method for testing the signifi-

cance of mean differences in which the total varia-tion in a set of scores is divided into separate parts; a parametric statistical procedure for evaluating the hypotheses about mean differences. In toxicology, a typical application of this method is to test for mean differences when comparing more than two experi-mental conditions.

aneuploidy Deviation from the normal number of chro-mosomes excluding exact multiples of the normal haploid complement.

ANOVA See analysis of variance.anoxia Strictly, the total absence of oxygen, but some-

times used to mean decreased oxygen supply in tis-sues.

antagonist A chemical which diminishes the effect of another chemical; the opposite of an agonist.

antagonistic effect The effect of a chemical in coun-teracting the effect of another; for example, a situa-tion where exposure to two chemicals together has less effect than the simple sum of their independent effects; such chemicals are antagonists.

anthropogenic Caused or influenced by human activi-ties.

antibody A protein that specifically recognizes and binds to an antigen.

antigen A substance that elicits a specific immune response when introduced into the tissues of an ani-mal.

APHA American Public Health Association.application factor (AF) A dimensionless value: the

chronically toxic threshold concentration of a chemi-cal divided by its acutely toxic concentration. The AF is usually reported as a range and is multiplied by the median lethal concentration of a chemical as deter-mined in a short-term (acute) toxicity test to estimate the expected no effect concentration under chronic exposure.

artefact Finding or product of an experimental or obser-vational technique that is not properly associated with the system under investigation.

article In the context of REACH means an object which during production is given a special shape, surface or design which determines its function to a greater degree than does its chemical composition.

artisol test Tests in which earthworms are exposed to chemicals in amorphous silicagel.

assessment Evaluation or appraisal of an analysis of facts and the inference of possible consequences con-cerning a particular object or process.

benefit A gain to a population, human health or a company. Expected benefit incorporates an estimate of the probability of achieving a gain.

benign Relating to a growth which does not invade sur-rounding tissue (nonmalignant).

benthic Living on the bottom of aquatic systems.bias An error caused by the systematic deviation of an

estimate from the true value.bioaccumulation The net result of multiple physiologi-

cal processes (ADME: Absorption, Distribution, Metabolism and Excretion) of a substance due to all routes of exposure.

bioaccumulation factor (BAF) A partition coefficient for the distribution of a chemical between an organ-ism exposed through all possible routes and an envi-ronmental compartment (air, water, soil or sediment) or food.

bioaccumulation factor, lipid based The quotient of the test chemical substance concentration in the lipid fraction of the test organism and the concentration of the truly dissolved compound in the test water, when the rate of uptake and clearance are equal.

bioactivation Biotransformation of a compound to a more toxic product.

bioassay Test used to evaluate the relative potency of a chemical by comparing its effect on a living organism with the effect of a standard preparation on the same type of organism. Bioassays are frequently used in the pharmaceutical industry to evaluate the potency of vitamins and drugs. Bioassay and toxicity test are not synonymous. See toxicity tests.

bioavailability The ability of a substance to interact with the biosystem of an organism. Systemic bioavailabil-ity will depend on the chemical or physical reactivity of the substance and its ability to be absorbed through the gastrointestinal tract, respiratory tract or skin. It may be locally bioavailable at all these sites.

biochemical mechanism A chemical reaction or series of reactions, usually enzyme catalyzed, which pro-duces a given physiological effect in a living organ-ism.

biochemical (or biological) oxygen demand (BOD) A measure of the rate at which molecular oxygen is con-sumed by microorganisms during oxidation or organ-ic matter. The standard test is the 5-day BOD test, in which the amount of dissolved oxygen required for oxidation over a 5-day period is measured. The results are measured in mg of oxygen/L (mg/L).

biocide Non-agricultural pesticides to control the sever-ity and incidence of pests or diseases. Examples are disinfectants and slimicides for the control of algal,

fungal or bacterial growth.biocommunity The biotic part of an ecosystem.bioconcentration The net result of the uptake, distri-

bution and elimination of a substance due to water-borne exposure of an organism.

bioconcentration factor (BCF) (1) The quotient of the test chemical substance concentration in the test organisms (Cf) and the concentration in the test water (Cw) at steady-state conditions, i.e. when the rate of uptake and clearance are equal, and (2) the ratio between the uptake rate constant (k1) and depuration constant (k2), assuming first-order kinetics.

bioconcentration factor, lipid based (BCF) The quo-tient of the test chemical substance concentration in the lipid fraction of the test organism and the concen-tration in the test water, when the rate of uptake and clearance are equal.

biodegradation Breakdown of a substance catalyzed by enzymes. See also primary biodegradation, ultimate aerobic biodegradation and mineralisation.

biokinetics See pharmacokineticsbiological half-life (t1/2) The time needed to reduce the

concentration of a test chemical in environmental compartments or organisms to half the initial concen-tration, by transport processes (e.g. diffusive elimina-tion), transformation processes (e.g. biodegradation or metabolism) or growth. t1/2 = ln2/k (for first-order kinetics).

biological monitoring Analysis of the amounts of poten-tially toxic substances or their metabolites present in body tissues and fluids as a means of assessing expo-sure to these substances and aiding timely action to prevent adverse effects. The term is also used to mean assessment of the biological status of populations and biocommunities at risk in order to protect them and to obtain an early warning of possible hazards to human or environmental health. Also called biomonitoring.

biomagnification Result of the processes of bioconcen-tration and bioaccumulation by which tissue concen-trations of bioaccumulated chemicals increase as the chemical passes up through two or more trophic lev-els. The term implies an efficient transfer of chemical from food to consumer, so that residue concentrations increase systematically from one trophic level to the next.

biomagnification factor (BMF) Quantitative measure of a chemical’s tendency to be taken up through the food. It is obtained in feeding experiments by divid-ing the concentration of a chemical substance in a living organism by the concentration of the chemical substance in its food at steady-state.

642 Glossary

biomarker The use of physiological, biochemical, and histological changes of exposure and/or effects of xenobiotics at the suborganismal and organismal level.

biomarker of effect A measurable biochemical, physi-ologic, behavioural, or other alteration in an organism that, depending on the magnitude, can be recognized as associated with an established or possible health impairment or disease.

biomarker of exposure The chemical or its metabolite or the product of an interaction between a chemical and some target molecule or cell that is measured in a compartment or in an organism.

biomarker of susceptibility An indicator of an inher-ent or acquired ability of an organism to respond to the challenge of exposure to a specific chemical sub-stance.

biomonitoring (or biological monitoring) Monitoring methods to better understand the complex relation-ships between external and internal exposure and, consequently, the potential adverse health and envi-ronmental effects. In ambient monitoring living organisms are used as “sensors” in water/sediment quality surveillance and compliance to detect changes in an effluent or water body and to indicate whether aquatic life may be endangered. In health monitor-ing it is a general term comprising the following subcategories: (a) biological monitoring - biomark-ers of exposure such as internal dose or body burden, (b) biochemical effect monitoring - biomarkers of effective dose (also tissue dose), (c) biological effect monitoring - biomarkers of effect, and (d) clinical parameters - biomarkers of disease.

biosphere The part of the earth’s surface which supports and is inhabited by living things.

biota-sediment accumulation factor (BSAF) A specific type and form of bioaccumulation factor that is the ratio of lipid-normalized tissue chemical residue to organic carbon-normalized sediment chemical con-centration. Note that various other terms for this are used in the literature, including accumulation factor (AF).

biotic indices Use of biota to indicate the quality of the surrounding environment.

biotransformation Enzyme-catalyzed conversion of one xenobiotic compound to another via phase-I and phase-II reactions.

bioturbation Mixing of sediment/soil, by biological action, e.g. burrowing.

blank Is used interchangeably with the term “control”.Blok test Also known as “repetitive die away test”. Is a

BOD assessment of biodegradation.BOD See biochemical oxygen demand.body burden Total amount of a chemical present in an

organism at a given time.boundary of exposure scenario Limitations of the

applicability of exposure scenario, e.g. substances within a range defined by their properties, maximum duration and frequency of activities, specified target groups, etc. See also exposure scenario.

broad exposure scenario An exposure scenario covering more than one activity, process, sector, or substance for which the same risk management measures are sufficient for ensuring adequate control of risks. See also exposure scenario.

broodstock Adult fish undergoing physiological changes to produce either eggs or sperm.

BSAF See biota-sediment accumulation factor.bw Abbreviation for body weight.calcinosis Any of various pathologic conditions charac-

terized by the deposition of calcium salts in tissues.cancer Disease which results from the development of

a malignant tumour and its spread into surrounding tissues. See tumour.

carcinogenesis The development of cancer. Any chemi-cal which can cause cancer is said to be carcinogen-ic.

carcinogenicity Capacity of chemical, physical or bio-logical agents to induce malignant neoplasms.

carrying capacity (K) The maximum number of organ-isms that can be supported by a given unit of habitat. Often calculated as the long-term average abundance.

catabolism Metabolic processes concerned with degra-dation.

catadromy Fish born at sea which migrate to freshwater for growth and development but return to the sea for reproduction. See anadromy.

catalase A haem-based enzyme which catalyses the decomposition of hydrogen peroxide into oxygen and water. It is found e.g. in peroxisomes in the liver.

CBA See cost-benefit analysis.CEC Commission of the European Communities; the

executive body of the European Communities.cell line A defined population of cells which has been

maintained in a culture for an extended period and which has usually undergone a spontaneous process of transformation conferring an unlimited culture lifespan on the cells.

CEN Comité Européen de Normalisation (European Standardization Committee).

CERCLA (US) Comprehensive Environmental Response, Compensation and Liability Act.

Glossary 643

chelation The trapping of a multivalent ionic species by ionic bonding to a larger water soluble molecule to make the ion inactive in the biological matrix and to aid excretion.

chemical oxygen demand (COD) When organic materi-als are not easily degraded by microorganisms, strong oxidizing agents (e.g., potassium permanganate) are used to enhance oxidation. COD is thus measured instead of BOD (see BOD). COD values will be larg-er than BOD values.

chemical safety assessment (CSA) According to REACH this is the tool used by industry to determine which risk management measures and operational conditions are adequate for protecting human health and the environment.

chemical safety report (CSR) According to REACH this is the tool used by industry to document that the risk management measures and the related opera-tional conditions are sufficient for protecting human health and the environment.

cholinesterase inhibitor A substance which inhibits the enzyme cholinesterase and thus prevents transmission of nerve impulses from one nerve cell to another, or to a muscle.

chromosomal aberration An abnormality in chromo-some number or structure.

chromosome The heredity-bearing gene carrier in the cell nucleus, composed of DNA and protein.

chronic Extended or longterm exposure to a stressor (conventionally taken to include at least a tenth of the lifespan of a species) or the effects resulting from such exposure. Long-term effects related to changes e.g. in metabolism, growth, reproduction, or ability to survive. Exposure concentrations are usually low. See also acute and subchronic toxicity.

chronic toxicity Chronic toxicity refers to the long-term adverse effects on an organism following constant dosing of a toxicant over a significant time period. The endpoint may be lethality, in which case, the dose or concentration causing a 50% effect (LD50 or LC50) may be determined. In addition to lethali-ty, additional information may be gained from a chronic toxicity study, for example organ toxicities and tumour formation. See also chronic value and NOEC.

chronic value The geometric mean of the NOEC and LOEC in tests with a chronic exposure.

clastogens Agents which cause chromosomes to break.clearance The process of losing a chemical substance

from a test organism. Also called depuration or elimi-nation.

clone A large number of cells or molecules genetically identical to a single ancestral cell or molecule.

CNS Central Nervous System.coefficient of variation (CV) The standard deviation of

a sample relative to the mean. It can be expressed as a fraction or as a percentage.

cohort A group of individuals, identified by a common characteristic, that are studied over a period of time.

cometabolism Process by which a normally non-biode-gradable substance is biodegraded only in the pres-ence of an additional carbon source.

community Collection of populations living together in same place and at same time which, therefore, may interact with one another. See ecosystem.

competent authority In the context of EC legislation it means the authority or authorities or bodies estab-lished by the Member States to carry out the obliga-tions arising from a Regulation or a Directive.

compliance In accordance with legislative or regulatory requirements.

concentration The quantifiable amount of a chemical in air, water, food, sediment, tissue, or any other medi-um.

concentration-effect relationship Relationship between the exposure, expressed in concentration, of a given organism, system or (sub) population to an agent in a specific pattern during a given time and the magni-tude of a continuously-graded effect to that organism, system or (sub) population. See also effect assess-ment, dose-response relationship.

conductivity A numerical expression of the ability of an aqueous solution to carry an electric current. This ability depends on the concentration of ions in solu-tion, their valence and mobility, and the temperature of the solution. Conductivity is normally reported in the SI unit millisiemens/metre, or as micromho/centi-metre (1 mS/m = 10 mmhos/cm).

confidential business information (CBI) Information that a manufacturer/importer or downstream user is not free to disclose, in order not to harm their com-petitive ability on the market.

congeners (1) Substances whose structure, function or origin are similar to others and may match the same structure-activity relationship (SAR), and (2) refers to species which belong to the same genus.

conjugate A water soluble derivative of a chemical formed by its combination with glucuronic acid, glu-tathione, sulphate, acetate, glycine, etc.

continuous effect A response that can be measured on a continuum from zero (or even a negative value) to positive values such as growth and reproduction. See

644 Glossary

Glossary 645

quantal effect.continuous flow Tests in which solutions in test vessels

are renewed continuously by the constant inflow of a fresh solution, or by a frequent intermittent inflow. See also flow-through.

control A treatment in a toxicity test that duplicates all the conditions of the exposure treatments but contains no test material. The control is used to determine the absence of toxicity under basic test conditions (e.g. health of test organisms, quality of dilution water).

control/dilution water The water used for diluting the test substance, or for the control test, or both.

control limit The limiting airborne concentration of potentially toxic substances which is judged to be “reasonably practicable” in the working environment and which must not normally be exceeded.

convection A type of fluid flow like advection but likely to occur in high-energy environments (e.g., streams) where sand ripples may be found and contaminated sediment are not likely to be deposited.

corrosion The process of contact damage due to a destructive agent in tissues.

cost-benefit analysis (CBA) The procedure for deter-mining whether the expected benefits of a proposed action outweigh the expected costs.

covalent binding An irreversible interaction between xenobiotics or their metabolites and macromolecules such as lipids, proteins, nucleic acids.

criterion The level of exposure (concentration and dura-tion) of a contaminant in a particular medium that is thought to result in an acceptably low level of effect on populations, communities, or use of the medium (e.g. water-quality criteria, air-quality criteria).

critical body residue (CBR) The whole-body concen-tration of a chemical that is associated with a given adverse biological response. This assumes organisms are a single compartment, rather than the multiple compartments that they actually are, but it has con-siderable utility as a first approximation of dose.

CSA See chemical safety assessment.CSR See chemical safety report.culture A stock of animals or plants raised under well-

defined and controlled conditions to produce healthy test organisms. As a verb, it means to carry out this procedure of raising organisms.

cytochrome P-450 A haemprotein involved in phase-I reactions of xenobiotics.

cytogenetics The branch of genetics that correlates the structure and number of chromosomes with heredity and variation.

cytoplasm Cell contents, in which the nucleus, endoplas-

mic reticulum, mitochondria and other organelles are found.

cytotoxic Causing disturbance to cellular structure or function, often leading to cell death.

damage A loss of inherent quality suffered by an entity. See also harm.

dechlorinated water Chlorinated water (usually munici-pal drinking water) that has been treated to remove chlorine and chlorinated compounds from solution.

degradation Chemicals that are released in the envi-ronment are subject to different (biotic and abi-otic) degradation processes: biodegradation by microorganisms, photolysis by light, hydrolysis by water, oxidation by different oxidants (for instance, in the atmosphere by hydroxyl and nitrate radicals or by ozone). These degradative processes are usually modelled in terms of the rate constants of the corre-sponding chemical reactions.

degradation rate constant A first order or pseudo first order kinetic constant, k (d-1), which indicates the rate of degradation processes. For a batch experiment K is estimated from the initial part of the degradation curve obtained after the end of the lag phase.

deionized water Water that has been purified to remove ions from solution by passing it through ion exchange resin columns or a reverse osmosis system.

delayed effects Effects or responses that occur some time after exposure. Carcinogenic effects of chemicals typ-ically have a long latency period; the occurrence of a tumour may take years after the initial exposure.

de minimis risk A risk that is too small to be of real con-cern to society (negligible risk). Risks below 10-5 or 10-6 are generally viewed as de minimis in the US.

demography The study of populations, especially their age structure and growth rates.

denitrification Reduction of nitrate to nitrite, nitrous oxide or dinitrogen (N2) catalyzed by facultative aer-obic bacteria under anaerobic conditions.

density dependence A change in the influence of any factor (a density-dependent factor) that influences population growth as population density changes.

deoxyribonucleic acid (DNA) The constituent of chro-mosomes which stores the hereditary information of an organism in the form of a sequence of nitrogenous bases. Much of this information relates to the synthe-sis of proteins.

depuration The loss of a substance from an organism due to elimination and degradation. The rate of depu-ration is expressed by its half-life or the time needed to eliminate 50% of the substance in a non-contami-nated medium. This term is often referred to as the

depuration time (DT50).derived characteristics Properties of a chemical that are

defined by, dependent upon, or are approximations of fundamental properties and the prevailing environ-mental conditions.

dermal corrosion Defined in OECD test guideline 404 as the production of irreversible damage to skin; namely, visible necrosis through the epidermis and into the dermis, following the application of a test substance for up to four hours. Corrosive reactions are typified by ulcers, bleeding, bloody scabs, and, by the end of observation at 14 days, by discolouration due to blanching of the skin, complete areas of alo-pecia, and scars.

dermal irritation. Defined in OECD test guideline 404 as the production of reversible damage of the skin following the application of a test substance for up to 4 hours.

detergent A cleaning or wetting agent which possesses both polar and non-polar terminals or surfaces allow-ing interaction with non-polar molecules making them miscible with a polar solvent.

determinants of exposure Main parameters required for estimating exposure of humans or the environment. Such parameters may pertain to the exposure scenario (process conditions), worker and consumer exposure conditions, environmental conditions or properties of substances and preparations. A list of “determinants of exposure” is used to systematically check the life-cycle of the chemical for relevant exposure and which information is needed to perform the exposure assessment.

deterministic analysis An analysis in which all popula-tion and environmental parameters are assumed to be constant and accurately specified.

deterministic model A mathematical model which is fully specified and does not include a stochastic com-ponent.

detoxification (1) A process which renders a toxic mol-ecule less toxic by biotransformation, removal, or the masking of active functional groups, and (2) the treat-ment of patients suffering from poisoning in order to reduce the probability or severity of harmful effects.

detritus Organic debris from decomposing plants and animals.

detrivorous Organisms living on detritus.diffuse source Emission sources which are not point

sources.diffusion (nonbiological) Nonadvective transport due to

migration and mixing of dissolved suspended solutes (including particulates) in natural waters in response

to concentration gradients. Diffusion can be at the molecular level, due to Brownian motion producing random movements of the solute molecules (molec-ular diffusion), or it can be movements of solutes (including particles) due to turbulent eddies, velocity shear, or bioturbation (turbulent diffusion). The two types of diffusion result in mixing and dispersal of dissolved and bound chemicals.

direct toxicity Toxicity that results from and is readily attributable to the toxic agents(s) acting more or less directly at the sites of toxic action in and/or on the exposed organisms that are exhibiting the adverse biological response in question.

disaster (1) An act of nature or an act of man which is or threatens to be of sufficient severity and magnitude to warrant emergency assistance, and (2) a disruption of the human environment which the affected communi-ty cannot absorb and manage with its own resources.

dissolved organic carbon (DOC) The fraction of the organic carbon pool that is dissolved in water and that passes trough a 0.45 µm glass fibre filter. DOC quantifies the chemically reactive fraction and is an accurate measure of the simple and complex organic molecules making up the dissolved organic load. The majority of the DOC is humic substances.

dissolved organic matter (DOM) It is analogous to DOC (see DOC), but it refers to the entire organic pool that is dissolved in water.

dispersant A chemical substance which reduces the sur-face tension between water and a hydrophobic sub-stance (e.g. oil), thereby facilitating the dispersal of the hydrophobic substance throughout the water as an emulsion.

distilled water Water that has been passed through a distillation apparatus to remove impurities.

distribution Dispersal of a xenobiotic and its derivatives throughout an organism or environmental matrix, including tissue binding and localization.

distributor In the context of REACH means any natu-ral or legal person established within the Community, including a retailer, who only stores and places on the market a substance, on its own or in a preparation, for third parties.

diversity index Measure of richness of biota (number of taxa) and, usually, the evenness of their distribution in communities.

DOC See dissolved organic carbon.DOM See dissolved organic matter.domain of applicability The applicability domain (AD)

of a (Q)SAR model is the response and chemical structure space in which the model makes predictions

646 Glossary

with a given reliability.dose Total amount of an agent administered to, taken up

or absorbed by an organism, system or (sub) popula-tion. See also external dose and internal dose.

dose-effect relationship Relationship between the total amount of an agent administered to, taken up or absorbed by an organism, system or (sub) population and the magnitude of a continuously-graded effect to that organism, system or (sub) population. See also effect assessment, dose-response relationship, con-centration-effect relationship.

dose-related effect Any effect to an organism, system or (sub) population as a result of the quantity of an agent administered to, taken up or absorbed by that organism, system or (sub) population.

dose-response Relationship between the amount of an agent administered to, taken up or absorbed by an organism, system or (sub) population and the change developed in that organism, system or (sub) popula-tion in reaction to the agent. See also dose-effect rela-tionship, dose-effect assessment, effect assessment, concentration-effect relationship.

dose-response assessment Analysis of the relationship between the total amount of an agent administered to, taken up or absorbed by an organism, system or (sub) population and the change developed in that organ-ism, system or (sub) population in reaction to that agent, and inferences derived from such an analysis with respect to the entire population. Dose-response assessment is the second of four steps in risk assess-ment. See also hazard characterization, dose-effects relationship, effect assessment, dose-response rela-tionship, concentration effect relationship.

dose-response curve Graphical presentation of a dose-response relationship.

dose-response relationship Relationship between the total amount of an agent administered to, taken up or absorbed by an organism, system or (sub) population and the changes developed in that organism, system or (sub) population in reaction to the agent. See also dose-effect relationship, effect assessment, concentra-tion effect relationship.

downstream user In the context of REACH means any natural or legal person established within the Community, other than the manufacturer or the importer, who uses a substance, either on its own or in a preparation, in the course of his industrial or pro-fessional activities. A distributor or a consumer is not a downstream user. A re-importer exempted pursuant to Article 2(4)(c) of REACH shall be regarded as a downstream user; EC European Communities.

ECETOC European Centre for Ecotoxicology and Toxicology of Chemicals.

ecosystem Collection of populations (microorganisms, plants and animals) that occur in the same place at the same time and can, therefore, potentially interact with each other as well as their physical and chemical environments and thus form a functional entity.

ecotoxicology The study of the toxic effects of chemical and physical agents in living organisms, especially on populations and communities within defined ecosys-tems; it includes the transfer pathways of these agents and their interaction with the environment.

ECx Effective concentration; the concentration which affects X% of a testpopulation after a specified expo-sure time. The EC50 usually relates to effects other than lethality (e.g. immobilization, growth rate, equi-librium, developmental abnormality or deformity) in 50% of the test organisms. The effect concentration may refer to other percentages such as 10%, 70%, e.g. EC10 and EC70 etc.

ED50 Dose that affects a designated criterion (e.g. behavioural trait) of 50% of the population observed. Also known as median effect concentration/dose. See also ECx, LC(D)50 and IC(D)50.

edaphic Pertaining to the soil.eddy diffusion Irregularity in the diffusion of solute

molecules which occurs in a porous chromatographic support. The phenomenon is due to the fact that (a) the pathlengths of some solute molecules are either shorter or longer than those of most of the molecules, and (b) the rate of solvent flow varies in different regions of the porous support.

EEC See estimated (or expected) environmental concen-tration.

effect Change in the state or dynamics of an organism, system or (sub) population caused by the exposure to an agent.

effect assessment Combination of analysis and inference of possible consequences of the exposure to a particu-lar agent based on knowledge of the dose-effect rela-tionship associated with that agent in a specific target organism, system or (sub) population.

effluent A complex waste material (e.g., liquid industrial discharge or sewage) that may be discharged into the environment.

EINECS European Inventory of Existing Commercial Chemical Substances: a list of all chemicals either separately or as components in preparations sup-plied to a person in an EC Member State at any time between 1 January 1971 and 18 September 1981.

electrophilicity Electrophilicity is the molecular or sub-

Glossary 647

structural property of having an attraction for elec-trons or negative charge. Molecular electrophilicity is often described by the molecular orbital properties the energy of the lowest unoccupied molecular orbital (ELUMO) and superdelocalisabilities.

elimination The combined process of metabolism and excretion which results in the removal of a compound from an organism.

elimination rate constant (ke) The first-order one-com-partment constant to describe the overall clearance of a chemical substance from an organism.

ELS Early Life Stage.elutriate An aqueous solution obtained after adding

water to a solid substance (e.g. sediment, tailings, drilling mud, or dredging spoil), shaking the mix-ture, then centrifuging or filtering it or decanting the supernatant.

embryo The undeveloped young animal, before it is born or hatches from the egg. See also foetus.

emission Release of a substance from a source, including discharges into the wider environment.

emission standard A quantitative limit on the emission or discharge of a potentially toxic substance from a particular source. The simplest example is a uniform emission standard where the same limit is placed on all emissions of a particular contaminant. See also limit value.

emulsifier A chemical substance that aids the fine mix-ing (in the form of small droplets) with water of an otherwise hydrophobic substance. See also disper-sant.

endocrine Pertaining to hormones or glands that secrete hormones directly into the blood stream.

endogenous Arising within or derived from the organ-ism.

endoplasmic reticulum A complex pattern of mem-branes that permeates the cytoplasmic matrix of cells and in which biotransformation reactions of the mono-oxygenase enzyme systems occur. May be iso-lated as microsomes following cell fractionation pro-cedures.

endpoint In toxicity testing and evaluation it is the adverse response in question that is measured. Endpoints vary with the level of biological organi-zation being examined but include changes in bio-chemical markers or enzyme activities, mortality or survival, growth, reproduction, primary production, and changes in structure (and abundance) and func-tion in a community. Endpoints are used in toxicity tests as criteria for effects.

endpoint assessment A quantitative or quantifiable

expression of the environmental value considered to be at risk in a risk analysis. Examples include a 25% or greater reduction in gamefish biomass or local extinction of an avian species.

enthalpy Heat content or the thermodynamic function H in H = E+PV, where E is the internal energy of the system, P is the pressure exerted on the system and V is the volume of the system.

entropy (1) A thermodynamic quantity that changes in a reversible process by an amount equal to the heat absorbed or emitted divided by the thermodynamic temperature, (2) function that is a measure of that part of the system that cannot perform useful work, and (3) the degree of randomness or disorder of a system.

environmental availability The portion of the total chemical material present in all or part of the environ-ment that is actually involved in particular processes and is subject to all physical, chemical, and biologi-cal modifying influences. It defines the total amount of material potentially available to organisms.

environmental bioavailability The ratio of the uptake clearance divided by the rate at which an organism encounters a given contaminant in a medium (e.g., water, food) being processed by the organism. This is a measure of an organism’s extraction efficiency, via respiratory, dietary, and surface absorption proc-esses, from the environmentally available portion of a material.

environmental compartments Subdivision of the envi-ronment which may be considered as separate boxes, and which are in contact with each other. A simple model would separate the environment into air, water, and soil, with biota, sediment (bottom and suspend-ed), layering of water bodies and many refinements being allowed if data to support their inclusion are available. See also Chapters 3 and 4.

environmental fate Destiny of a chemical or biological pollutant after release into the natural environment.

environmental impact assessment A type of assessment that attempts to reveal the consequences of proposed actions as an aid to decisionmaking.

environmental quality objective (EQO) The quality to be aimed for in a particular aspect of the environ-ment. For example, the quality of water in a river should be such that coarse fish can maintain healthy populations. See also quality objective.

environmental quality standard (EQS) The concentra-tion of a potentially toxic substance which is permit-ted in an environmental component, usually air (air quality standard) or water, over a defined period. Synonym: ambient standard. See also limit value.

648 Glossary

environmental risk analysis Determination of the prob-ability of adverse effects on humans and other biota resulting from an environmental hazard (a chemical, physical, or biological agent occurring in or mediated by the environment).

environmental transport The movement of contami-nants from their point of release through the vari-ous compartments to locations where exposure is assumed to occur.

enzyme A protein which acts as a highly selective cata-lyst permitting reactions to take place rapidly in liv-ing cells under certain physiological conditions.

enzyme induction De novo synthesis of an enzyme or activation of an existing enzyme.

enzyme inhibition A process leading to the reduced activity of an enzyme.

enzymic (or enzymatic) process A chemical reaction or series of reactions catalyzed by an enzyme or enzymes.

EPA Environmental Protection Agency.epibenthic Living on the bed of aquatic systems.epidemiology The study of the incidence, distribution

and causes of disease, or the statistical study of cat-egories of persons and the patterns of diseases from which they suffer in order to determine the events or circumstances causing these diseases.

epifauna Living on the surface of sediment in aquatic systems. See also infauna.

epigenetic changes Changes in an organism brought about by alterations in the action of genes. Epigenetic transformation refers to those processes which cause normal cells to become tumour cells without any mutations occurring. See also mutation, transforma-tion and tumour.

episodic Discontinuous effect, e.g. due to accidental spill or periodic stormwater discharges from sewers.

EPPO European and Mediterranean Plant Protection Organization.

equilibrium In a thermodynamic sense this indicates that both a steady state of flux and an equivalence in chemical activity have been reached in compart-ments or phases separated by a membrane or bound-ary across which the chemical fluxes occur. See also steady-state.

equilibrium partitioning (EqP) An approach for esti-mating the fate of chemicals (primarily organics) in the aquatic environment that is based on the assump-tion than a steady-state can be achieved, and usually is achieved, between the activity of chemicals (usu-ally approximated as concentration) in the various component phases-water, sediment, organisms. The

EqP approach is often exploited, for interpretation and extrapolation purposes, by normalizing chemi-cal concentrations based on the lipid content of the aquatic organisms and the organic carbon content of the sediments. These normalized BSAF values are considered to be independent of particular sediments and species.

ESIS European chemical Substances Information System.

estimated (or expected) environmental concentration (EEC) The concentration of a material estimated to be likely to occur in environmental waters to which aquatic organisms are exposed as a result of planned manufacture, use, and disposal.

ET50 The time it takes for a toxicant to affect 50% of a population with respect to a specific criterion.

EU European Union.eukaryote An organism (e.g. plant or animal) whose

cells contain a membrane-bound nucleus and other membranous organelles. See also prokaryote.

European Inventory of Existing Commercial Chemical Substances See EINECS.

EUSES European Union System for the Evaluation of Substances.

eutrophic Nutrient rich (aquatic) system with a high or excessive rate of biological production. See also oli-gotrophic.

eutrophication A complex series of interrelated changes in the chemical and biological status of a water body, most often manifested as a depletion of the oxygen content caused by the decay of organic matter result-ing from a high level of primary productivity and typ-ically caused by enhanced nutrient input.

excretion Removal of a substance or its metabolites from an organism by the discharge of biological mate-rial, including urine, faeces, expired air, mucus, milk, eggs, and perspiration.

existing chemicals Chemicals listed in the EINECS (EC legislation). See also EINECS.

exogenous Resulting from events or derived from mate-rials external to an organism. See also endogenous.

expected environmental concentration The calculated concentration of a chemical in a particular medium at a particular location at a particular time.

expert judgement Opinion of an authoritative person on a particular subject.

expert system Any formalised system, not necessar-ily computer-based, which enables a user to obtain rational predictions about the properties or activities of chemicals. All expert systems for the prediction of chemical properties or activities are built upon

Glossary 649

experimental data representing one or more effects of chemicals in biological systems (the database), and/or rules derived from such data (the rulebase).

exponential growth The growth of cells, organisms or populations in which the number/mass increases exponentially and growth at any time is proportional to the number/mass present.

exposure Concentration or amount of a particular agent that reaches a target organism, system or (sub) popu-lation in a specific frequency for a defined duration.

exposure assessment Evaluation of the exposure of an organism, system or (sub) population to an agent (and its derivates). Exposure assessment is the third step in the process of risk assessment. In the context of REACH two tiers can be distinguished: (a) Tier 1 exposure estimation. This is the first exposure esti-mation step leading to risk characterisation with the purpose of assessing whether risks are adequately controlled. In the first tier of the exposure estimation, simpler assessment steps, model interfaces and mod-els are used to identify potential risks. The main goal of a tier 1 model is to allow simplified (automated) use of models, thus increasing the efficiency of the risk assessment process. (b) Tier 2 exposure estima-tion. This is the second, more refined exposure esti-mation step leading to risk characterisation with the purpose of assessing whether risks are adequately controlled. Tier 2 exposure models may introduce additional model parameters, a more complicated interface or more complicated model.

exposure model A conceptual or mathematical represen-tation of the exposure process.

exposure pathway The course an agent takes from the source to the target.

exposure period The time of continuous contact between an agent and a target.

exposure route The way an agent enters a target after contact (e.g., by ingestion, inhalation, or dermal absorption).

exposure scenario (1) According to the definition of OECD and IPCS an exposure scenario is a set of con-ditions or assumptions about sources, exposure path-ways, amount or concentrations of agent(s) involved, and exposed organism, system or (sub)population (i.e. numbers, characteristics, habits) used to aid in the evaluation and quantification of exposure(s) in a given situation. (2) In the context of REACH expo-sure scenario means the set of conditions, including operational conditions and risk management meas-ures, that describe how the substance is manufactured or used during its life-cycle and how the manufactur-

er or importer controls, or recommends downstream users to control, exposures of humans and the envi-ronment. These exposure scenarios may cover one specific process or use or several processes or uses as appropriate. See also boundary of exposure scenario, broad exposure scenario, final exposure scenario and iteration.

external dose Amount of a chemical that is inhaled, ingested, or comes in dermal contact and is avail-able for systemic absorption. External dose is usu-ally expressed in units of mg of chemical per kg body weight per day (mg/kg/d) See also internal dose.

extinction probability The probability that a popula-tion will become extinct within a specified interval of time.

extrapolation An estimation of a numerical value of an empirical (measured) function at a point outside the range of data used to calibrate the function or the use of data derived from observations to estimate values for unobserved entities or conditions.

extrapolation factor A quantity used in effect and expo-sure assessments to adjust estimated exposures or concentrations/doses for uncertainties, to make cor-rections in the data, or to improve safety.

eye corrosion Defined in OECD test guideline 405 as the production of tissue damage in the eye, or serious physical decay of vision, following application of a test substance to the anterior surface of the eye, which is not fully reversible within 21 days of application.

eye irritation Defined in OECD test guideline 405 as the production of changes in the eye following appli-cation of a test substance to the anterior surface of the eye, which are fully reversible within 21 days of application.

FAO Food and Agriculture Organization (of the United Nations).

fate Pattern of distribution of an agent, its derivates or metabolites in an organism, system, compartment or (sub) population of concern as a result of transport, partitioning, transformation or degradation.

FDA (US) Food and Drug Administration.fecundity (1) Ability to produce offspring frequently and

in large numbers, and (2) in demography, the physi-ological ability to reproduce.

FIFRA (US) Federal Insecticide, Fungicide and Rodenticide Act.

final exposure scenario The final exposure scenario in the context of REACH is the outcome of the “tenta-tive” exposure scenario and the iterative exposure estimate and risk characterisation in the chemical safety assessment process. It specifies the operational

650 Glossary

conditions and risk management measures required for adequate control of risks.

first-order process A chemical process in which the rate of reaction is directly proportional to the amount of chemical present.

first-order reaction A chemical reaction in which the velocity of the reaction is proportional to the concen-tration of one reactant.

first-pass effect Biotransformation of a xenobiotic before it reaches the systemic circulation. The biotransfor-mation of an intestinally absorbed xenobiotic chemi-cal by the liver is referred to as a hepatic first-pass effect.

fitness When used in a Darwinian sense, refers to capac-ity to reproduce and survive.

flocculation The formation of a light, loose precipitate (i.e. a floc) from a solution.

flow-through Tests in which solutions in test vessels are renewed continuously by the constant inflow of a fresh solution, or by a frequent intermittent inflow. See also continuous flow.

foci A small group of cells occurring e.g. in the liver, which are distinguishable in appearance or histo-chemically from the surrounding tissue. They are indicative of a lesion in its early stage, which may lead to the formation of neoplastic nodules or hepato-cellular carcinomas.

foetus (fetus) The young of mammals when fully devel-oped in the womb. In human beings, this stage is reached after about three months of pregnancy. Prior to this, the developing mammal is in the embryo stage.

Freundlich adsorption isotherm An empirical equation that describes the adsorption of a contaminant to soil. The equation is as follows: x/m = KfCe

1/n, where x/m is the concentration of the contaminant in soil (mg/kg), Ce is the contaminant concentration in the aque-ous phase at equilibrium (mg/L), Kf is the equilibri-um constant (the Freundlich adsorption constant) and 1/n is the contaminant-specific exponent. See also Chapter 3.

fugacity (1) The tendency for a substance to trans-fer from one environmental medium to another. (2) Analogous to chemical potential as it pertains to the tendency of a chemical to escape from a phase (e.g. from water).

full study report In the context of REACH means a complete and comprehensive description of the activ-ity performed to generate the information. This cov-ers the complete scientific paper as published in the literature describing the study performed or the full

report prepared by the test house describing the study performed.

functional group Organic compounds can be thought of as consisting of a relatively unreactive backbone and one or more functional groups. The functional group is an atom, or a group of atoms, which has similar chemical properties whenever it occurs in different compounds. It defines the characteristic physical and chemical properties of families of organic com-pounds.

fungicide See pesticide.gametes The eggs or sperm obtained from mature adult

animals.gastrointestinal Pertaining to or communicating with the

stomach and intestine.GEMs Genetically Engineered Microorganisms.gene A part of the DNA molecule which directs the syn-

thesis of a specific polypeptide chain.generation time The average length of time between the

birth of parents and the birth of offspring.genetic toxicology The study of chemicals which can

produce harmful hereditary changes in the genetic information carried by living organisms, in the form of deoxyribonucleic acid (DNA).

genome Chromosomal DNA information.genomics Techniques available to identify the DNA

sequence of the genome.genotoxicity Ability to cause damage to genetic mate-

rial or an adverse effect in the genome, e.g. mutation, chromosomal damage, etc. that may lead to a cancer. See also carcinogenicity and mutagenicity.

genotype The genetic constitution of an organism. See also phenotype.

Gibbs free energy That component of the total energy of a system that can do work under conditions of con-stant temperature and pressure. The Gibbs free ener-gy (G) is expressed by the thermodynamic function G = H-TS, where H is the enthalpy, T is the absolute temperature and S is the entropy.

good laboratory practice (GLP) Fundamental rules incorporated in national regulations concerned with the process of effective organization and the condi-tions under which laboratory studies are properly planned, performed, monitored, recorded and report-ed.

growth An increase in size or weight as a result of prolif-eration of new tissues.

guidance value Value, such as concentration in air or water, which is derived after allocation of the refer-ence dose among the different possible media (routes) of exposure. The aim of the guidance is to provide

Glossary 651

quantitative information from risk assessment to risk managers to enable them to make decision. See also reference dose.

half-life The half-life (commonly denoted as t1/2) is the time interval that corresponds to a concentra-tion decrease by a factor 2. Environmental half-life data generally reflect the rate of disappearance of a chemical from a medium, without identifying the mechanism of chemical loss. For example, loss of water may be due to a combination of evaporation, biodegradation and photolysis. If the elimination rate involves transport and transformation processes that follow first-order kinetics, the half-life time (d) and elimination rate constant k (d-1) are related by the equation t1/2 = -ln 2/k = 0.693/k.

Hansch analysis Hansch analysis is the investigation of the quantitative relationship between the biological activity of a series of compounds and their physico-chemical substituent or global parameters represent-ing hydrophobic, electronic, steric, and other effects, using a multiple regression method.

haploid The condition in which a cell con-tains only one set of chromosomes.

hardness The concentration of all cations in water that will react with a sodium soap to precipitate an insolu-ble residue. In general, hardness is a measure of the concentration of calcium and magnesium ions in water and is frequently expressed as mg/L calcium carbonate or equivalent.

harm (1) A loss to a species or individual as a result of damage. (2) A function of the concentration to which an organism is exposed and the time of exposure.

hazard Inherent property of an agent or situation having the potential to cause adverse effects when an organ-ism, system or (sub) population is exposed to that agent. See also risk.

hazard assessment A process designed to determine the possible adverse effects of an agent or situation to which an organism, system or (sub) population could be exposed. The process includes hazard identifica-tion and hazard characterization. The process focuses on the hazard in contrast to risk assessment where exposure assessment is a distinct additional step.

hazard characterization The qualitatitive and, wher-ever possible, quantitative description of the inherent properties of an agent or situation having the potential to cause adverse effects. This should, where possible, include a dose-response assessment and its attendant uncertainties. Hazard characterization is the second stage in the process of hazard assessment, and the second step in risk assessment. See also dose-effect

relationship, effect assessment, dose-response rela-tionship, concentration–effect relationship.

hazard identification The identification of the type and nature of adverse effects that an agent has as inher-ent capacity to cause in an organism, system or (sub) population. Hazard identification is the first stage in hazard assessment and the first in the process of risk assessment.

hazard quotient The PEC/PNEC ratio, i.e. the definition of environmental and/or health risks by combining the results of the exposure assessment (PECs) with the results of the effect assessment (PNECs or NOAEL). Although there is a clear difference between hazard and risk, hazard and risk quotients are often used syn-onymously.

HCp (HC5) Hazardous concentration for p% (5%) of the species, derived by means of a statistical extrapola-tion procedure. See Chapter 7.

Henry’s law constant The Henry’s law constant (H) is an air-water partition coefficient that expresses the tendency of a chemical to volatilise from an aqueous medium. It can be determined by measurement of the solute concentrations in both phases. Due to the difficulty of accurate analytical determination, the H constant is mainly calculated as the ratio of vapour pressure to solubility. See also Chapters 3 and 9.

Henry’s law Inchemistry. Henry’s law is one of the gaslaws, formulated by William Henry. It states that: at a constant temperature, the amount of a given gas dissolved in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid.

hepatocytes Liver cells.hepatotoxicity Toxicity to the liver.herbicides See pesticides.histology The study of the anatomy of tissues and their

cellular structure.histopathology The study of adverse changes in the

structure of tissues, usually using a microscope.humic acid Humic substance that is insoluble at acidic

pHs.homeostasis The tendency of an organism to maintain

physiological and psychological stability.hormesis An improvement in the state or performance of

an organism in response to low levels of exposure to a chemical that is toxic at higher exposure levels and is not a nutrient.

HPVC High Production Volume Chemical. See also EINECS and Chapters 12, 13 and 16.

hybridisation Formation of a double strand from two different, more or less complementary single nucleic

652 Glossary

Glossary 653

acid strands.Hydra Genus of small freshwater hydrozoan coelenter-

ates. It is a ubiquitous genus with few species.hydrophilic Describes the character of a molecule or

atomic group which has an affinity for water.hydrophilicity Hydrophilicity refers to the affinity of

a molecule or substitutent for a polar solvent (espe-cially water) or for polar groups. It represents the ten-dency of a molecule to be solvated by water.

hydrophobic Describes the character of a molecule or atomic group which has a tendency to repel water.

hydrophobicity Hydrophobicity refers to the associa-tion of non-polar groups or molecules in an aque-ous environment, which arises from the tendency of water to exclude non-polar molecules. It is related to lipophilicity. It represents the tendency of a molecule to partition between a polar and a non-polar phase, and is therefore often measured by a partition coef-ficient between a polar and non-polar phase (usually, but not always, octanol and water).It is often highly related to biological activity due to its strong relation-ship with the transport and distribution of a molecule, particularly through phospholipid membranes.

hydrosphere Water above, on or in the earth’s crust, including oceans, seas, lakes, groundwater and atmos-pheric moisture.

hyper Prefix meaning above or excessive.hypoxic (1) Abnormally low in oxygen content or ten-

sion, or (2) deficiency of oxygen.IC(D)50 Concentration that induces a 50% inhibition of

a designated process in an exposed population. Also known as median inhibitory concentration/dose. See also EC(D)50 and LC(D)50.

ICp The inhibiting concentration to produce a (specified) percentage effect. It represents a point estimate of the concentration of test substance that causes a desig-nated percent impairment in a quantitative biological function such as growth, reproduction or respiration. For example, an IC25 could be the concentration esti-mated to cause a 25% reduction in growth of fish, relative to the control.

identified use In the context of REACH means a use of a substance on its own or in a preparation, or a use of a preparation, that is intended by an actor in the supply chain, including his own use, or that is made known to him in writing by an immediate downstream user.

idiosyncrasy Specific (and usually unexplained) reaction of an individual to e.g. a chemical exposure to which most other individuals do not react at all. Example: some people react to their very first aspirin with a potentially fatal shock. General allergic reactions do

not fall into this category.immune response Selective reaction by the body to sub-

stances that are foreign to it or that the immune sys-tem identifies as foreign, as shown by the production of antibodies and antibody-bearing cells or by a cell-mediated hypersensitivity reaction.

immunotoxic Poisonous to the immune system.immunotoxicology The science that deals with the

immunotoxic effects of chemicals.impermeable The extent to which the membrane, skin or

exoskeleton prevents the passage of molecules (e.g., water, ions, proteins, fats or toxicants).

import In the context of REACH means the physi-cal introduction into the customs territory of the Community.

importer In the context of REACH means any natural or legal person established within the Community who is responsible for import.

incipient LC50 The concentration of a chemical which is lethal to 50% of the test organisms as a result of exposure for periods long enough for acute lethal action to cease. The asymptote (part of the toxicity curve parallel to the time axis) of the toxicity curve approximately indicates the value of the incipient LC50.

incremental unit risk estimate For an air pollutant, this is the additional lifetime cancer risk occurring in a hypothetical population in which all individuals are exposed continuously from birth throughout their lifetimes to a concentration of 1 μg/m3 of the pollut-ant in the air they breathe.

indicator A characteristic of the environment, e.g. a species, that provides evidence of the occurrence or magnitude of exposure or effects. Formal expressions of the results of measuring an indicator are referred to as measurement endpoints. Abundance, yield, and age/weight ratios are indicators of population pro-duction. A low cholinesterase level is an indicator of exposure to cholinesterase-inhibiting pesticides.

indicator species A species that is surveyed or sam-pled for analysis because it is believed to represent the biotic community, some functional or taxonom-ic group, or some population that cannot be readily sampled or surveyed.

indirect toxicity Adverse effects or toxicity that results from the agent(s) acting on and producing changes in the chemical, physical, and/or biological environment external to the organisms under study (e.g., decrease in food for predatory species due to direct toxicity from a chemical to prey may produce adverse effects in the predator species due to starvation rather than

inducing any direct chemical toxicity in predator organisms).

individual risk Probability that an individual person will experience an adverse effect.

induction Increase in the rate of synthesis of an enzyme in response to the action of an inducer (substance that causes induction) or environmental conditions, often the substrate of the induced enzyme or a structurally similar substance that is not metabolized.

infauna Lives in the sediment of aquatic systems. See also epifauna.

inhibition concentration (IC) A point estimate of the chemical concentration that would cause a given per-cent reduction (e.g., IC25) in a nonlethal biological measurement of the test organisms, such as reproduc-tion or growth.

initiating event The specific action that results in a risk being incurred.

initiation The ability of an agent to induce a change in tissue which leads to the induction of tumours after a second agent, called a promotor, is repeatedly admin-istered to the tissue. See also promotor.

initiator An agent which starts the process of tumour development, usually by acting on the genetic mate-rial.

insecticides See pesticides.interindividual variability Biological variation between

people.intake The process by which an agent crosses an outer

exposure surface of a target without passing an absorption barrier, i.e. through ingestion or inhala-tion. See dose.

intermediate In the context of REACH means a sub-stance that is manufactured for and consumed in or used for chemical processing in order to be trans-formed into another substance (hereinafter referred to as “synthesis”). REACH distinguishes 3 types of intermediates: 1. Non-isolated intermediate means an intermediate that during synthesis is not inten-tionally removed (except for sampling) from the equipment in which the synthesis takes place. Such equipment includes the reaction vessel, its ancil-lary equipment, and any equipment through which the substance(s) pass(es) during a continuous flow or batch process as well as the pipework for transfer from one vessel to another for the purpose of the next reaction step, but it excludes tanks or other vessels in which the substance(s) are stored after the manu-facture. 2. On-site isolated intermediate means an intermediate not meeting the criteria of a non-isolated intermediate and where the manufacture of the inter-

mediate and the synthesis of (an)other substance(s) from that intermediate take place on the same site, operated by one more legal entities. 3. Transported isolated intermediate means an intermediate not meeting the criteria of a non-isolated intermediate and transported between or supplied to other sites.

internal dose In exposure assessment, the amount of a substance penetrating the absorption barriers (e.g. skin, lung tissue, gastrointestinal tract) of an organ-ism through either physical or biological processes. See also external dose.

interstitial water The water in sediment or soil that sur-rounds the solid particles. The amount of interstitial water is calculated and expressed as the percentage ratio of the weight of water in the sediment to the weight of the wet sediment.

intra-individual variability Biological variation within people.

in vitro In glass, referring to studies in the laboratory usually involving isolated organs, tissues, cells or biochemical systems.

in vivo Within the living organism.IPCS International Programme on Chemical Safety.IRPTC International Register of Potentially Toxic

Chemicals.ischaemia Local deficiency in the blood supply and

hence oxygen to an organ or tissue due to constriction or obstruction of the blood vessels.

ISO International Organization for Standardization.IT50 Time required for a toxicant to inhibit a specified

process in 50% of the observed population. Also known as median inhibitory time. See also ET50 and LT50.

iteration In the context of risk assessment it is a cycle in the exposure assessment to change assessment ele-ments: hazard information, risk management meas-ures, defaults of the exposure assessment, conditions of use, etc. As a result, the exposure scenario can be adapted to reflect the additional information and insight gained. See also exposure scenario.

i.v. Abbreviation for intravenous (administration).joint action Two or more chemicals exerting their effects

simultaneously.karyotoxicity Disruption of chromosomal structure.knockout animals Genetically engineered animals in

which one or more genes, usually present and active in the normal animal, are absent or inactive.

lag phase The time from the start of a test until adap-tation of the degrading micro-organisms is achieved and the biodegradation degree of a chemical sub-stance or organic matter has increased to a detectable

654 Glossary

level (e.g. 10% of the maximum theoretical biodeg-radation, or lower, dependent on the accuracy of the measuring technique).

Langmuir adsorption isotherm An equation that describes the adsorption of a gas onto a solid which takes the same mathematical form as the Michaelis-Menten equation.

larva A recently hatched fish or other organism that has different physical characteristics than those seen in the adult.

LC(D)50 The median lethal concentration/dose (i.e., the concentration/dose of substance that is estimated to be lethal to 50% of the test organisms). The LC50 and its 95% confidence limits are usually derived by statistical analysis of mortalities in several test con-centrations, following a fixed period of exposure. The duration of exposure must be specified (e.g. 96-h LC50). See also median lethal concentration/dose.

LDn The dose of a toxicant lethal to n% of a test popula-tion.

leachate Water or wastewater that has percolated through a column of soil or solid waste in the environment.

lentic Non-flowing or still water; e.g. lakes, ponds.lesion A pathological disturbance such as an injury,

infection or a tumour.lethal Causing death by direct action. Death of fish is

often defined as the cessation of all visible signs of movement or other activity.

lethal body burden (LBB) The body residue of chemi-cal that is associated with mortality in short-term exposures.

life-cycle Series of stages, from a given point in one generation to same point in next generation, e.g. egg-larva-adult-egg (hyphenated when used as an adjec-tive, e.g. life-cycle strategy). See also life-cycle study and life history.

life-cycle study A chronic (or full chronic) study in which all the significant life stages of an organism are exposed to a test material. Generally, a life-cycle test involves the entire reproductive cycle of the organ-ism.

life history Sometimes considered synonymous with life cycle, but some see it as segment of life cycle, e.g. egg to adult not egg to egg (hyphen used in the same way as with life cycle).

ligand A small organic molecule bound to a macromol-ecule in a stable, but not covalent, bond. It is used in toxicology, particularly to describe molecules being transported by blood proteins or molecules binding to the haem iron of haem proteins. The nature of ligand binding and the strength of the bonds involved are

important.limit test (screening) A test in which organisms are

exposed to a maximal agreed upon substance concen-tration and a control to determine the potential toxic-ity of a toxicant.

limit value The limit at or below which Member States of the European Communities must set their envi-ronmental quality standards and emission standards. These limits are set by Community Directives.

linear free energy relationship (LFER) An LFER is an empirical relationship in which numerical parameters are associated with small perturbations in a parent molecule and are subsequently correlated with the change in the free energy of a certain reaction of the parent molecule versus the perturbed molecules. A classical example is the well-known Hammett equa-tion, in which sigma values are constructed for spe-cific substituents on a benzoic acid parent molecule. The linear correlation is then between the (summed) sigma values for a set of compounds and the pKa (free energy of acid dissociation) of those compounds.

lipophilic (1) Having an affinity for fat and high lipid solubility, and (2) a physicochemical property which describes a partitioning equilibrium of solute mol-ecules between water and an immiscible organic solvent, which favours the latter. Correlates with bio-accumulation.

lipophilicity Lipophilicity refers to the affinity of a mol-ecule or of a substituent for a lipophilic environment.

liver nodule A small node, or aggregation of cells in the liver.

loading Ratio of animal bio-mass to the volume of test solution in an exposure chamber.

LOEC(L) Lowest Observed Effect Concentration (Level). The lowest concentration of a material used in a toxicity test that has a statistically signifi-cant adverse effect on the exposed population of test organisms compared with the controls. When derived from a life cycle or partial life-cycle test, it is numeri-cally the same as the upper limit of the MATC. The LOEC is generally reserved for sublethal effects but can also be used for mortality, which might some-times be the most sensitive effect observed. See also NOEC.

logistic curve A function, often applied to growth curves, fitting the general equation: y = k/(1 + ea+bt), where t represents time, y the bw or population size and b is greater than 0. In the logistic equation the percentage rate of increase decreases linearly as size increases. The resulting curve continually rises, slowly at first, more rapidly in the middle phase and slowly again

Glossary 655

near the end of growth. See also Chapter 7.logit transformation A transformation that relates the

response to a given concentration or dose of a toxi-cant to the response in the absence of the toxicant, using the following formula: logit = log [B/(Bo-B)] where B is the toxicant and Bo the response in the absence of toxicant. Usually the logit function is plot-ted against the log of the concentration of the toxi-cant, to yield a linear relationship.

lognormal distribution A positively skewed distribu-tion of a random variable which, when subjected to a logarithmic transformation, tends to take the shape of a normal distribution.

lordosis An anteroposterior curvature of the spine, gen-erally in the lumbar region. Also called hollow back or saddle back.

lotic Flowing water, such as rivers and streams.LT50 Time taken for 50% of the observed population to

die. Also known as median lethal time (MLT). See also ET50 and IT50.

lux A unit of illumination based on units per m2. One lux = 0.0929 foot candles and one foot candle = 10.76 lux.

lysimeter A laboratory column of selected representative soil or a protected monolith of undisturbed field soil with facilities for sampling and monitoring the move-ment of water and chemicals.

MAC See Maximum Allowable Concentration.macrocosm Large multi-species test system. See also

microcosm.macrophages A large phagocytic cell found in connec-

tive tissues, especially in areas of inflammation.macroscopic (gross) pathology The study of tissue

changes which are visible to the naked eye.malignancy A cancerous growth. A mass of cells

showing both uncontrolled growth and the tendency to invade and destroy surrounding tissues.

malignant See tumour and malignancy.manufacturer In the context of REACH means any

natural or legal person established within the Community who manufactures a substance within the Community.

manufacturing In the context of REACH means produc-tion or extraction of substances in the natural state.

margin of exposure Ratio of the no observed adverse effect level (NOAEL) for the critical effect to the theoretical, predicted or estimated dose or concentration. See also margin of safety.

margin of safety For some experts the margin of safety has the same meaning as the margin of exposure, while for other, the margin of safety means the

margin between the reference dose and the actual exposure dose or concentration. See also margin of exposure.

mass balance equation An equation that expresses the total mass of a chemical in terms of all the various forms and concentrations in different environmental compartments (including biota) in which it occurs. See also Chapters 3 and 7.

MATC See Maximum Acceptable Toxicant Concentration.

maximum acceptable toxicant concentration (MATC) The hypothetical toxic threshold concentration lying in a range bounded at the lower end by the high-est tested concentration having no observed effect (NOEC) and at higher end by the lowest tested con-centration having a significant toxic effect (LOEC) in a life cycle (full chronic) or partial life cycle (partial chronic) test. This may be represented as NOEC < MATC < LOEC. The MATC may be calculated as the geometric mean of the LOEC and NOEC. Calculation of an MATC requires quantitative life cycle toxicity data on the effects of a material on survival, growth, and reproduction.

maximum allowable concentration (MAC) Regulatory value defining the concentration which if inhaled daily (for workers: 8 h/d over a working week of 40 h, for the general population: 24 h) does not appear capable of causing appreciable harm in the light of present knowledge. See also threshold limit value.

measurement endpoint Measurable (ecological) charac-teristic that is related to the valued characteristic cho-sen as an assessment point.

measurement error Error that results from inaccuracy and imprecision in the measurement of parameter values.

median effective concentration (EC50) The concen-tration of the material in water to which test organ-isms are exposed that is estimated to be effective in producing some sublethal response in 50% of the test organisms. The EC50 is usually expressed as a time dependent value (e.g., 24-h or 96-h EC50). The sublethal response elicited from the test organisms as a result of exposure to the material must be clearly defined. For example, test organisms may be immo-bilized, lose equilibrium, or undergo physiological or behavioural changes.

median effective dose (ED50) The exposure dose of material estimated to be effective in producing some sublethal response in 50% of the test organisms. It is appropriately used with test animals such as rats, mice, dogs, but it is rarely applicable to aquatic

656 Glossary

organisms because it indicates the quantitative of a material introduced directly into the body by injection or ingestion rather than concentration of the material in water in which aquatic organisms are exposed dur-ing toxicity tests.

median effective time (ET50) The time required for half of the organisms in a toxicity test to exhibit a given nonlethal response end point at a given exposure con-centration.

median lethal concentration (LC50) The concentration of material in air, water, soil or sediment to which test organisms are exposed which is estimated to be lethal to 50% of the test organisms. The LC50 is usu-ally expressed as a time-dependent value (e.g. 24-h or 96-h LC50; the concentration estimated to be lethal to 50% of the test organisms after 24 or 96 h of expo-sure). The LC50 may be derived by observation (i.e. 50% of the test organisms can be seen to be dead at a given test concentration), by interpolation (i.e. more than 50% of the test organisms died at one test con-centration and fewer than 50% of the test organisms died at a lower test concentration, and the LC50 is estimated by interpolation between these two data points), or by calculation (i.e. the LC50 is statistical-ly derived by analysis of mortality data from a series of test concentrations).

median lethal dose (LD50) The dose of material that is estimated to be lethal to 50% of the test organisms. It is suitable for use with test animals such as rats, mice and dogs, but it is rarely applicable to aquatic organisms because it indicates the quantity of a mate-rial introduced directly into the body by injection or ingestion rather than the concentration of the material in water to which aquatic organisms are exposed dur-ing toxicity tests. The LD50 has often been used to classify and compare toxicity between chemicals but its value for this purpose is doubtful. One commonly used classification of this type is:

median tolerance limit (TLm or TL50) The concen-tration of material in air, water, sediment or soil at which 50% of the test organ-isms survive after a specified time of exposure. The TL50 (equivalent to the TLm) is usually expressed as a time-dependent value (e.g. 24-h or 96-h TL50; the estimated concen-tration at which 50% of test organisms survive after 24 or 96 h of expo-sure). Unlike lethal concentration and lethal dose, the term tolerance limit is applicable in designating the level of any measurable lethal con-dition (e.g., extremes in pH, temperature, dissolved oxygen). TLm and TL50 have been replaced by medi-an lethal concentration (LC50) and median effective

concentration (EC50).medulla The central portion of an organ or tissue, such

as the medulla of the mammalian kidney or a plant thallus; bone marrow and pith (adjective: medullary).

meiofauna Animals living in interstices of soil or sedi-ment of aquatic systems

mesocosm See microcosm.mesothelioma A malignant tumour of the mesothelium

of the pleura, pericardium or peritoneum, arising as a result of the presence of asbestos or caused by expo-sure to mining or smelting processes.

meta-analysis The process of using statistical methods to combine the results of different studies. In the biomedical sciences, the systematic evaluation of a problem using information (commonly in the form of statistical tables and other data) from a number of independent studies. A common application is the pooling of results from a number of small rand-omized controlled trials, none in itself large enough to demonstrate statistically significant differences, but, capable of doing so in aggregate. Meta-analysis has a qualitative component, i.e. application of prede-termined quality criteria (e.g. completeness of data, absence of bias) and a quantitative component, i.e. integration of numerical information. Meta-analy-sis includes overview and data pooling aspects, but implies more than either of these processes. Meta-analysis carries the risk of several biases reinforcing each other.

metabolic activation The biotransformation of relatively inert chemicals to biologically reactive metabolites.

metabonomics Techniques available to identify the pres-ence and concentrations of metabolites in a biological sample.

MFO See mixed function oxidase.microcosm Artificial multi-species test system that simu-

lates major characteristics of the natural environment for the purposes of ecotoxicological effects and risk assessment. Such systems are normally terrestrial or aquatic and may contain plants, animals (vertebrates and invertebrates) and micro-organisms. The terms mesocosm and macrocosm are used to refer to larger and more complex systems than microcosms but the distinction is often not clearly defined. See Chapter 7.

Microtox A test involving the “luminous” marine bacte-rium Photobacterium phosphoreum. Changes in light output are taken as indications of stress.

migration (population) The movement of an individual or group into or out of a new population or geograph-ical region.

Glossary 657

mineralisation The breakdown of a chemical substance or organic matter by micro-organisms in the presence of oxygen to carbon dioxide, water and mineral salts of any other elements present.

minimum significant difference (MSD) The difference between groups (in tests with e.g. salmonoid fish, the difference in average weights or average mortality) that would have to occur before it could be concluded that there was a significant difference between the groups. The MSD is provided by Dunnett’s multiple-range test, a standard statistical procedure.

MIT See IT50.mixed function oxidase An enzyme that catalyzes reac-

tions between an organic compound and molecular oxygen in which one atom of the oxygen molecule is incorporated into the organic compound and one atom of the oxygen molecule is reduced to water. Involved in the metabolism of many natural and xenobiotic compounds giving both unreactive products and prod-ucts of different or increased toxicity from that of the parent compound (phase-I reactions). See Chapter 3.

mixing zone An area where an effluent discharge under-goes initial dilution and is extended to cover the sec-ondary mixing in the ambient water body. A mixing zone is an allocated impact zone where water quality criteria can be exceeded as long as acutely toxic con-ditions are prevented.

model A formal representation of some component of the world or a mathematical function with parameters which can be adjusted so that the function closely describes a set of empirical data. A mathematical or mechanistic model is usually based on biological, chemical or physical mechanisms, and its parameters have real world interpretations. By contrast, statistical or empirical models are curve-fitted to data where the mathematical function used is selected for its numeri-cal properties. Extrapolation from mechanistic mod-els (e.g. pharmacokinetic equations) usually carries higher confidence than extrapolation using empiri-cal models (e.g. the logistic extrapolation models). A model that can describe the temporal change of a system variable under the influence of an arbitrary “external force” is called a dynamic model. To turn a mass balance model into a dynamic model, theories are needed to relate the internal processes to the state of the system, expressed e.g. in terms of concentra-tions. The elements required to build dynamic models are called process models.

model error The element of uncertainty associated with the discrepancy between the model and the real world.

mole The SI (Système International) metric unit for reporting amounts of chemicals whose relative molecular mass is known. One mole of a chemical is Avogadro’s number (6.023 x 1023) of molecules of that chemical. Metric mass-based units can be con-verted to molar units by dividing the former by the grammolecular weight of the chemical in question. Molarity refers to the number of moles of chemical per litre of solution and is denoted as M.

molecular descriptor A molecular descriptor is a struc-tural or physicochemical property of a molecule, or part of a molecule, which characterises a specific aspect of a molecule and is used as an independent variable in a QSAR.

molecular orbital Like atomic orbitals for single atoms, molecular orbitals are the energy levels in a molecule that can be occupied by (pairs of) electrons. Besides an energy level, these molecular orbitals have a specific spatial arrangement (more accurately, a specific spatial distribution of the electron density), and can thus be viewed as relatively localised to a certain part of a molecule. For example the Lowest Unoccupied Molecular Orbital (LUMO), is one of the most important energy levels in reactions where electrons or electron pairs are accepted, has both an energy level, which dictates whether a reaction is feasible or not, and a “localisation” which dictates whether it is accessible, and if so, where the reaction centre is. In most quantum-chemical formulations, molecular orbitals are constructed as minimum-energy, self-consistent linear combinations of atomic orbitals, with the atomic orbitals taken from the constituent atoms.

monitoring Long-term, standardised measurement, eval-uation, and reporting of specified properties of the environment, in order to define the current state of the environment, and to establish environmental trends. Surveys and surveillance are both used to achieve this objective.

monitoring test A test designed to be applied on a rou-tine basis, with some degree of control, to ensure that the quality of an environmental compartment, bio-logical endpoint or effluent has not exceeded some prescribed criteria range. In a biomonitoring test, organisms are used as “sensors” to detect changes in the quality of water or effluent. A monitoring test implies generation of information, on a continuous or other regular basis.

monomer Means a substance which is capable of form-ing covalent bonds with a sequence of additional like or unlike molecules under the conditions of the rele-

658 Glossary

vant polymer-forming reaction used for the particular process.

mono-oxygenase See mixed function oxidase.Monte Carlo simulation A technique used to obtain

information about the propagation of uncertainty in mathematical simulation models. It is an iterative process involving the random selection of model parameter values from specified frequency distribu-tions, simulation of the system, and output of predict-ed values. The distribution of the output values can be used to determine the probability of occurrence of any particular value, given the uncertainty in the parameters.

multigeneration study A toxicity test in which at least three generations of the test organism are exposed to the chemical being assessed. Exposure is usually continuous.

multivariate analysis Multivariate analysis is the anal-ysis of multi-dimensional data matrices by using statistical methods. Such data matrices can involve multiple dependent and/or independent variables.

mutagenesis Introduction of hereditary changes (muta-tions) in the genotype of a cell as a consequence of genetic alterations or the loss of genes or chromo-somes (or parts of them). Any chemical that causes mutations is said to be mutagenic. Some mutagenic chemicals are also carcinogenic. See also carcinogen-esis and transformation.

nanoscale Having one or more dimensions of the order of 100 nm or less.

nanoscience The study of phenomena and manipulation of materials at atomic, molecular and macromolecu-lar scales, where properties differ significantly from those at a larger scale.

nanotechnology The design, characterization, production and application of structures, devices and systems by controlling shape and size at the nanoscale.

nanomaterial Material with one or more external dimen-sions, or an internal structure, which could exhibit novel characteristics compared to the same material without nanoscale features.

nanoparticle Particle with two or more dimensions at the nanoscale.

nanocomposite Composite in which at least one of the phases has at least one dimension on the nanoscale.

nanostructured Having a structure at the nanoscale.narcosis Narcosis is a non-specific mode of toxic

action, normally associated with a reduction in cen-tral nervous system activity (and hence anaesthesia) and ultimately death. The effect is brought about by non-reactive chemicals and is thought to result from

an accumulation of the toxicant in cell membranes, diminishing their functionality. The narcotic effect is reversible, so that an organism will recover when the toxicant is removed. Narcotic effects are strongly associated with molecular hydrophobicity and hence good relationships have been found between the acute toxicity of narcotics and log Kow. Within the narcotic mode of toxic action, a number of mechanisms are often been distinguished. These mechanisms, which are especially apparent in environmental species, include non-polar narcosis, polar narcosis, amine nar-cosis, ester narcosis, as well as other narcotic mecha-nisms that have yet to be determined.

necropsy Examination of the organs and body tissues of a dead animal to determine the cause of death or any pathological condition.

necrosis Cell death or death of areas of tissue, usu-ally indicating that the affected tissue is surrounded by healthy tissue. Necrosis may be due to chemical agents acting locally, or secondary to physiological insult, infection or loss of circulation.

nematocide See pesticide.neonate A newly-born or newly-hatched individual (e.g.

first instar daphnid, < 24 h old).neoplasm A genetically altered, relatively autonomous

growth of tissue. A neoplasm is composed of abnor-mal cells, the growth of which is more rapid than that of other tissues and is not coordinated with the growth of other tissues.

nephrotoxity Toxicity to the kidney.neurotoxic Any toxic effect on any aspect of the central

or peripheral nervous system. Such changes can be expressed as functional changes (such as behavioral or neurological abnormalities) or as neurochemical, biochemical, physiological or morphological chang-es.

new chemicals In the EC, those produced since 1981 and not listed on the EINECS.

NIMBY principle Public acceptance of necessary provi-sions (e.g. waste incinerators) provided they do not affect the individual’s quality of life (NIMBY = not in my backyard).

NMR Nuclear Magnetic Resonance, a technique to identify atoms in a sample by measuring the signal given off by the relaxation of e.g. protons previously aligned in a strong magnetic field.

no observed adverse effect level (NOAEL) See no observed effect concentration.

no observed effect concentration (NOEC) The high-est concentration of a material in a toxicity test that has no statistically significant adverse effects on the

Glossary 659

exposed population of test organisms compared with the controls. When derived from life cycle or par-tial life test, it is numerically the same as the lower limit of the MATC. Also called no observed effect level (NOEL) or no observed adverse effect level (NOAEL).

no observed effect level (NOEL) See no observed effect concentration.

NO(A)EL No observed (adverse) effect level. See N(O)EC.

N(O)EC No (observed) effect concentration. The highest concentration of a test substance to which organisms are exposed, that does not cause any observed and statistically significant adverse effects on the organ-ism compared with the controls. For example, the NOEC might be the highest tested concentration at which an observed variable, such as growth, did not differ significantly from growth in the control. The NOEC customarily refers to sublethal effects, and to the most sensitive effect unless otherwise speci-fied. NEL, NOAEL, NEC and NOEC are equivalent terms.

non-genotoxic carcinogen A substance that causes cancer, not primarly damaging the genetic material, but by mechanisms that stimulate cell proliferation, thus increasing the chances for natural mutations to be produced, and/or selection of specific cell popula-tions that may derange in a later stage.

non-target organisms Those organisms which are not the intended targets of a particular use of a pesticide.

normal distribution The classical statistical bell-shaped distribution which is symmetric and parametrically simple in that it can be fully characterized by two parameters: its mean and variance. A normal distri-bution is observed in situations where many inde-pendent additive effects influence the values of the variates.

not chemically modified substance in the context of REACH means a substance whose chemical structure remains unchanged, even if it has undergone a chemi-cal process or treatment, or a physical mineralogical transformation, for instance to remove impurities.

notified substance According to REACH a notified substance for which a notification has been submitted and which could be placed on the market in accordance with Directive 67/548/EEC. See also new chemical.

nucleophilicity Nucleophilicity refers to the molecular or substructural property of having a repulsion for elec-trons or an attraction for positive charge. Molecular nucleophilicity is often described by the energy of the

highest occupied molecular orbital (EHOMO) and by superdelocalisabilities.

nucleotide In this case the basic building block of DNA and RNA: a base/sugar/phosphate complex, these nucleotides from a codon, coding for one amino acid.

occupational hygiene An applied science concerned with the recognition, evaluation and control of chemi-cal, physical and biological factors arising in or from the workplace which may affect the health or well-being of those at work or in the community.

octanol-water partition coefficient (Kow) The ratio of a chemical’s solubility in n-octanol and water at equi-librium; also expressed as P. The logarithm of Kow or P (i.e. log Kow or log P) is used as an indication of a chemical’s propensity for bioconcentration by aquatic organisms or skin permeability (see also Chapters 9 and 10).

ocular Relating to the eye.OECD Organization for Economic Co-operation and

Development.oligotrophic Nutrient poor (aquatic) system. See also

eutrophic.oncogene A retroviral gene that causes transformation of

the infected mammalian cell. Oncogenes are slightly changed equivalents of normal cellular genes called protooncogenes. The viral version is designated by the prefix v, the cellular version by the prefix c.

one-hit model Dose-response model of the form P(d)=1-exp(-bd) where P(d) is the probability of cancer death from a continuous dose rate (d) and b is a con-stant. The one-hit odel is based on the concept that a tumour can be induced after a single susceptible tar-get or receptor has been exposed to a single effective unit dose of an agent.

operational conditions In the context of REACH these are conditions under which a manufacturing or use process takes place.

organelle A structure with a specialized function which forms part of a cell.

orifice An opening or aperture.palate The partition separating the nasal and oral cavi-

ties.parameter uncertainty The element of uncertainty asso-

ciated with estimating model parameters. It may arise from measurement or extrapolation.

parameterise The allocation of values to the variables.PARCOM Paris Commission.parenchymal cell A cell of the functional tissue of a

gland or an organ.parthenogenesis Process by which eggs develop without

fertilization.

660 Glossary

particulate organic carbon (POC) The fraction of the organic carbon pool that is not dissolved in water, but is retained on a 0.45 µm glass fibre filter. POC is identical to suspended organic carbon (SOC) and is composed of plant and animal organic carbon and organic coatings on silt and clay.

particulate organic matter (POM) it is analogous to POC (see POC) but it refers to the entire organic pool that is not dissolved in water.

partition coefficient A partition coefficient is the ratio of the concentrations of a substance between two phases when the heterogeneous system of two phases is in equilibrium. In QSAR analysis, the octanol-water par-tition coefficient (log Kow) is often used as a descrip-tor of hydrophobicity, where K = [chemical]octanol / [chemical]water, by using a logarithmic relationship, K becomes an additive property, Log Kow = log [chemical]octanol - [chemical]water. See Chapters 3, 4, 9 and 10.

parts per billion (ppb) One unit of chemical (usually expressed as a mass) per 1,000,000,000 (109) units of the medium (e.g. water) or organism (e.g. tissue) in which it is found. For water, the ratio commonly used is micrograms of chemical per litre of water, 1 μg/L= 1 ppb; for tissues, 1 μg/kg = 1 ng/g = 1 ppb.

parts per million (ppm) One unit of chemical (usually expressed as a mass) per 1,000,000 (106) units of the medium (e.g. water) or organism (e.g. tissues) in which it occurs. For water, the ratio commonly used is milligrams of chemical per litre of water, 1 mg/L = 1 ppm; for tissues, 1 mg/kg = 1 μg/g = 1 ppm.

parts per thousand (ppt) One unit of chemical (usu-ally expressed as a mass) per 1000 (103) units of the medium (e.g. water) or organism (e.g. tissues) in which it occurs. For water, the ratio commonly used is grams of chemical per litre of water, 1 g/L = 1 ppt; for tissues, 1 g/kg = 1 ppt. This ratio is also used to express the salinity of seawater, where the grams of salt per litre of water is denoted by the symbol ppt. Full-strength seawater is approximately 35 ppt.

parts per trillion (pptr) One unit of chemical (usually expressed as a mass) per 1,000,000,000,000 (1012) units of the medium (e.g. water) or organism (e.g. tis-sues) in which it is found. The ratio commonly used is nanograms of chemical per litre of water, 1 ng/L = 1 pptr; for tissues, 1 ng/kg = 1 pptr.

PBPK Physiologically-based pharmacokinetic model.PCA Principal component analysis. A multivariate tech-

nique to derive a set of orthogonal parameters (prin-cipal components) from a large number of properties.

PEC Predicted environmental concentration. The esti-

mated concentration of a chemical in a particular medium at a particular location at a particular time. The PEC can be based on either measured or calcu-lated data. See Chapters 1, 4 and 12.

perceived risk See risk perception.percentiles Divides frequency distribution into 100 equal

portions. Hence the 95 percentile is the value that 95% of the population does not exceed.

permissible exposure limit (PEL) See threshold limit value (TLV).

peroxisome A cytoplasmic organelle present in animal and plant cells, which contains catalase and other peroxidase oxidative enzymes.

persistence Attribute of a substance which describes the length of time that the substance remains in a partic-ular environment before it is physically removed or chemically or biologically transformed.

pesticide A chemical used in agriculture and in other non-agricultural areas, to control the severity and incidence of pests and diseases which would other-wise reduce agricultural yields or hinder other proc-esses. Pesticides are used to control bacteria, fungi, algae, higher plants, nematodes, mollusca, mites and ticks, insects, rodents (e.g. mice and rats) and other organisms. This generic term is also used to cover: bactericides, fungicides, algicides, herbicides, nema-tocides, molluscicides, acaricides, insecticides and rodenticides.

pH The negative logarithm of the activity of hydrogen ions in gram equivalents per litre. The pH value expresses the degree or intensity of both acidic and alkaline reactions on a scale from 0 to 14, with 7 representing neutral, numbers less than 7 signifying increasingly acidic reactions, and numbers greater than 7 indicating increasingly basic or alkaline reac-tions.

phagocytosis The ingestion of microorganisms, cells, and foreign particles by phagocytes; hence phago-cytic macrophages.

pharmacodynamics Process of interaction of pharmaco-logically active substances with target sites, and the biochemical and physiological consequences leading to therapeutic or adverse effects. Also known as toxi-codynamics, but this term strictly refers to the study of substances other than drugs.

pharmacokinetics Process of uptake of drugs by the body, the biotransformation they undergo, the dis-tribution of the drugs and their metabolites in the tissues, and the elimination of the drugs and their metabolites from the body. Both the amounts and the concentrations of the drugs and their metabolites are

Glossary 661

studied. The term has essentially the same meaning as toxicokinetics and biokinetics, but this term strictly refers to the study of substances other than drugs.

phase-I reactions Enzymic modification of a xenobi-otic by oxidation, reduction, hydrolysis, hydration, dehydrochlorination or other reactions catalyzed by enzymes of the cytosol of the endoplasmatic reticu-lum (microsomal enzymes) or other cell organelles. See also MFO.

phase-II reactions Binding of a substance or its metabo-lites from a phase-I reaction with endogenous mol-ecules (conjugation) to create more watersoluble derivatives which can be excreted in the urine or bile. See Chapter 3.

phase-in substance In the context of REACH means a substance which meets at least one of the follow-ing criteria: (a) it is listed in the European Inventory of Existing Commercial Chemical Substances (EINECS); (b) it was manufactured in the Community, or in the countries acceding to the European Union on 1 January 1995 or on 1 May 2004, but not placed on the market by the manufacturer or importer, at least once in the 15 years before the entry into force of this regulation, provided the manufacturer or importer has documentary evidence of this; (c) it was placed on the market in the Community, or in the countries acced-ing to the European Union on 1 January 1995 or on 1 May 2004 before entry into force of this Regulation by the manufacturer or importer and was considered as having been notified in accordance with the first indent of Article 8(1) of Directive 67/548/EEC but does not meet the definition of a polymer set out in this Regulation, provided the manufacturer or import-er has documentary evidence of this.

phenology Life history.phenotype Total of observable features of an organism,

as the result of interaction between the genetic mate-rial (genotype) and the environment.

photodegradation Any breakdown reaction of a chemi-cal that is initiated by sunlight (ultraviolet light), or more accurately, by the influence of a high-energy photon. This can be either by direct photodegrada-tion, in which the photon photolysis or ionises the relevant molecule itself, which then reacts with other species in its vicinity, or by indirect photodegrada-tion, in which the relevant molecule reacts with ions or radicals created by photolysis of other species.

photoperiod The duration of illumination and darkness over a 24-h day.

placing on the market In the context of REACH means supplying or making available, whether in return for

payment or free of charge, to a third party. Import shall be deemed to be placing on the market.

PLS Partial least square analysis. A multivariate tech-nique to relate Y values for a series of objects to a set of X variables for the same objects.

PMN Premanufacture notification. Regulation for new chemicals as required by the Toxic Substances Control Act in the US. See also Chapter 13.

PNEC Predicted no effect concentration: environmen-tal concentration which is regarded as a level below which the balance of probability is that an unaccept-able effect will not occur. See Chapters 1, 7 and 12.

p.o. Abbreviation for oral administration (per os).point source Emission source(s), either single or mul-

tiple, which can be quantified by means of location and the amount of substance emitted per source and emission unit (e.g. amount per time unit).

pollutant A potentially harmful agent occurring in the environment, products or at the workplace as a result of human activities.

pollution Release to the environment of a chemical, physical, or biological agent that has the potential to damage the health of human or other organisms.

polymer In the context of REACH means a substance consisting of molecules characterised by the sequence of one or more types of monomer units. Such mol-ecules must be distributed over a range of molecu-lar weights wherein differences in the molecular weight are primarily attributable to differences in the number of monomer units. A polymer comprises the following: a) a simple weight majority of molecules containing at least three monomer units which are covalently bound to at least one other monomer unit or other reactant; b) less than a simple weight major-ity of molecules of the same molecular weight. In the context of this definition a “monomer unit” means the reacted form of a monomer substance in a polymer.

polymerase chain reaction Technique enabling a rapid multiplication of selected parts of a DNA and RNA strand.

polymorphism In this context, the existence of inter-individual differences in DNA sequences coding for one specific gene. The effects of such differences may vary dramatically, ranging from no effect at all to the building of inactive proteins, or not even build-ing the protein.

POM Particulate organic matter. See also TOC.population A group of interacting and, typically, inter-

breeding organisms (sharing genes) of the same spe-cies.

population biomass The total mass or weight of organ-

662 Glossary

isms in a population, given by the sum of the masses (or weights) of all the individual members of the pop-ulation.

population growth rate The relative increase in the pop-ulation per unit of time.

population size The total number of organisms in a pop-ulation.

pore water (or interstitial water) Water found in spaces between particles of soil or sediment.

porous pot test Biodegradation test that simulates the continuous activated sludge (sewage treatment) sys-tem.

potentiation The effect of a chemical which enhances the toxicity of another chemical. See also synergism.

power of a test The power of a statistical test is the prob-ability of rejecting the zero-hypothesis when it is false and the alternative hypothesis is correct.

precision A measure of the degree of agreement among individual results obtained from the same or identi-cal specimens with the same method and by the same analyst and laboratory.

precautionary principle The general principle by which all that can reasonably be expected is done to prevent unnecessary risks. See also ALARA and Chapter 1.

precipitation (1) The formation of a solid (i.e. precipi-tate) from a solution and (2) rain, snow, etc. formed by condensation of water vapour in air.

predicted environmental concentration (PEC) The concentration of a chemical in the environment, cal-culated on the basis of available information on cer-tain of its properties, its use and discharge patterns and the quantities involved.

predicted no effect concentration (PNEC) See PNEL.predicted no effect level (PNEL) The maximum level

(dose or concentration) which on the basis of current knowledge is likely to be tolerated by an organism without producing any adverse effect.

predictive risk assessment A risk assessment performed for a proposed future action, such as the use of a new chemical or the release of a new effluent.

predictivity The predictivity (or predictive capacity/abil-ity) of a model is a measure of its ability to make reli-able predictions for chemical structures not included in the training set of the model.

preliminary test See screening test.preparation means a mixture or solution composed of

two or more substances.primary biodegradation The structural change (trans-

formation) of a chemical substance by micro-organ-isms resulting in the loss of chemical identity.

probability A quantitative statement about the likelihood

of a specific outcome. Probability values can range from 0 to 1.0.

probit A probit, or probability unit, is obtained by modi-fying the standard variate of the standardized normal distribtion by the addition of a constant value of 5 (to avoid negative numbers). Converting a cumula-tive percent response to probits followed by plotting it against concentration or dose can provide useful information about the distribution of the response and estimates of the L(E)D50 or L(E)C50 values. This transformation is used for the analysis of dose-response data.

probit/log transform The probability unit obtained from the standardized normal distribution plotted against the logarithm of the concentration or dose of a sub-stance when a quantal or graded response has been measured. A linear plot provides evidence that the distribution is lognormal. Estimates of the L(E)C50 and L(E)D50, as well as the standard deviation for the distribution, can then be made.

producer of an article In the context of REACH: means any natural or legal person who makes or assembles an article within the Community.

product and process orientated research and devel-opment (PPORD) In the context of REACH means any scientific development related to product devel-opment, the further development of a substance, on its own, in preparations or in articles in the course of which pilot plant or production trials are used to develop the production process and/or to test the fields of application of the substance.

product use category Preparations or articles used for the same purpose (technical function, service, convenience …) and hence likely to be used under comparable conditions for which the same exposure scenario may then be applicable. See also exposure scenario.

prokaryote Simple unicellular organism, primarily bac-teria and cyanobacteria, that have no nuclei to contain their genetic material. They have a few subcellular structures. See also eukaryote.

proliferation Multiplication, i.e. an increase by frequent and repeated reproduction or growth by cell division.

promoter In carcinogenesis this is an agent which enhances tumour growth caused by a chemical after exposure to an initiator. See also initiation/initiator.

protein binding The process by which drugs and toxins are bound to proteins other than the receptor in the plasma or, less commonly, intracellularly. The bound fraction is inactive but in equilibrium with the free fraction in the cell or plasma.

Glossary 663

proteomics Techniques available to identify the proteins in a biological sample.

public health impact assessment Applying risk assess-ment to a specific target population. The size of the population needs to be known. The end product will be a quantitative statement about the number of peo-ple affected in this specific target population.

pulmonary alveoli Minute thin-walled air sacs, sur-rounded by bloodvessels. Found in the lungs of ver-tebrates.

QSAR See quantitative structure-activity relationship.quality assurance (QA) A programme organized and

designed to provide accurate and precise results. Included are selection of proper technical methods, tests, or laboratory procedures; sample collection and preservation; selection of limits; evaluation of data; quality control; and qualifications and training of per-sonnel.

quality control (QC) Specific actions required to pro-vide information for the quality assurance program. Included are standardization, calibration, replicates, and control and check samples suitable for statistical estimates of confidence of the data.

quality criteria Quality guidelines based on the evalua-tion of scientific data.

quality guidelines Numerical limits or text statements established to support and maintain designated uses of the environment or to protect human health.

quality objectives Numerical limits or narrative state-ments established to protect and maintain human health or designated uses of the environment at a par-ticular site.

quality standards Fixed upper limits for exposure to certain chemicals recognized under law by one or more levels of government. Well-known examples include the air, water and soil quality standards, as well as threshold limit values for air pollutans in the workplace.

quantal effect Discontinuous response such as death or survival or the presence/absence of a behavioural response. See continuous effect.

quantitative structure-activity relationship (QSAR) The relationship between the physical and/or chemi-cal properties of substances and their ability to cause a particular effect, enter into certain reactions, etc. See also Chapters 9-11.

quantitative structure-activity relationship (QSAR) A quantitative structure-activity relationship is a quanti-tative relationship between a biological activity (e.g. toxicity) and one or more descriptors that are used to predict the activity. See also Chapters 9-11.

quantitative structure-property relationship (QSPR) A quantitative structure-property relationship is quantitative relationship between a physicochemical property or environmental parameter (e.g. a partition coefficient) and one or more descriptors that are used to predict the property See also Chapters 9 and 10.

quantum-chemical parameters In principle, anything that can be derived from the results (mostly the densi-ty and eigenvector/eigenvalue matrix) of a quantum-chemical calculation for any atom or molecule. This includes basic parameters, such as the total energy or heat of formation of a molecule, overall molecular parameters, such as the electronegativity, hardness or dipole moment (or even the molecular surface area or volume, based on certain cut-off values for electron densities), orbital-specific parameters, such as the energy level of the highest occupied molecular orbital (HOMO); which is the same as the ionisation poten-tial) or lowest unoccupied molecular orbital (LUMO); also the electron affinity), or atom-based parameters, such as partial charge, superdelocalisability, self-polarisability, etc.

quotient method Calculation of the quotient of the measured or predicted environmental concentration (PEC) of a contaminant and the predicted no effect level (PNEL), used as an expression of hazard or risk. Higher quotients constitute greater evidence of a hazard or a greater risk. See also hazard quotient.

range-finding test See screening test.REACH Registration, Evaluation, Authorisation and

restriction of CHemicals. See Chapter 12.reasonable worst case Reasonably unfavourable but not

unrealistic situation. Combining the most adverse environmental circumstances and worst-case release parameters necessarily results in an unrealistic over-all worst-case estimation, which is extremely unlikely to occur.

receiving water Surface water (e.g. in a stream, river, or lake) that has received a discharged waste, or is about to receive such a waste (e.g. just upstream or up-cur-rent from the discharge point).

recipient of an article In the context of REACH means an industrial or professional user being supplied with an article but does not include consumers.

recipient of a substance or a preparation In the context of REACH means a downstream user or a distributor being supplied with a substance or a preparation.

recommended limit A maximum concentration of a potentially toxic substance which is expected to be safe. Such limits often have no statutory basis, in which event any control or statutory limit should not

664 Glossary

be exceeded.reconstituted water De-ionized or glass-distilled water

to which reagent-grade chemicals have been added. The resultant synthetic fresh water will be free from contaminants and have the desired pH and hardness characteristics.

reference compound Standard substance whose known toxicological, ecotoxicological or physicochemical properties can be used to check the results of a test.

reference dose An estimate of the daily exposure dose that is likely to be without deleterious effect even if continued exposure occurs over the lifetime. See also acceptable daily intake.

reference environment A generalized description of the environment into which contaminants will be released and in which organisms will be exposed. Reference environments are used when there is no specific site at risk.

reference site A relatively unpolluted site used for com-parison with polluted sites in environmental monitor-ing studies, often incorrectly referred to as a control site.

registrant In the context of REACH means the manufac-turer or the importer or the producer or importer of an article submitting a registration for a substance.

registrant’s own use In the context of REACH means an industrial or professional use by the registrant.

regression analysis A statistical procedure for determin-ing the constants and coefficients in regression equa-tions from an analysis of observed data for two or more variables. See also regression coefficient.

regression coefficient A parameter which describes the rate of change of a dependent variable relative to an independent variable; any coefficient in a regression equation, such as the parameters a and b in the lin-ear regression equation y = a+bx. See also regression analysis.

remediation Concerned with correction and clean-up of chemically contaminated sites.

renal Associated with the kidneys.replicate A single test unit, such as a container or aquar-

ium, containing a prescribed number of organisms exposed to one concentration or dose of the test com-pound. An aquatic toxicity test comprising five test concentrations and a control, with three replicates, would require 18 aquaria. For each concentration or control, there would be three aquaria or replicates. A replicate is an independent test unit, thus, any transfer of organisms or solutions from one replicate to anoth-er would invalidate the test.

reproducibility Measure of the extent to which different

laboratories obtain the same result with the same ref-erence test compound.

reproductive toxicology The study of the adverse effects of chemicals on the embryo, foetus, neonate and pre-pubertal animal and the adult reproductive and neuro-endocrine systems.

resistance time The period of time that an organism is able to live beyond the incipient lethal level.

response Change developed in the state or dynamics of an organism, system or (sub) population in reaction to exposure to an agent.

restriction In the context of REACH means any con-dition for or prohibition of the manufacture, use or placing on the market.

retrospective risk assessment A risk assessment per-formed for hazards that began in the past and may have ongoing effects, e.g. waste disposal sites and oil spills.

rhizosphere Zone of soil immediately surrounding the roots.

ribonucleic acid (RNA) A generic term for a group of nucleotide molecules, similar in composition to deox-yribonucleic acid (DNA), which perform a number of functions in programming the genetic code in cells. There are several types of RNA, e.g. messenger RNA, ribosomal RNA, transfer RNA.

ring test (1) A conjoint test conducted under strictly standardized and uniformly applied conditions to assess the precision and accuracy with which different laboratories can determine the toxicity of a chemical or effluent, and (2) a test designed to measure statistically the reproducibility of a test method, or to compare the results obtained from the use of different test methods.

risk The probability of an adverse effect in an organism, system or (sub) population caused under specified circumstances by exposure to an agent.

risk analysis (1) A process for controlling situations where an organism, system or (sub) population could be exposed to a hazard. The risk analysis process consists of three three components: risk assessment, risk management and risk communication, and (2) sometimes used as an equivalent term to risk assessment, especially in older literature.

risk assessment A process intended to calculate or estimate the risk to a given target organism, system or (sub) population, including the identification of attendant uncertainties, following exposure to a particular agent, taking into account the inherent characterizations of the agent of concern as well as the characterization of the specific target system. The

Glossary 665

risk assessment process includes four steps: hazard identification, hazard characterization (related terms: dose-response assessment and effect assessment), exposure assessment, and risk characterization. It is the first component in a risk analysis process.

risk-benefit analysis The next step after risk classifica-tion. It is the process of drawing up a balance sheet of the respective risks and benefits of a proposed risk-reducing action. It is a multidisciplinary task in which the risk manager has to consider not only the risk assessment but also other important aspects such as technical feasibility, economic factors, social and cultural factors as well as legislative and political fac-tors. See also Chapter 1.

risk characterization The qualitative and, wherever possible, quantitative determination, including attendant uncertainties, of the probability of occurrence of known and potential adverse effects of an agent in a given organism, system or (sub) population, under defined exposure conditions. Risk characterization is the fourth step in the risk assessment process.

risk classification The valuation (or weighting) of risks in order to decide whether risk reduction is required. It is a complex process of determining the signifi-cance or value of the identified hazards and estimated risks to those concerned with or affected by the deci-sion. It therefore includes the study of risk perception and the balancing of perceived risks and perceived benefits. See also risk evaluation.

risk communication Interactive exchange of informa-tion about health or environmental risks among risk assessors, managers, news media, interested groups and the general public.

risk estimation Quantification of the probability, includ-ing attendant uncertainties, that specific adverse effects will occur in an organism, system or (sub) population due to actual or predicted exposure.

risk evaluation Establishment of a qualitative or quantitative relationship between risks and benefits of exposure to an agent, involving the complex process of determining the significance of the identified hazards and estimated risks to the system concerned or affected by the exposure, as well as the significance of the benefits brought about by the agent. It is an element of risk management. Risk evaluation is synonymous with risk-benefit evaluation. See also risk classification.

risk management Decision-making process involving considerations of political, social, economic, and technical factors with relevant risk assessment infor-

mation relating to a hazard so as to develop, analyse, and compare regulatory and non-regulatory options and to select and implement appropriate regulatory response to that hazard.

risk management measures (RMMs) Measures in the control strategy for a substance that reduce the emis-sion and exposure to a substance, thereby reducing the risk to human health or the environment.

risk monitoring Process following up the decisions and actions within risk management in order to ascertain that risk containment or reduction with respect to a particular hazard is assured. Risk monitoring is an element of risk management.

risk perception An integral part of risk evaluation. The subjective perception of the gravity or importance of the risk based on the individual’s knowledge of dif-ferent risks and the moral and political judgement attached to them and their importance.

risk quotient A comparison of exposure with effects, i.e. the PEC/PNEC ratio. This risk quotient is often used to express the risk posed by a particular chemical. See also hazard quotient.

risk reduction Taking measures to protect man or the environment against the risks identified.

RMM Risk Management Measure.robustness A measure of intralaboratory day-to-day vari-

ation induced by small changes in procedure.robust study summary In the context of REACH

and the OECD Chemicals Program a robust study summary is a detailed summary of the objectives, methods, results and conclusions of a full study report providing sufficient information to make an independent assessment of the study minimising the need to consult the full study report.

rodenticide See pesticide.round-robin test Synonym for ring test.ruggedness A method’s reproducibility under the influ-

ence of variation in analyst, instrumentation, day of testing, and laboratory.

run-off The portion of the precipitate on the land that ultimately reaches streams and, eventually, the sea.

safe concentration Concentration of material to which prolonged exposure will cause no adverse effect.

safety Practical certainty that adverse effects will not result from exposure to an agent under defined cir-cumstances. It is the reciprocal of risk.

safety factor Composite (reductive) factor by which an observed or estimated no-observed-adverse-effect (NOAEL) is divided to arrive at a criterion or stand-ard that is considered safe or without appreciable risk. See also assessment factor and uncertainty factor.

666 Glossary

safety (toxicological) Defined as a high probability that adverse effects will not result from exposure to a sub-stance under specific conditions of quantity and man-ner of use.

salinity The total amount of salts, in g, dissolved in 1 kg of water. It is determined after all carbonates have been converted to oxides, all bromide and iodide have been replaced by chloride, and all organic matter has been oxidized. Salinity can also be measured directly using a salinity/conductivity meter or other means. It is usually reported in g/kg or parts per thousand.

SAM Standardized aquatic microcosm.saprophyte An organism that obtains its nutrients from

dead and decaying matter.SARA (US) Superfund Amendment and Reauthorization

Act.satellite groups In toxicity testing, organisms or groups

of organisms treated in a similar fashion for special additional studies.

SCAS test Biodegradation test to monitor the decay of DOC.

scientific research and development In the context of REACH means any scientific experimentation, analy-sis or chemical research carried out under controlled conditions in a volume less than 1 tonne per year.

screening test (preliminary test or range-finding test) (1) A test conducted to estimate the concentrations to be used for a definitive test, and (2) a short-term test used early in a testing programme to evaluate the potential of a chemical (or other substance) to produce a given adverse effect (e.g. mortality).

SDS Safety Data Sheetsecondary poisoning The product of biomagnification

and toxicity.semistatic Exposure system in which the test volume is

renewed at intervals during the study.sensitization Immune process whereby individuals

become hypersensitive to substances, pollen or other agents which then induce a potentially harmful aller-gy when they are subsequently exposed to the sensi-tizing material (allergen).

sister chromatid exchange A reciprocal exchange of DNA between the two DNA molecules of a replicat-ing chromosome.

site In the context of REACH means a single location, in which, if there is more than one manufacturer of (a) substance(s), certain infrastructure and facilities are shared.

small and medium enterprise (SME) In the context of REACH means small and medium-sized enterprises as defined in the Commission Recommendation of 6

May 2003 concerning the definition of micro, small and medium-sized enterprises.

sorption Term used instead of adsorption or absorption, when it is difficult to discriminate experimentally between these processes.

source term An estimate of the total amount released, or the temporal pattern of the rate of release of a pollut-ant from a source.

spawning The release of eggs or sperm from mature adult fish, or refers to behaviour related to the readi-ness of mature adult fish to release gametes.

speciation Determination of the exact chemical form or compound in which an element occurs in a sample, for example whether arsenic occurs in the form of trivalent or pentavalent ions or as part of an organic molecule, and the quantitative distribution of the different chemical forms that may coexist.

specific exposure scenario An exposure scenario cover-ing one or a few specific uses or activities for which more specific restrictions of activities or more specif-ic risk management measures are needed, compared to a broad exposure scenario. See also exposure sce-nario.

specificity The ability to identify and quantify the target analyte in the presence of chemically similar interfer-ing compounds.

stable age distribution The abundance of relative age classes which a population approaches if it is allowed to grow exponentially.

standard An environmental quality standard is the limiting concentration of a chemical (or degree of intensity of some other adverse condition, e.g. pH) which is permitted in an environmental compartment (soil, effluent or waterway). Standards are established for regulatory purposes and are determined on the basis of a judgement of the criteria involved. The standard is dependent on the use (e.g. drinking water or agricultural water for irrigation). Standards are derived from criteria, often by applying safety factors (e.g. quality standards for air, water and soil).

static Exposure system in which the test volume is not renewed during the study.

static renewal Describes a toxicity test in which test solutions are renewed (replaced) periodically, usually at the beginning of each 24-h period. Synonymous terms are batch replacement, renewed static, renewal, static replacement and semi-static.

statistically significant effects Effects (responses) in the exposed population that are different from those in the controls at a statistical probability level of p < 0.05. Biological endpoints that are important for

Glossary 667

the survival, growth, behaviour and perpetuation of a species are selected as criteria. Endpoints differ depending on the type of toxicity test to be conducted and the species used. The statistical approach also depends on the type of toxicity test conducted.

steady-state The non-equilibrium state of a system in which matter flows in and out at equal rates so that all of the components remain at constant concentrations (dynamic equilibrium). In a chemical reaction, a component is in a steady-state if the rate at which the component is being synthesized (produced) is equal to the rate at which it is being degraded (used). In multimedia exposure models and bioaccumulation models it is the state at which the competing rates of input/uptake and output/elimination are equal. An apparent steady-state is reached when the concentration of a chemical remains essentially constant over time. Bioconcentration factors are usually measured at steady-state. See also equilibrium.

stochastic Due to, pertaining to or arising from chance and, hence, involving probability and obeying the laws of probability. The term stochastic indicates that the occurrence of effects so named, would be ran-dom. This means that, even for an individual, there is no threshold of dose below which the effect will not occur and the chance of experiencing the effect increases with increasing dose. Hereditary effects and cancer induced by radiation are considered to be sto-chastic effects.

stochastic analysis An analysis in which one or more parameters is represented by statistical distribution rather than a constant.

stochasticity Randomness determining or influencing a process. Variability in parameters or in models con-taining such parameters resulting from the inherent variability of the system described.

stochastic model A mathematical model founded on the properties of probability so that a given input pro-duces a range of possible outcomes which are due to random effects.

stock solution A concentrated aqueous solution of the substance to be tested. Measured volumes of a stock solution are added to dilution water to prepare the required strengths of test solutions.

stoichiometry The quantitative relationship between the elements in a compound or between the reactants and the products in a chemical reaction.

STP Sewage Treatment Plant.stress The proximate (or immediate) cause of an adverse

effect on an organism or system.

structural alert A structural alert is a molecular (sub)structure associated with the presence of a bio-logical activity.

structure-activity relationship (SAR) The correlation between molecular structure and biological/chemical/physicochemical activity. It is usually applied to the observation of the effect that the systematic structural modification of a particular chemical entity has on a defined biological, chemical or physicochemical end-point. See also QSAR and Chapters 9-11.

study summary In the context of REACH means a sum-mary of the objectives, methods, results and con-clusions of a full study report providing sufficient information to make an assessment of the relevance of the study for hazard assessment.

Sturm test Biodegradation test to measure CO2 produc-tion.

stygobiont Organism which lives only in groundwater.stygophile Organism which lives in groundwater and in

surface water.subacute See subchronic.subchronic Short-term tests that give an indication of

long-term effects, often by focusing on critical (or sensitive) stages. Sometimes referred to as subacute but, in the light of this definition, this would seem to be misleading. The period of exposure usually does not exceed 10% of the life span.

sublethal Below the concentration that causes immedi-ate death. Exposure to sublethal concentrations of a material may produce less obvious effects on the behaviour, biochemical and/or physiological func-tion, and histology of organisms.

substance In the context of REACH means a chemi-cal element and its compounds in the natural state or obtained by any manufacturing process, includ-ing any additive necessary to preserve its stability and any impurity deriving from the process used, but excluding any solvent which may be separated with-out affecting the stability of the substance or chang-ing its composition.

substances which occur in nature In the context of REACH means a naturally occurring substance as such, unprocessed or processed only by manual, mechanical or gravitational means; by dissolution in water, by flotation, by extraction with water, by steam distillation or by heating solely to remove water, or which is extracted from air by any means.

substructure A substructure is an atom, or group of adjacently connected atoms, in a molecule.

supplier of an article In the context of REACH means any producer or importer of an article, distributor or

668 Glossary

other actor in the supply chain placing an article on the market.

supplier of a substance or a preparation In the con-text of REACH means any manufacturer, importer, downstream user or distributor placing on the mar-ket a substance, on its own or in a preparation, or a preparation.

surfactant A surface-active subtance (e.g. a detergent) which reduces surface tension and facilitates disper-sion of substances in water. See also detergent.

surrogate A test organism, or population that is cultured under laboratory conditions to serve as a substitute in toxicity testing for indigenous organisms, communi-ties or populations.

surveillance Measurement of environmental or health characteristics over an extended period of time to determine status or trends in some aspect of environ-mental quality or human health.

survival time The time interval between initial exposure of an organism to a harmful chemical and death.

susceptibility The condition of organism or other eco-logical system lacking the ability to resist a particular disease, infection or intoxication. It is inversely pro-portional to the magnitude of the exposure required to cause the response.

synergism A phenomenon in which the toxicity of a mixture of chemicals is greater than that which would be expected from the total toxicity of the individual chemicals present in the mixture.

targeting of exposure assessment The targeting phase of the exposure assessment refines the scope of the exposure scenario: which target groups (worker, con-sumer, environment) are exposed and to what degree. Initial information on exposure is reviewed to identi-fy relevant exposure routes and exposure conditions. The targeting phase consists of the first two steps in the development of exposure scenarios: Step 1: Identification of uses; Step 2: Specification of manu-facturing or use conditions. It ends with the descrip-tion of the tentative exposure scenario. See Chapters 2, 4 and 12.

TDI See tolerable daily intake.tentative exposure scenario The tentative exposure

scenario forms the starting point for the exposure estimate and risk characterisation. A tentative exposure scenario is a set of assumptions (using the determinants of exposure) on how a process is conducted and which risk management measures that are used or should be implemented. See exposure scenario and Chapters 2, 5 and 12.

teratogen Agent which, when administered prenatally to

the mother, induces permanent structural malforma-tions or defects in the offspring.

teratogenesis The potential or capacity of a substance to cause defects in embryonic and foetal development.

terrestrial Relating to land, as distinct from water or air.test material A chemical, formulation, effluent, sludge,

or other agent or substance under investigation in a toxicity test.

test solution or test treatment Medium containing the material to be tested to which the test organisms will be exposed. Different test solutions contain different concentrations of the test material.

threshold Dose or exposure concentration of an agent below that a stated effect is not observed or expected to occur.

threshold-effect concentration (TEC) The concentra-tion calculated as the geometric mean of NOEC and LOEC. Chronic value or subchronic value are alterna-tive terms that may be appropriate depending on the duration of exposure in the test. The TEC is equiva-lent to the (maximum acceptable toxicant concentra-tion (MATC) used in other countries.

threshold limit value (TLV) Concentration in air of a substance to which it is believed that most workers can be exposed daily without adverse effect (the threshold between safe and dangerous concentrations). These values are established (and revised annually) by the American Conference of Governmental Industrial Hygienists and are time-weighted concentrations for a 7-h or 8-h working day and a 40-h working week. For most substances the value may be exceeded to a certain extent, provided there are compensating periods of exposure below the value during the working day (or in some cases, the week). For a few substances (mainly those that produce a rapid response) the limit is given as a ceiling concentration (maximum permissible concentration, designated by “C”) that should never be exceeded. See also maximum allowable concentration.

tiered testing strategy Sets out a structured approach to assessing the fate and effects of substances, where tests in higher tiers may be required depending upon the results of tests at earlier stages (i.e. lower tiers). Under a tiered structure, for example, data require-ments for effects testing might progress from acute to chronic laboratory studies to field studies.

time-independent (TI) test An acute toxicity test with no predetermined temporal endpoint. This type of test, sometimes referred to as a “threshold” or “incip-ient” lethality test, is allowed to continue until acute toxicity (mortality or a defined sublethal effect) has

Glossary 669

ceased or nearly ceased and the toxicity curve (plot of effect against time of exposure) indicates a threshold or incipient concentration. With most test materials, this point is reached within 7 to 10 d, but it may not be reached within 21 d. Practical or economic reasons may dictate that the test has to be stopped at this point and a test be designed for a longer period of time.

time-weighted average concentration (TWA) The con-centration of a substance to which a person is exposed in the ambient air, averaged over a period, usually 8 h. For example, if a person is exposed to 0.1 mg/m3 for 6 h and 0.2 mg/m3 for 2 h, the 8 h TWA will be (0.1 x 6 + 0.2 x 2) / 8 = 0.125 mg/m3.

TLV See threshold limit value.TOC Total organic carbon, often expressed as kg OC/

kg solid. The organic matter content of soil and sedi-ment is often determined by measurement of organic carbon. Typically, about half of all natural organic matter consists of carbon (OC ≈ 0.6 x OM).

tolerable daily intake (TDI) Analogous to an accepta-ble daily intake. The term tolerable is used for agents which are not deliberately added such as contami-nants in food.

tolerable intake Estimated maximum amount of an agent, expressed on a body mass basis, to which each individual in a (sub) population may be exposed over a specific period without appreciable risk.

tolerance The ability to experience exposure to poten-tially harmful amounts of a substance without show-ing an adverse effect.

topical Pertaining to a particular (skin) area, e.g. a topical effect, that involves only the area to which the causative substance has been applied.

total organic carbon (TOC) The sum of dissolved organic carbon (DOC) and particulate organic carbon (POC) or suspended organic carbon (SOC).

total organic matter (TOM) The sum of dissolved organic matter (DOM) and particulate organic matter (POM) or suspended organic matter (SOM).

toxic Able to cause injury to living organisms as a result of physicochemical interaction.

toxic endpoint A toxic endpoint is a measure of the del-eterious effect to an organism following exposure to a chemical. A large number of toxic endpoints are used in regulatory assessments of chemicals. These include lethality, generation of tumours (carcinogenicity), immunological responses, organ effects, development and fertility effects. It is the purpose of a toxicity test to determine whether a chemical has the potential to exhibit the toxic effect of interest, and in some cases, to determine relative potency. In QSAR analysis, it

is important to develop models for individual toxic endpoints, and different methods may be required for different endpoints.

toxicant An agent or material capable of producing an adverse response (effect) in a biological system, seriously injuring structure and/or function or producing death.

toxicity Inherent property of an agent to cause an adverse biological effect.

toxicity curve The curve obtained by plotting the median survival times of a group of test organisms against the concentration on a logarithmic scale.

toxicity equivalency factor (TEF) Factor used in risk assessment to estimate the toxicity of a complex mix-ture, most commonly a mixture of chlorinated diben-zo-p-dioxins, furans and biphenyls: in this case, TEF is based on relative toxicity to 2,3,7,8-tetra-chloro-dibenzo-p-dioxin.

toxicity identification evaluation (TIE) Describes a systematic pre-treatment sample (e.g. pH change, filtration, or aeration) followed by tests for toxicity. This evaluation is used to identify the agent(s) primarily responsible for lethal or sublethal toxicity in a complex mixture.

toxicity test Determination of the effect of a substance on a group of selected organisms under defined con-ditions. A toxicity test usually measures either the proportion of organisms affected (quantal), or the degree of effect shown (graded or quantitative), after exposure to specific levels of a stimulus (concentra-tion or dose, or mixture of chemicals).

toxicodynamics See pharmacodynamics.toxicokinetics See pharmacokinetics.toxic unit The strength of a chemical (measured in some

unit) expressed as a fraction or proportion of its lethal threshold concentration (measured in the same unit). The strength may be calculated as follows: toxic unit = actual concentration of chemical in solution / LC50. If this number is greater than 1.0, more than half of a group of organisms will be killed by the chemical. If it is less than 1.0, more than half the organisms will not be killed. 1.0 toxic unit = the incipient LC50.

Toxiguard Biomonitoring system comprising a sub-merged bed of continually developing microorgan-isms.

toxin Natural poison; a toxic organic substance produced by a living organism.

transcription Formation of mRNA, complementary to a string of DNA.

transcriptomics Techniques available to identify the mRNA from actively transcribed genes.

670 Glossary

transgenic animals Genetically engineered animals car-rying genes from a different species.

triggers/trigger values are criteria applied to results from tests (for fate or effects) which would prompt further studies, e.g. moving to the next tier.

TSCA (US) Toxic Substances Control Act.tumour (neoplasm) Growth of tissue forming an abnor-

mal mass. Cells of a benign tumour will not pread and cause cancer. Cells of a malignant tumour can spread through the body and cause cancer.

turbidity The extent to which the clarity of water has been reduced by the presence of suspended or other matter that causes light to be scattered and absorbed rather than transmitted (in straight lines) through the sample. It is generally expressed in terms of Nephelometric Turbidity Units.

ultimate aerobic biodegradation The breakdown of a chemical substance by micro-organisms in the pres-ence of oxygen to carbon dioxide, water and mineral salts of any other elements present (mineralisation) and the production of new biomass and organic microbial biosysnthesis products.

ultimate median tolerance limit The concentration of a chemical at which acute toxicity ceases. Also called the incipient lethal level, lethal threshold concentra-tion and asymptotic LC50.

UN United Nations.UNCED UN Conference on Environment and

Development (held in Rio de Janeiro (Brazil) in 1992).

uncertainty Imperfect knowledge concerning the present or future state of an organism, system or (sub) popu-lation under consideration.

uncertainty factor Reductive factor by which an observed or estimated no observed adverse effect level (NOAEL) is divided to arrive at the criterion or standard that is considered safe or without apprecia-ble risk. See also assessment factor and safety factor.

upstream water Surface water (e.g. in a stream, river or lake) which is not influenced by the effluent (or other test substance), because it is removed from the source in a direction against the current or sufficiently far across the current.

uptake The process of sorbing a test chemical substance into or onto the test organ-isms.

uptake rate constant The first-order one-compartment constant to describe the uptake of a chemical sub-stance by an organism from water.

use In the context of REACH means any processing, for-mulation, consumption, storage, keeping, treatment, filling into containers, transfer from one container to

another, mixing, production of an article or any other utilisation.

use and exposure category In the context of REACH means an exposure scenario covering a wide range of processes or uses where the processes or uses are communicated, as a minimum, in terms of the brief general description of use.

USES Uniform System for the Evaluation of Substances. See Chapter 12.

validation Process by which the reliability and relevance of a particular approach, method, process or assess-ment is established for a defined purpose. Different parties define “Reliability” as establishing the repro-ducibility of outcome of the approach, method, proc-ess or assessment over time. “Relevance” is defined as establishing the meaningfulness and usefulness of the approach, method, process or assessment for a defined purpose.

van der Waals forces weak mutual attractions between molecules which can contribute to bonding between atoms.

verification Comparison of predicted with measured val-ues, and the testing of assumptions and the internal logic of the model. This includes: (1) scientific veri-fication that the model includes all major and salient processes, (2) the processes are formulated correctly, and (3) the model suitably describes observed phe-nomena for the use intended.

wastewater A general term that includes effluents, lea-chates and elutriates.

weight composition The distribution of organisms among the various weight classes present in the popu-lation. The sum of individual weights over all weight classes equals the population biomass. See also popu-lation biomass.

WHO World Health Organization.WWTP Waste water treatment plant.xenobiotic A man-made chemical or material not pro-

duced in nature and not normally considered a con-stituent component of a specified biological system. This term is usually applied to manufactured chemi-cals.

xenobiotic metabolism The chemical transformation of compounds foreign to an organism by various enzymes present in that organism. See also biotrans-formation and xenobiotic.

year Per year in the context of REACH means per cal-endar year, unless stated otherwise, for phase-in sub-stances that have been imported or manufactured for at least three consecutive years, quantities per year shall be calculated on the basis of the average pro-

Glossary 671

duction or import volumes for the three preceding calendar years.

Zahn-Wellens test Biodegradation test to monitor the decay of DOC.

REFERENCES

1. Calow P. ed. 1993. Handbook of Ecotoxicology. Blackwell Scientific Publications, London, UK.

2. Duffus JH. 1993. Glossary for chem-ists of terms used in toxicology, IUPAC. Pure and Appl Chem 65:2003-2122.

3. Hodgson E, Mailman RB, Chambers JE. 1988. Macmillan Dictionary of Toxicology. Macmillan Press Ltd, London, UK.

4. Last JM. 1988. A Dictionary of Epidemiology. Oxford University Press, Oxford, UK.

5. Rand GM. 1995. Fundamentals of Aquatic Toxicology. 2nd ed. CRC Press, Washington, DC.

6. Richardson ML. 1990. Risk Assessment of Chemicals in the Environment. Royal Society of Chemistry, Cambridge, UK.

7. Stenesh J. 1989. Dictionary of Biochemistry and Molecular Biology. Wiley, New York, NY.

8. Suter GW. 1993. Ecological Risk Assessment. Lewis Publ, Chelsea, MI.

9. Organization for Economic Co-operation and Development. 2003. Description of selected key gener-ic terms used in chemical hazard/risk assessment. Joint project with IPCS on the harmonization of hazard/risk assessment terminology. OECD Environment, Health and Safety Publications. Series on Testing and Assessment 44. OECD, Paris, France.

10. Commission of the European Communities. 2006. Regulation (EC) No 1907/2006 of the European Parliament and of the Council of 18 December 2006 concerning the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH), establishing a European Chemicals Agency, amending Directive 1999/45/EC and repealing Council Regulation (EEC) No

793/93 and Commission Regulation (EC) No 1488/94 as well as Council Directive 76/769/EEC and Commission Directives 91/155/EEC, 93/67/EEC, 93/105/EC and 2000/21/EC. Off J Eur Union, L 396/1 of 30.12.2006.

11. Commission of the European Communities. 2005. Opinion on the appropriateness of existing methodolo-gies to assess the risks associated with engineered and adventitious products of nanotechnologies. Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR), Brussels, Belgium.

12. European Chemicals Bureau. 2005. Technical guid-ance document on preparing the chemical safety report under REACH. REACH Implementation Project 3.2. Report prepared by CEFIC, RIVM, the Federal Institute for Risk Assessment (BfR), Federal Institute for Occupational Safety and Health (BAuA), Ökopol, DHI Water & Environment and TNO Chemistry. European Commission, Joint Research Centre, Ispra, Italy (http://ecb.jrc.it/REACH/).

13. Organization for Economic Co-operation and Development. 2006. Guidance document on the vali-dation of quantitative structure-activity relationships-(Q)SARs. Appendix 1. Glossary of (Q)SAR terminology. OECD, Paris.

14. European Centre for Ecotoxicology and Toxicology of Chemicals. 2001. Genomics, transcript profiling, proteomics and metabonomics (GTPM). An introduc-tion. ECETOC Document No 42. ECETOC, Brussels, Belgium.

15. European Centre for Ecotoxicology and Toxicology of Chemicals. 2004.. ECETOC Technical Reports 90, 93 and 97. ECETOC, Brussels, Belgium.

16. National Research Council. 2006. Human Biomonitoring for Environmental Toxicants. National Academic Press, Washington, DC.

17. Zartarian V, Bahadori, T, McKone T. 2005. Adoption of an official ISEA glossary. J Exp Anal Environ Epidemiol 15:1-5.

672 Glossary

Abiotic factors, 114-121, 328-331, 639Abiotic transformation

databases, 414, 449-452experimental measurement, 121estimation, 403-408hydrolysis, 115, 404-408, 555oxidation, 115, 117-118photochemical degradation, 115, 119-121, 403, 662reduction, 115, 118-119

Absorbed dose, 227,639Absorption, 99-100, 229, 232-234, 438-40, 639Acceptable daily intake, 9, 20, 267, 361-362, 639Acclimatization, 121, 130, 639Accumulation

modifying factors, 97-101, 393-394, 639in earthworms, 111-113in fish, 90, 391-397in mammals and birds, 113-114in terrestrial invertebrates, 111-113in terrestrial plants, 106-111

Acid dissociation constant, 235Acidification, 284, 287Acute

single dose toxicity, 240-241, 295-298, 430-434tests, 240-242, 295-298, 430-434, 639toxicity, 240-242, 295-298, 430-434, 639

Adaptation, 121, 128, 409, 639Added risk, 639Additive

effect, 270-272, 332-335, 639toxicity, 270-272, 332-335, 639-640

Adenocarcinoma, 640Adenoma, 640ADI, see Acceptable daily intakeAdsorption, 74-79, 171-178, 315-316, 379-380, 385-

388, 640Adsorption coefficient, 76, 315-316, 379-380, 385-388Adverse effect, 2, 228-231, 260, 293-295, 640Aerosol, 79, 84-86, 170, 185, 640Aetiology, 640AFNOR test, 640Age

class, 306-308, 640composition, 306-308, 640distribution, 306-308, 640

Age-specific fecundity, 304-308, 640

Age-specific mortality, 304-308, 640Aggregation error, 640Agonist, 640Air

models, 80, 166-171, 187-189pollution, 7, 74, 83, 284, 287tranformations in, 119-121, 403-404

ALARA principle, 6, 262, 640Algicidal, 640Algicide, 640Algistatic, 640Alkalinity, 640, 493Alkylating agent, 640Allergy, 254, 640Allometric relationship, 95Allometry, 640Ambient concentration, 335, 640Ames assay, 246-247Anabolism, 640Anadromy, 640Analysis of variance, 293-294, 641Aneuploidy, 245-247, 641Animal welfare, 228, 239, 468-469, 482-483, 624Anion exchange capacity, 330 ANOVA, see analysis of varianceAnoxia, 641Antagonism, 271, 333Antagonist, 641Antibody, 641Antigen, 497, 641APHA, 641Application factor, 342, 641Artificial soil, 321-324Artisol test, 641Assessment

factors, 266-270, 338, 641of PBTs and vPvBs, 345, 534, 576-577

Assimilation, 122ASTER, 449ASTM, 297, 641Asymptotic threshold concentration, 641Atmospheric

deposition, 74, 83-86, 109-110fall-out, 286-287ozone, 117-118, 284, 403risks, 284-285

INDEX

673

Atrophy, 641Aufwuchs, 641Autopsy, 641Axenic, 641Background concentration, 197, 641Bacteria

test methodology for, 121-125, 298-299Bactericide, 641Base pairing, 641Baseline toxicity, 380, 443-445, 641BCF, see Bioconcentration factorBenchmark

dose, 245, 263-264, 295, 641response 264

Beneficial arthropods, 324-325Benthic, 101-105, 312-319, 642Benzene, 37, 124, 139-140Benzo[a]pyrene, 37, 143, 146Bioaccumulation, 90-114, 196, 291, 346, 391-397, 642Bioaccumulation factor, 90, 642Bioactivation, 135, 642Bioassay, 247-251, 301, 642Bioavailability, 73, 126, 147-152, 232-234, 393-394, 642Biochemical mechanism, 642Biochemical oxygen demand, 642Biocide, 642Biocommunity, 642Bioconcentration,

definition of, 90, 391-392, 642experimental measurement, 96, 392estimation, 380, 391-397factor, 90, 392, 642kinetics, 90-96models, 90-96, 394-397

BIODEG, 409-410Biodegradation

aerobic, 122-126, 409-412, 642anaerobic, 124-126estimation, 409-412experimental measurement, 129-133, 409kinetics, 127, 130primary, 121, 129, 663ultimate, 121, 671

Biodiversity, see Taxonomic diversity, 282-285, 327Biokinetics, 229-231, 257, 642Biological

diversity, 1, 285half-life, 94, 128, 942ligand model, 331-332monitoring, 216, 642oxygen demand, 409, 642

674

Biomagnification, 90-114, 341-343, 642Biomagnification factor, 91, 102, 343, 642Biomarker, 643Biomonitoring, 10, 643Biosphere, 121, 281-284, 643Biota-to-sediment accumulation factor, 643Biotic indices, 643Biotransfer, 181, 196Biotransformation

acetyl conjugation, 138experimental measurement, 141-143glucuronic acid conjugation, 138glutathione conjugation, 136-139, 146hydrolysis, 136-137, 141kinetics, 141oxidation, 117-146, 136, 234phase-I reaction, 136-137, 234, 643phase-II reaction, 137-139, 234, 643reduction, 117-146, 137, 234sulphate conjugation, 138, 234

Bioturbation, 90, 314, 643Birds

test methodology for, 319-322, 324-327effects in, 325-327, 341-343

Blok test, 643BOD, see Biochemical oxygen demandBody burden, 272, 643Box model, 160, 166, 186Bromine, 37Broodstock,643 Cadmium, 112-114Calcinosis, 643Canadian Environmental Protection Act

categorization, 597, 610definitions of toxic and substance, 594domestic substances list, 597existing substances list, 596-598management of existing substances, 610-612management of priority substances, 612new substances, 594-596priority setting, 596-597risk assessment, 596-598

Cancer, 248-249, 435-437, 643Carcinogenesis, 248-249, 435-437, 643Carcinogenicity, 248-249, 435-437, 643Carrying capacity, 304, 643CASE approach, 448Catabolism, 441, 643Catadromy, 643Catalase, 643Cation exchange capacity, 321, 329-330

Index

Concentration-response curve, 293-294Conductivity, 181, 644Conjugation, 136-139, 141, 143, 146, 234Consumer

exposure assessment, 202-212exposure scenarios, 203-206, 602exposure models, 208

Consumption patterns, 205, 288-289Continuous

effect, 264, 644flow, 645

Control limit, 645 Corrosion, 241-242, 483, 493-497, 645Corrosivity, 241, 482, 493Cost-benefit analysis, 8, 26, 516, 645Cost-effectiveness, 8, 33, 468, 470Covalent binding, 433, 502, 645Creosote, 37, 48Cytochrome P-450, 124, 136-140, 144-146, 645 Cytogenetics, 645Cytotoxic, 247, 431, 645Daphnia sp.

acute tests, 297 chronic tests, 301-303generation time, 286, 301life-table studies, 301-303surface/volume ratio, 288

Dataavailability, 22, 46-49, 59, 362-364, 513estimation, 50-55, 159-165, 375-504sources, 364-366, 414-415, 440-441, 449-452quality, 216, 238, 364-371

DDT, 121, 144-146, 192, 284, 378De minimus

level, 6risk, 645

Dechlorinated water, 645 Decision-tree approach, 537Deforestation, 1Dehalogenation, 119, 126, 314, 352 Deionized water, 645Delayed effects, 244, 492, 645Demography, 305Denitrification, 299, 645Density dependence, 304, 645Deoxyribonucleic acid, 645Deposition

dry, 45, 84, 109-110, 168-169wet, 45, 85, 109, 168-169

Depuration, 105, 293, 392, 645Derived characteristics, 646

Index 675

CEC, see Cation exchange capacityCell line, 643CEN, 643CERCLA, 643Chelation, 644Chemical categories, 471-475, 483-485, 633Chemical degradation, see Abiotic degradationChemical descriptor, 376, 427Chemical oxygen demand, 409, 644Chemical Substances Control Law (Japan)

data requirements, 582exposure assessment, 577-579existing chemicals, 584-587GHS, 585Japan Challenge Program, 584-585new chemicals, 581risk assessment, 583, 586-587risk management, 577-580voluntary partnerships, 584-585

Chezy coefficient, 174Chironomids

effects on, 318test methodology for, 317-319

Cholinesterase inhibitor, 255, 644Chromosomal aberration, 245-248, 644Chromosome, 245-247, 644Chromosome aberration tests, 247Chronic, 236, 244-248, 300-304, 644Classification

and labelling, 10, 258-261,453, 529-530, 585by modes of toxic action, 442-443, 476-480 criteria, 258-260, 453, 535, 561

Clastogens, 644Clausius-Clapeyron equation, 388-391 Clay, 127, 179, 321, 330-331 Clearance, 232-234, 257, 644Climatic change, 284-285CLOGP, 382, 417, 439, 441Clone, 644Closed system, 40, 292 CO2 production, 128-129, 328, 409Coal, 37, 150, 212-213, 419COD, see Chemical oxygen demandCoefficient of variation, 644 Cohort, 305, 644Combined chemical effects, see Mixture toxicityCometabolism, 122, 127, 157, 409, 644 Community tests, see Multi-species testsCompartment models, 160-161, 173, 235Competent authority, 526, 530, 644 Compliance, 10, 238, 367, 514, 529-531, 575-576

Dermalcorrosion, 241-242, 430, 493-497irritation, 241-242, 430, 493-497toxicity, 228, 259, 320uptake, 320, 439-440

Detergent, 129, 205, 210-211Deterministic analysis, 646Deterministic model, 165, 646Detoxification, 115, 133-138, 143-148Detritus, 102, 105, 173, 646Detrivorous, 646Developmental toxicity, 251-255, 360-361, 438, 498-500 Dieldrin, 38, 184-189, 260-261, 319Dietary uptake, 102, 112, 156, 321Diffuse sources of pollution, 4, 31Diffusion, 74, 86-87, 91-92, 109, 287-288Dilution factor, 171-172Dilution models, 171-172, 176Discriminant analysis, 434, 448, 457Dispersant, 646Dispersion

description of, 82, 167-168, 171-176 coefficient, 82, 167, 173-175models, 82, 167, 172-173

Dissimilation, 172Distilled water, 646Distribution, 646Diversity index, 646DOC, 646DOM, 646Dose, 20, 229, 233, 647Dose-effect curve, 260-266Dose-response assessment, 260-266, 647 Downstream user, 525, 549-550Dumping, 41, 592Dyes, 37-38, 40, 48, 51, 59, 69Earthworms

artificial soil for, 323-324in food chain, 341-343test methodology for, 323-324

EC50, 293-299, 647, 656ECETOC, 647, 656Ecosystem

tests, see Multi-species testsmodels, 282

Ecotoxicogenomics, 335-336Ecotoxicity

aquatic, 290-308, 442bird, 324-327mammalian, 324-327sediment, 313-319

selection criteria for testing, 283terrestial, 319-328

Ecotoxicologydefinition of, 281disciplines of, 281-282

ED50, 647Eddy diffusion, 74, 647Effect

biochemical, 231, 245, 642chronic, 244, 434-435, 644carcinogenic, 248-251, 435-437, 643ecotoxicological, 281-356haematological, 237-238, 245histopathological, 237-238, 245, 652local, 241-244, 430morphological, 229, 237neurological, 231, 659pathological, 237, 246reproductive, 251-253, 438-441, 498-501, 665subacute, 236, 244-246subchronic, 244-246, 295, 608systemic, 232-233, 244

Effects assessmentcomprehensive, 343definition of, 647derivation of PNECs, 337-345for ecosystems, 281-356for micro-organisms, 298-299for predators, 341-343human health, 258-272preliminary, 338refined, 338

EINECS, 513, 647Eisenia fetida, 323-324Elimination

processes, 91-92rate constant, 93-95, 392

ELS tests, 285, 302Elutriate, 648Emission

calculations, 50data availability, 46-59estimation of, 51-55, 61-67factors, 49scenarios, 61-67steps in, 51-55, 61-67estimation tools, 59types of, 43

Emissionsblock, 45continuous, 45

676 Index

diffuse sources of, 7, 45peak, 45point sources, 7, 45

Empirical models, 428, 658Emulsifier, 648End-of-pipe treatment, 46Endocrine, 648Endocrine disruption, 255, 336-337Endpoints, see Toxicological endpointsEnthalpy, 388-390, 648, 651Entropy, 389-390, 399-401, 648, 651Envirogenomics, 335Environmental

fate, 73-152, 375-427impact assessment, 648quality objective, 335, 648quality standard, 648, 667risk analysis, 296, 649stewardship, 553-554, 564-565, 569-570transport, 50, 649

Enzymeactivity, 139-142, 141, 237, 257induction, 121, 137, 141-147, 649inhibition, 142, 145, 649kinetics, 141

EPA (US), see U.S. Environmental Protection AgencyEpibenthic, 314, 319, 649Epidemiology, 239, 649Epifauna, 649Epigenetic changes, 649EPPO, 1, 32, 324, 649Equilibrium, 181-182, 649Equilibrium partitioning, 74-77, 148, 314, 378-397, 649Escherichia coli, 246, 435Expected environmental concentration, 649Estimation methods, Chapters 2-5, 9-11Estimation models

acid dissociation constant, 235aquatic toxicity, 290-308, 442-447, 486-493, 665bioaccumulation, 90-114, 196-201, 391, 453, 642biodegradation, 121-129, 408-412, 441-442, 642chemical degradation, 73, 114-121Henry’s law constant, 79, 382-385, 652human health effects, Chapter 6, 430-442n-octanol-water partition coefficient, 378-381, 660soil sorption, 75-76, 385-388, 667vapour pressure, 388-391, 652water solubility, 397-403

ET50, 649, 657Eukaryotic systems, 247Eukaryote, 246, 649, 663

European Chemicals Agency, 517, 529, 550-551Eutrophication, 649Excretion, 93, 104, 113, 135, 137-139, 649Existing chemicals, 511-513, 553-554, 556-557, 583-

585, 596-597, 630-633Exogenous, 245, 255, 308, 435, 649Expected environmental concentration, 647, 649 Experimental measurement

acid dissociation constant, 235 bioaccumulation, 90-93, 103-109, 111, 113-114, 392biodegradation, 73, 121-133, 175-177, 408-414, 642biotransformation, 73, 133-147, 394-397, 440, 643chemical degradation, 73n-octanol-water partition coefficient, 375-382, 386,

399, 660 soil sorption, 177, 386, 413water solubility, 31, 375-376, 397-403, 555

Exponential growth, 122, 128-129, 298-299, 304-305, 650

Exposure-based waiving, 470-471, 480-481, 484-485, 500

Exposure concentrations, 31, 165, 171, 184, 292, 555Exposure

assessment, 159-226, 285-288, 535-536, 650birds and mammals, 114, 324, 338, 314-343complexity of, 285-290consumer, 61, 196-211, 498, 533-534, 646 dermal, 205, 215-217, 273, 285, 361drinking water, 121-126, 174-177, 196-202, 272-273,

606fish, 198, 289, 341-343food crops, 197-200ingestion, 195-217, 272-273, 314-319, 586, 650inhalation, 195-218, 234-250, 267-273, 320, 535-536meat and milk, 114, 199-200, 202modelling, 67, 159-221, 470, 636,mother's milk, 200multimedia, 4, 668non-linear, 287occupational, 31, 195-221, 363, 576oral, 204, 254, 361-362, 217, 216primary and secondary, 206route, 273, 321, 342, 367-370, 431-438sample calculations, 181, 200, 340surface/volume area and, 288systems, 290-292, 314, 319, 328through food, 197-200, 341-343tiered approaches, 357time, 142, 286-291, 302, 393, 647to mixtures of chemicals, 270, 332

Exposure of man

Index 677

exposure and intake, 195-221exposure via the environment, 196-200occupational exposure, 212-221consumer exposure, 201-212

Exposure scenario, definitions of, 61, 195for consumers, 203-210, 273-274, 361, 372, 469for the workplace, 212-221tentative, 64-68, 537, 584, 650final, 61-68, 527-537annex to SDS, 549

Exposure systemsflow-through, 97, 105, 291-293, 328, 392static, 291-293, 312, 486, 383-386, 667renewal, 291, 293, 667for sediment, 314for soil, 319-322for water, 290-293

Extinction probability, 650 Extrapolation

factors, 356, 650interspecies, 231, 234-235, 251, 255 intraspecies, 234methodologies, 31, 266-270, 337-345models, 165, 266-270, 337-345, 658route to route, 269

Eyecorrosion, 241-242, 430-431, 650irritation, 241-242, 430-431, 650

Factorsabiotic, 287, 326-331, 639 biotic, 287-298, 331modifying toxicity, 281, 328-331

FAO, 255, 650Fate,

processes in soil modelling, 177 continental distribution, 181-189, 284environmental transport, 73-82local distribution, 82, 168, 171regional distribution, 197, 181-187

FATS, see Fish acute toxicity syndromesFDA, 448, 451, 615, 650 Fecundity, 304-305, 308, 640, 650Feeding rate, 101-102, 104, 289Fertilizer, 43, 45, 575Fick’s law, 95, 288Field studies, see Multi-species testsFIFRA, 650First-order

process, 85, 161, 651 reaction, 115, 119, 161-162, 178, 651

First-pass effect, 234, 651Fish

acute tests, 295-300 chronic tests, 300-304early life stages, 302-304elements of a test protocol with, 298acute toxicity syndromes, 442, 462-463, 507

Fitness, 651Fixed dose procedure, 236, 240-244 Flocculation, 651Flow-through, 105, 291-293, 328, 392, 651Foci, 251, 651Foetus (Fetus), 651Foliar uptake, 198Food

additives, 238, 357-362, 441, 517contact materials, 207, 357, 362safety, 107, 477-478

Fragments constants, 376, 381Freundlich isotherm, 651Fugacity, 147-152, 199-200, 398-391, 399, 651Function category, 51Functional tests, 298, 332Fungicide, 312, 329, 350, 651Gametes, 304, 651Gas absorption, 74, 84-86, 88, 152, 182Gastrointestinal, 101-104, 195, 362, 439, 651Gaussian Plume Model, 167-168, 190GEMs, 651Gene, 245-248, 336, 438, 651 Generation time, 50, 284-286, 651Genetic toxicology, 245-251, 651Genome, 255, 272, 336, 450, 651Genomics, 255, 257, 272,335-336, 450, 651Genotoxicity, 245-257, 360-361, 435-437, 477, 651Genotype, 308, 651Gibbs free energy, 74-75, 651Global harmonized system, 259, 534, 585Good laboratory practice (GLP), 238, 630, 651Good modelling practice, 370-371Growth

inhibition, 291-299, 488, 583rate, 128, 295-308test, 302, 323

Half-lifeair, water, sediment and soil, 73-152, 159-189, 412 biodegradation, 172biological, 94, 128, 642compartmental, 412-414definition of, 652hydrolysis, 115-121, 173-178, 404-409

678 Index

Index 679

photolysis, 403tropospheric oxidation, 118

Haploid, 641, 652 Hardness, 298, 330, 652Harm, 209, 477, 553, 611-612, 652Hazard

assessment, 4-5, 228-233, 255-271, 531-540, 631-636

identification, 2-5, 258, 536, 652quotient, 19-24, 270-273, 536-539, 652

Hazardous concentration, HC5, 338-341, 489-493, 652HCp, 652

Heavy metal, 329 Henry’s law constant, 31, 79-88, 175-180, 382-385, 652 Hepatocyte, 257, 652Hepatotoxic, 652Herbicides, 309, 334, 338, 353, 652High production volume chemical, 22, 468-470, 475,

511-515, 559,573, 584-585, 596-597, 630-633 Histology, 652Histopathology, 237, 254-255, 652 Homeostasis, 652 Hormesis, 652HPVC see High production volume chemicalHuman

effects assessment, 227-274 exposure, 195-221, 229-235ranking of effects on, 230

Humic substances, 149, 319, 646Hydra, 340, 653Hydrogen bonding, 380, 384-385 Hydrogen ion concentration, see pHHydrolysis, 73, 115-121, 173-178, 404-413Hydrophilic, 92-95, 233-234, 378, 393-397, 653Hydrophobic(ity)

and accumulation, 380, 394-397and degradation, 186and biotransformation, 133and Kow, 378-379and sediment, 104, 380, 492and soil sorption, 380, 386definition of, 653 parameters, 380

Hydrosphere, 126, 404, 653Hydroxyl radical, 118, 403Hypothesis testing, 293-294, 300Hypoxic, 753IC50, 653ICp, 653ID50, 653

Immune response, 242, 254, 497, 640-644, 653 Immunotoxicology, 254, 653Immunotoxicity, 228, 254, 451, 604Impermeable, 302, 653Incineration, 38-43, 48, 53, 516, 636Incipient LC50, 294, 653, 670Incremental unit risk estimate, 653 Indicator, 217, 231, 270, 376-410, 653Indicator species, 653Individual risk, 7, 270, 654Induction

and biodegradation, 121and biotransformation, 137, 141-147and carcinogenicity, 248-251, 254definition of, 654enzyme, 121, 137, 141, 145-147, 649

Industrial category, 53-55, 68Infauna, 654Inherent biodegradability, 130-131 Initiating event, 654Initiator, 251, 654, 663, Insecticides, 144-145, 296, 325-331, 338, 654Intelligent testing strategies, 467-504Intermedia transport, 73-74, 82, 84, 181-182Intermediate

biotransformation, 139, 146chemical, 39, 55-57

Interspecies variation, 5, 266-267Interstitial water, 102-103, 313-316Interstitial water quality, 316Intramedia transport, 73-74, 80, 82Intraspecies variation, 5, 236Intrinsic rate of increase, 305-306Intrinsic growth rate, 304, 308Invertebrates, 111, 297, 301-302, 317, 319-325In vitro

method, 142, 256-258, 480-484test, 256-258, 470-471, 480-483, 500

In vivotest, 235-256, 290-328, 362-363, 493optimized test, 482-483

IPCS, 195, 229, 365, 591 Iron, 37, 118, 124, 137, 139, 655IRPTC, 637, 654Irritation,241-243, 258-259, 430-431, 493-497Ischaemia, 654ISO, 297, 628, 654ITS, see Intelligent Testing StrategiesJECFA, 365Joint action, 270-271, 332-333, 654 Karyotoxicity, 654

Knowledge pyramid, 28, 371Kow

and accumulation, 95, 100, 392-397, 490-493and biodegradation, 123and ecotoxicity, 381, 443-445, 488-492and sorption, 380, 385-357and water solubility, 399-400estimation of, 381-383experimental measurement, 379general aspects of, 378-383in multimedia models, 182-184

Langmuir adsorption isotherm, 655Larva, 302, 324, 655LC50

definition of, 655 determination of, 295-300estimation of, 295-298, 443-447, 486-493

LD50definition of, 655determination of, 240-242 estimation of, 430-432

Leachate, 43, 327, 386, 655Leaching, 82-83, 177-180, 285, 386Lead (Pb), 330, 563-564Lentic, 351, 655Lesion, 651, 655Lethal, 240-241, 247-248, 293-294, 655Life cycle,

of a chemical, 18, 43, 195-196, 511-512, 521, 535of a species, 285, 290, 300-302

Life history, 350, 662, 665Life-histories, 286, 289Life-table studies, 301-306Ligand, 151, 331-332Limit value, 266-267, 365, 655Linear free energy relationships, 377, 381, 419Linear regression analysis, 199Lipinski's rule of 5, 99-101Lipophilic, 653, 655, 378-382Liver nodule, 655Loading, 291-292LOEC, 293-294, 655LOEL, 655Logistic

distribution, 339growth, 299, 304-308

Logit transformation, 656Lognormal distribution, 338-340, 656Lotic, 312, 656Lotka theory, 304LT50, 654, 656

Lux, 656Lysimeter, 656MAC, see Maximum allowable concentration, 656Macrocosm, 311, 353-357Macrophages, 656, 661Macroscopic (gross) pathology, 656Main category, 56Malignancy, 248, 656Malignant, 656Mammals

accumulation in, 113,341-343accute single dose toxicity, 240biotransformation in, 141carcinogenicity, 248-251chronic studies, 244-245developmental toxicity, 251-253exposure of, 229-235factors for extrapolation, 266-270generation times, 286genotoxicity, 245-251number of species, 282repeated dose toxicity, 244-245reproductive toxicity, 251-254secondary poisoning, 144, 341-343subacute toxicity, 360, 668surface/volume ratio, 288

Manning coefficient, 174Margin of safety, 234, 344, 656 Mass flows, 83, 160-164, 181, 185-189Mass balance calculations, 48, 160-164 Mass balance equation, 77, 111, 160-164, 292Maximum acceptable toxicant concentration (MATC),

249, 656Maximum allowable concentration (MAC), 656Maximum permissible level (MPL), 7, 267Measurement error, 656Median lethal dose, 240, 431, 657Median lethal concentration, 293, 431, 657Median tolerance limit, 657Medulla, 657Meiofauna, 657Mesocosm, 308-312, 328-329, 343-345Mesothelioma, 657Meta-analysis, 237-238, 657Metabolic activation, 35, 257, 435, 440, 442Metabolomics, 255, 336MFO, see mixed function oxydaseMicrobial degradation, 73, 121-133, 408-412Microcosm, 308-312, 328-329, 343-345Micronucleus test, 247-248Microtox, 298, 657

680 Index

Migration of populations, 657Mineralization, 115, 121, 411-412, 658Minerals, 37, 39, 106, 127Minimum significant difference, 658MITI test, 131, 409, 626Mixed function oxydase, 136-137, 657Mixture toxicity

principles of, 270-272, 332-335scales, 332-333

Model ecosystems, 309, 327Model error, 658Models

air, 166-171applications and limitations, 182-184compartment, 161-164consumer exposure, 208data requirements, 165, 176-177, 182dilution, 171-172dispersion, 172-173extrapolation, 7, 257, 266-270, 338-341exposure, 159-189, 208, 215-216, 235human exposure, 195-221long-range transport, 187-189Mackay, 181-189multimedia, 181-189occupational exposure, 214-218PBPK, 96, 199, 234-235purpose of, 160soil, 177-181sophistication, 159-160versus measurement, 165-166water, 171-177

Modifying factors of toxicity, 235-238, 328-331Monitoring, 10-11, 50, 165-166, 215, 579-586Monte Carlo simulation, 212, 659Multigeneration study, 659Multimedia models, 181-189Multimedia uptake, 103, 196-202Multiple exposure, 6, 195Multiple-compartment models, 96Multi-species tests, 308, 310-312, 327Multivariate techniques, 309, 446Mutagenesis, 245-248, 278, 459Mutagenicity, 245-248, 360-363, 435-437Narcosis, 443-445, 488-492Necropsy, 245, 659Necrosis, 145, 323, 659Negligible risk level, 7Nematocide, 659Neonate, 659Neoplasm, 276, 313, 659

Nephrotoxicity, 659Neurotoxicity, 144, 254-255, 360, 563New substances, 511, 513, 557, 581, 594New chemicals, 511, 513, 557, 581, 594Niche partitioning, 286NIMBY principle, 659Nitrification, 122-123, 299, 360Non-target organisms, 51, 361, 660No observed adverse effect level (NOAEL), 260-262,

659-660No observed effect concentration (NOEC), 294, 659-660Non-phase-in substance, 524, 529,550Normal distribution, 339, 660NOx, 38Occupational hygiene, 226, 660Octanol-water partition coefficient, 378-382, 660Ocular, 241, 482, 660OECD, see Organization for Economic Co-operation

and DevelopmentOligotrophic, 660Oncogene, 660One-hit model, 660Organelle, 660Organic carbon content, 76, 315-316, 385-387Organic matter, 76, 177-179, 314-316, 386-388Organization for Economic Co-operation and

Developmentbiocides, 637biotechnology, 637chemical accidents, 637Chemicals Committee, 628Council, 628endocrine disrupters, 630Environmental Policy Committee, 628hazard assessment, 631pesticides, 637existing chemicals, 630-636GLP, 630guidelines for testing, 624-630harmonisation, 630HPV chemicals programme, 630-633MAD, 624new chemicals, 636novel foods, 637risk management, 636SIDS, 631

Organophosphorus compounds, 144-145Oxidation, 117-118, 122-126, 136-137Paracelsus, 227Parameter uncertainty, 660Parthenogenesis, 660

Index 681

Partial least square analysis, 662Partition coefficient,

air-water, 383octanol-water, 378, 443, 492, 660-661sediment-water, 89soil-water, 75-79, 385-388

PBPK, see Physiology-based pharmacokinetic modelsPBT, see assessment of PBTsPCA, 661PCB, 102, 144, 201-203, 287PCP, 151, 340PEC, see Predicted environmental concentrationPerceived risk, 661Percentiles, 661Perfluorinated acids, 561Permissible exposure limit, 661Peroxisome, 661Persistence, 345-346, 661Pesticide, 661Pesticide residues, 360PESTLA model, 178-179Petrol, 37pH, 661Phagocytosis, 661Pharmacodynamics, 661Pharmacokinetics, 661Phase-I reactions, 136, 662Phase-II reactions, 137, 662Phase-in substance, 520, 523-524, 548, 549, 662Phenology, 662Phenotype, 662Photobacterium phosphoreum, 657Photochemical degradation, 119, 121, 662Photochemicals, 51, 57-59Photodegradation, 662Photolysis, 120-121Photoperiod, 662Physicochemical properties, 375Physiology-based pharmacokinetic models, 235Phytotoxicity, 297, 323Plants

aquatic, 297-298terrestial, 106test methodology for, 297-298, 322-323 uptake in, 106

Plastics, 37, 51, 67-69PLS, see Partial least square analysis, 662PMN, see Premanufacture notification, 662PNEC, see Predicted no effect concentration, 662PNEL, see Predicted no effect levelPoint-source pollution, 4

Polybrominated diphenyl ethers, 562-563Polychlorinated biphenyls, see PCBPopulation

biomass, 663dynamics, 304growth rate, 304

Population growtheffects on, 304exponential, 305logistic, 306

Pore water, 663Porous pot test, 663Potentiation, 663Power of a test, 663Precautionary principle, 663Precipitation, 663Predicted environmental concentration, 4-5, 22-24, 182,

537, 661Predicted no effect concentration, 5, 182, 663Predicted no effect level, 663Predictive risk assessment, 663Preliminary test, 663Premanufacture notification, 592Primary biodegradation, 408, 663Primary degradation, 411Principal component analysis, 661Priority substances, 168, 513-514, 612Probit/log transforms, 663Probits, 663Production processes, 53Promoter, 663Proportional diluter, 292Protein binding, 663Proteomics, 664Proto-oncogenes, 248Public health impact assessment, 664Pulmonary alveoli, 664Pyrethroids, 145-146QSARs, see Quantitative structure-activity relationshipsQSPRs, see Quantitative structure-property relationshipsQuality

assurance, 8, 664control, 8, 664criteria, 8, 664guidelines, 8, 664objectives, 8, 664standards, 8, 664

Quantal effect, 664(Quantitative) structure-activity relationships

computer programmes, 486databases of, 440

682 Index

modes of toxic action, 281-442-443prediction of human health endpoints, 430-431regulatory application of, 467, 473, 476validation of, 427, 429, 634

Quantitative structure-property relationships, 389, 664Quantum-chemical parameters, 664Quotient method, 664Range-finding test, 664REACH

European Chemicals Agency, 529, 550-551authorization, 526-527development of, 511-516chemical safety assessment, 512, 517-526, 531-541chemical safety report, 531-541data sharing, 524downstream user, 520, 525evaluation, 525-526enforcement, 530-531exposure scenario document, 61-68, 521-522, 535-

536non-phase-in substance, 523-24phase-in substance, 520, 523-524, 662protection goals, 537registration, 517-524restriction, 527-528reversal of the burden of proof, 513, 515safety data sheet, 541-542structure of the legislation, 516-519use and exposure category, 533

Reactive chemicals, 443, 445-447, 478Read-across, 471-475Ready biodegradation, 175Receiving water, 172, 664Receptor, 146, 228-229, 331-332Recommended limit, 664Reconstituted water, 665Redox potential (Eh), 329Reduction, 137Reductive dehalogenation, 119,126Reference

compound, 665environment, 665site, 665

Regression analysis, 448, 665Regression coefficient, 665Relative risk ranking, 5, 28Remediation, 665Renal, 665Replicate, 665Reproducibility, 665Reproductive toxicity, 251-253, 258, 438, 498-500, 665

Resistance time, 665Response

continuous, 265, 665graded, 663

Resuspension, 74, 82, 88-89Retrospective risk assessment, 665Rhizosphere, 319, 665Risk

cumulative, 7individual, 7perceived, 666

Risk assessmentdata requirements, 166, 176-177, 180-183, 357-361data gaps in, 21-23, 362-364, 513decisionist model, 15definition of, 2, 22, 665integration in, 11, 17-18policy, 14-17role of science in, 15-17site-specific, 281, 319, 322technocratic model, 15transparent model, 16

Risk characterizationdefinition of, 2, 666environment, 23-24, 345-346, 536-538human health, 272-274, 536-538sample calculations, 200, 340

Risk classification, 666Risk communication, 12, 15, 666Risk evaluation, 666

environment, 23-24, 345-346, 536-538human health, 272-274, 536-538

Risk limits, 6-7, 33, 348Risk management, 1-19, 511-516, 666Risk management measures, 46, 62-63, 537, 666Risk perception, 666Risk prediction, 228, 272Risk quotient, 24, 666Risk reduction

definition of, 2, 666types of measures, 8-11, 46

Risk-benefit analysis, 6, 8, 666Rodenticide, 666Root

concentration factor, 106-109growth test, 323uptake, 107, 109

Round-robin test, 666Run-off, 666Safe concentration, 666Safety data sheet 67, 541-543

Index 683

Safety factor, 666Salinity, 287, 667Salmonella thyphimurium, 246SAM, 667SAR, see (quantitative) structure-activity relationshipSandoz calamity, 1SARA, 667Satellite groups, 667SCAS test, 667Screening

test, 130-132, 409-410, 667Secondary poisoning, 200, 206, 341, 667Sediment

burial, 82, 173, 189deposition, 76, 102quality triad, 315

Sediment toxicity testsexposure systems, 314goals of, 313test methodology for, 314-319 test species used, 317

Sediment-water exchange, 88, 175, 314Sedimentation, 74, 82-84, 88-89, 182Semi-static, 291-292, 667Sensitization, 242-244, 432-434, 667Sewage treatment plant, 66, 175-176Shear stress velocity, 174Silent Spring, 511, 544SIMPLEBOX, 152, 181, 184-187, 192SIMPLETREAT, 69, 175-176Simplicity-complexity dilemma, 29Sister chromatic exchange, 247Site-specific risk assessment, 150, 281, 319, 322Skin sensitization, 242, 497Slow-stirring method, 379SMILES, 449, 451Soil

artificial, 321-324leaching, 40, 82-83, 177-182models, 160, 165, 177-181organisms, 22, 177, 288, 319run-off, 88sorption, 177, 386, 413toxicity tests, 322

Solids-water partition coefficient, 76, 111, 131, 175, 315Sorption

experimental measurement, 386estimation of, 386-388, 417

Source characteristics, 169Source term, 201, 204, 667Spatial scales, 50-51, 168, 181-182, 284

Spawning, 667Speciation, 95-97, 148-151, 329-331, 667Species

aquatic, 338-339sensitivity of, 34, 338-339terrestrial, 31

Specifically acting chemicals, 442-443, 478Spiked sediment toxicity, 316Stable age distribution, 304, 307, 667Stakeholder participation, 2, 11-12, 15, 18, 515Standards, 667Static test, 667Static renewal test, 667Statistically significant effects, 667Statistical analysis, 236-237, 301Steady-state, 28, 90-92, 105-106, 175-182, 392-394, 668Steady-state concentrations, 92, 105-106, 175, 182, 394Stochastic

analysis, 668model, 668

Stochasticity, 22, 668Stock solution, 668Stoichiometry, 125, 410, 668STP, 43, 48-59, 69, 668Stress, 668Structural parameters, 309Structural classes, 442, 477-478, 488Sturm test, 129, 668Stygobiont, 668Stygophile, 668Subacute, 228, 244, 268, 360-362, 668Subchronic, 229-230, 360-362, 668Sublethal, 293-295, 668Surface/volume area, 228Surfactant, 129-130, 669Surveillance, 10, 215, 218, 221, 236, 669Survival time, 669Susceptibility, 258, 267, 270-271, 669Synergism, 271, 669Systemic effects, 233Taxonomic diversity, 282-2832,4,5-T, 382,3,7,8-TCDD, 38, 126, 146t1/2, see Half-lifeTDI, see Total daily intakeTEF, see Toxicity equivalency factorTemporal scales, 80, 284-285Teratogen, 669Teratogenesis, 669Terrestial toxicity

exposure systems for, 319-322

684 Index

test methodology for, 322-328Test guidelines, see OECD Theoretical models, 427, 475Threshold levels, 19, 20Threshold limit value, 669Threshold-effect concentration, 669Threshold of toxicological concern, 449, 476-480Time scales, 50, 284-285, 435, 536-537Time weighted average concentration, 669Time-independent test, 669TLV, 670TOC, 670Tolerance, 113, 144, 322, 352-353, 670Topical, 321-322, 432, 497, 670TOPKAT, 430-435, 447-448, 459, 474Topological indices, 376-377, 493, 448Total body residue, 492Total daily intake, 200, 272, 525Total hydroxyl reaction rate constant, 404Toxicity equivalency factors, 670Toxic Substances Control Act (USA)

category approach, 560exposure assessment, 555-557existing chemicals, 558-564HPV Challenge Program, 559new chemicals, 557(Q)SARs, 554-555risk assessment, 556risk management, 553-554voluntary partnerships, 570

Toxic unit, 333, 670Toxicity range factors, 488Toxicity

acute, 240-241, 430 acute single dose, 236, 240-241, 326chronic, 251-255, 434-435curve, 260-265, 294developmental, 251-253, 360-361, 498-500general aspects, 228-229identification evaluation, 352, 670 in vitro, 257in vivo, 257, 431long-term, 31, 300mammalian, 324, 327, 346, 431, 582-584microbial, 299mixtures, 281, 332-355modifying factors of, 328prenatal, 251-254 repeated dose, 236, 360-362reproductive, 251-253, 438sediment, 281, 313-319

short-term, 295-297strategies for testing of, 315, Chapter 11 subacute, 360 subchronic, 342, 583terrestrial, 319-322time curves, 236, 294-295

Toxicodynamics, 245, 267, 272, 428, 670Toxicogenomics, 254-255, 278, 355Toxicokinetics, 228-229Toxicological endpoints, 283, 497-498Toxicology

definition of, 227-228“protocol”, 228regulatory, Chapters 12-16

Toxiguard, 670Toxin, 670Transcriptomics, 255, 257, 336, 670Transformations

logit, 656probit, 663

Translocation, 155-156, 201, 248Transport

advective, 74, 80, 84, 88diffusive, 88-89, 186, 199intermedia, 73-74, 82, 84, 181-182intramedia, 73-74, 80, 82

TSCA, see Toxic Substances Control Act TTC see Threshold of toxicological concern Tumour, 237, 248-251, 262-263Turbidity, 671Two-compartment model, 92, 96Ultimate biodegradation, 121, 125, 410-412Ultimate degradation, 125-126, 412Ultimate median tolerance limit, 671UN, 588-589, 671Unacceptable effects, 3, 283UNCED, 1, 3, 512, 545, 671Uncertainty

analysis, 170, 197, 239, 272, 516, 540communicating, 540definition of, 671in extrapolation, 337in models, 22, 374in risk assessment, 21-22in safety evaluation, 540quantification of,23-24types of, 22

Uncertainty factor, 671Upstream water, 671Uptake

by roots, 155

Index 685

foliar, 198from air, 201from food, 101-104, 114from sediment, 102, 104, 314from soil, 106-107, 111, 198from water, 102-105, 392rate constant, 92-96, 101-103, 392, 671

Usein closed systems, 51non-dispersive, 51resulting in inclusion into or onto a matrix, 51wide dispersive, 51, 527

Use and exposure category, 671U.S. Environmental Protection Agency,

environmental stewardship, 553-554, 564-565, 569-570

gatekeeper/guardian role, 564HPV challenge program, 559-560implementation of TSCA, 557sustainable futures, 567voluntary partnership, 569

USES, 60, 671Validation

of models, 155, 156of extrapolation, 337QSARs, 428-430, 633-636

Van Der Waals interactions, 388, 671Vapour pressure, 55-56, 79-80, 171, 176Variability, 21-25, 440VOCs, 38Volatilization, 74, 84-88, 109, 110Voluntary risks, 21vPvB, see assessment of PBTs and vPvBWaste

application, 42incineration, 38, 48treatment, 40-43, 54-55water, 40, 45, 53-54, 65, 129-130, 671

Waste water treatment plant, 130, 175Water

hardness, 330models, 80-81, 171, 173, 175-178solubility, 397-403uptake from, 102-105, 392

Weight composition, 671Wet deposition, 83, 85, 109, 169, 182, 198WHO, 1, 6, 12, 25, 29-30, 671Xenobiotic, 671Xenobiotic metabolism, 279, 440-441, 461, 671Zahn-Wellens test, 130,626, 672Zinc, 27, 35-38, 329-330, 353-354

686 Index