pesticide residues in the total environ- ment:...

PESTICIDE RESIDUES IN THE TOTAL ENVIRON-MENT: RELIABLE DETECTION AND DETERMINA-TION, MITIGATION, AND LEGISLATIVE CONTROL

AND SURVEILLANCE PROGRAMMES

FRANCIS A. GUNTHER

Department of Entomology, University of California,Riverside, California, U.S.A.

ABSTRACTDuring the past few years much has been learned about modes of intro-

duction of pesticide chemicals into all niches of the human environment, andtheir nature and distribution in various substrates. There can be no questionthat all widely used pesticides have become broadly dispersed from thepoints of initial pest-control application, yet it is only recently that wide-spread concern over the probable ecological sequelae and more immediateeffects on man and his food supply has arisen. This concern has now beenabundantly justified, for many of our modern pesticide chemicals are long-lived under almost all environmental conditions. Numerous massive effortshave been undertaken, or are being contemplated, in several countrieshopefully to evaluate both qualitatively and quantitatively the probablesignificance of both short and long-term contamination of foods and feeds,soils, waters, aquatic habitats, forests, rangelands, fibre-producing plants,wildlife, rain, snow, air, and people.

Analytical contributions are basic to these efforts, but their value isdirectly proportional to their reliability; either falsely negative or falselypositive residue characterizations and measurements could adverselyinfluence important conclusions and decisions about this global problemand its future mitigation. Many legislative bodies around the world haverecognized or are recognizing the absolute necessity to control both thenature and the amount of pesticide residues in our food and feeds in theinterests of public health. Some of these bodies are also recognizing that theuncontrolled, widespread, and repeated uses of certain pesticide chemicalsso essential to adequate agricultural production and to even partial sup-pression of invertebrate-borne diseases can have consequences on and in theenvironment far more serious than a momentary hazard from excessiveresidues in a particular crop or crop product.

INTRODUCTIONAs even the most unobservant child quickly learns from direct, unpleasant,

and unavoidable experience, the entire land surface of the earth is generouslyshared by man with an immense variety of biting and sucking insects. As thechild grows older, he learns to his dismay and often to his extreme dis-comfort that most of these flying or crawling pests can also transmit virus

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FRANCIS A. GUNTHER

and other dreadful diseases ranging in severity from mere annoyance tototal incapacitation and often to death (Table 1). Further, he soon learnsthat social and economic status, ethnic background, cultural plateau,adequacy of diet, intellectual level, physical maturity, and even statureof scientific advancement of his culture are of no really significant importance

Table 1. Partial list of insect-borne diseases of man and domestic animals5

Disease Vector Animal qifecieda

African sleeping sickness Tsetse flies ManAnthrax Horse flies All mammalsBubonic plague A rat flea Man, rodentsCattle tick fever Several ticks Cattle, horsesChagas' disease Assassin bugs Man, rodents, dogsDengue Two mosquitoes ManDysenteries Several flies ManEncephalitis Several mosquitoes Man, horses, birdsEndemic typhus Oriental rat flea Man, rodentsEpidemic typhus The human louse ManFilariasis Several mosquitoes ManFowl pox Two mosquitoes Avian speciesFowl spirochetosis A fowl tick Chicken, turkey, gooseLouping illness Castor bean tick Man, sheepMalaria Anopheles mosquitoes Man, birdsNagana Tsetse flies All mammalsOnchocerciasis Several black flies ManPappataci fever A psychodid fly ManPiroplasmosis Several ticks Domestic animalsQ fever Ticks ManRelapsing fevers Several ticks Man, rodents, fowlRocky Mountain spotted fever Two ticks Man, rodentsScrub typhus Chigger mites Man, rodentsSwamp fever Horse flies, deer flies Equine speciesTexas fever A cattle tick CattleTrypanosomiasis Several flies Man, many animalsTularemia Several flies, fleas, lice, ticks Man, rodents, rabbits, ground

birdsVerruga peruana A psychodid fly ManYellow fever Several mosquitoes Man, animals

a Man is susceptible to 23 of the 29 diseases in this partial listing.

to these vicious predators. As his early education progresses, he then learnsthat numerous species of insects also transmit great varieties of diseases toanimals, to birds, and even to plants. From casual but poignant observation,he then learns that the non-aquatic world is also generously inhabited byother insects intrinsically totally destructive to all forms of food, fibre, andwood. Similarly, the unmistakable role of fungi as effective destroyers oflarge shares of man's food, fibre, and wood soon becomes obvious. Lessobvious to our maturing student, perhaps, are the equally serious depreda-tions of the equally omnipresent numerous species of rodents with theirassociated and often deadly parasites; still less obvious are the insidiouseffects on useful plant life of destructive nematodes, for these tiny pestsrequire microscopic examination to be seen. On the other hand, encroachingweeds as unwanted plants are again abundantly but not so forcibly evidentto our observer, probably even if he is a city dweller.

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PESTICIDE RESIDUES IN THE TOTAL ENVIRONMENT

The chronology of man's attempts to coexist with these multitudinousdeterrents to evolving civilization—with its required grouping of both humanand domestic animal populations and concomitant development of intensiveagriculture—surely began with the insects as such unpleasant violators ofboth person and food supply; the rodents probably represented the secondfoe, but as insatiable destroyers of food rather than as conveyors of disease inthese early days of unawareness of bacteria and viruses; the third pest toreceive defensive attention then must have been the fungi as slower butequally formidable destroyers of food supplies and clothing; among thesestages came the inevitable recognition that surely there must be better waysto control unwanted small plants than by laborious pulling by hand or byhoeing.

Thus, man and animals have always been annoyed, made ill, and killedby insects and insect-borne diseases; these effects were usually immediateand obviously serious, and their attempted mitigation has occupied a verylarge part of man's attention for thousands of years, with almost totalreliance upon the physical destruction of those annoying insects large enoughto be seen and apprehended until the prehistoric discovery of the insect-repellent properties of smoke. The insecticidal properties of burning sulphurwere apparently discovered early in historical times, for Homer in TheOdyssey (circa 750 B.c.) mentions the fumigant action of burning sulphur, andPliny the Elder (circa 60 A.D.) wrote of "pest-averting sulphur"; Pliny alsorecommended arsenic to kill insect pests. In addition to their nuisance anddisease-causing values, it has also long been recognized with abundantlyjustifiable alarm that insects, rodents, and fungi pose serious and very directthreats to man's food supply, and thus to his continuing existence in evenelementary states of congregation. There can be no question that the socialanthropological evolution of man through band, clan, tribe, chiefdom, stateand present-day international community, has been seriously and some-times undoubtedly disastrously retarded by these pests, for even today--with our modern arsenal of effective agricultural pest-control chemicals—losses attributable to pests amount to at least one-third of the world foodproduction. For example, it has been estimated5 that worldwide losses inagricultural production from insects alone amount annually today to atleast nine dollars per arable acre, or about 21 billion dollars for the world's2,287 million acres under cultivation, despite modern pest-control measures.

Contrariwise, the larger insects have often been important portions of thediet of man from prehistorical times to the present; many primitive cultureshave relied upon beetles, locusts, caterpillars and other larvae, ants, bees,and other insects as major items of the normal food supply. Their nutritivevalue cannot be questioned, for in general insects are excellent sources offats, proteins, roughage, and especially the B-complex vitamins.

In the agricultural sense, then, cpests are any animals or plants detri-mental to man's food production, storage, and transport. There are severalways to kill or otherwise minimize ravages from pests, but the mostgenerally and immediately effective measure is through the intelligentand guided use of pesticides, those carefully selected chemicals designed tokill pests without—at the same time—presenting undue hazard in agri-cultural use to man and his domestic animals, to any useful widlife, and to

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FRANCIS A. GUNTHER

beneficial soil microorganisms. Some pesticide chemicals may persist foryears in the total environment, and their indiscriminate use on the same areaover long periods can have pronounced but local detrimental effects onsubsequent crops, on water supplies, on wildlife and on aquatic and soilorganisms.

Chemical pest-control agents have been used by man in his agriculturalendeavours ever since he began actively resenting the inroads made by thesediverse pests on his crops and stored products. Thus, the extensive use ofvinegars to preserve many foods, of honey to preserve cooked fruits, of smokingto preserve fish and meats, and of numerous evil-smelling concoctions torepel plant-feeding and animal-biting insects and rodents and to suppressmoulds date from antiquity. Sulphur, burning sulphur (sulphur dioxide),and phenols and acids in smoke were probably the first strictly pesticidechemicals, undoubtedly dating back many thousands of years. Arsenic(probably as the oxides) as both insecticide and herbicide was known toPliny the Elder, as mentioned earlier, and the Chinese used an arsenicsuiphide in the late sixteenth century7. Other inorganic pesticides subse-quently used included salts of antimony, arsenic, boron, copper, fluorine,lead, manganese, mercury, selenium, sulphur (various oxidation states),thallium, and zinc. Most of these chemicals affected chewing animal pestsonly, but a few of them were effective herbicides. Insecticides that killedinsects by contact date back into Chinese history with use of the wilforinealkaloids from crushed Thundergod vine, followed in several parts of theworld by the discovery that some of the botanical fish poisons (e.g., therotenoids) were also effective insecticides against some species. The use ofnicotine-type compounds dates back about 300 years, when crude tobaccopreparations were used in France; other botanicals included paipa roots(China), the pyrethrins (East and South Africa, Brazil, India), thePeruvian ground cherry (China, Europe, South America), camphor(probably originally from Asia), turpentine (Asia, Europe, the Americas),ryanodine (South America), the veratrine alkaloids (the Americas), andothers8.

The so-called modern synthetic organic pesticide chemicals for agricul-tural use have been developed since about 1935. Their remarkable andprompt acceptance around the world stems from their long-lasting effective-ness at low dosages, as contrasted with the inorganic pesticides, and from thefact that they were essential and timely in helping provide food for a worldpopulation that now doubles every 40 years. At present there are nearly1,000 different pesticide chemicals in use around the world, but only about250 are major pesticides in agricultural production, including nearly 100insecticides and acaricides, about 50 herbicides, about 50 fungicides, about20 nematocides, about 10 rodenticides, and about 20 defoliants, plantgrowth regulators, desiccants, and others. Very substantial amounts ofthe leading 12 insecticides, 12 fungicides, and 7 herbicides are used aroundthe world wherever modern agriculture is practised11. The annually in-creasing sales (domestic and export) of pesticide chemicals in the UnitedStates are shown graphically in Figure j9, 11; similar increases must exist forall other countries producing these chemicals for agricultural appli-cations.

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1000

900

800 -

,./700- ao —.a.600- ao50O- a'o

: I1954 1956 1958 1960 1962 1964 1966 1968

Years

Figure 1. Combined domestic and export sales of pesticide chemicals in the United States;dashed line extrapolated9. 11

PERSISTING PESTICIDE RESIDUESMost of the pesticides applied directly to plants before about 1940 were

inorganic; their deposists on plant parts remained on the plant surfacesand could largely be removed by commercial washing, as with dilutehydrochloric acid or sodium silicate solutions for the calcium and leadarsenates. By about 1950, however, it was broadly realized that the modern,synthetic, contact, organic insecticides generally possessed a potentiallyserious disadvantage in terms of the public health. Their deposits couldpenetrate treated plant parts and remain as internal residues, often forlong periods. These residues were sometimes altered by the plant cellularenvironment into various products, often of unknown toxicology, as illus-trated in Table 2. The systemic pesticides, deliberately designed to penetraterapidly throughout treated plant and animal tissues, were also soon found toform various metabolites and other alteration products, sometimes in suchextremely small amounts as to present a truly exciting challenge to theanalyst. Pesticide chemicals admixed with soils can also be degraded orotherwise altered by both the soil environment itself and the microorganismspresent and may therefore be of concern.

The few residue analytical chemists then available to work in this areasoon realized the seriousness of these slowly unfolding problems associatedwith pesticide residues in foodstuffs, for there could be no question that themaintenance of modern agricultural production requires extensive andcontinuing use of these and many other agricultural chemicals. Shortlythese few residue chemists began informally to organize their efforts and toexchange experiences and ideas at scientific meetings; there were no text-books or analytical manuals for this new area in 1950, and the only publica-tion outlets were the analytical journals and the several journals of thebiological disciplines involved. Clearly, in a field where the analyticalrequirements became almost daily more fastidious, specific publicationoutlets were essential for maximum effective communication; in thisatmosphere of urgency, I concieved the Journal of Agricultural and Food

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FRANCIS A. GUNTHER

Table 2. Illustrative metabolic and other alteration products associated with aged pesticideresidues within plant and animal tissues and soils (from the general literature)

Major metabolicPesticide Substrate and other products

Aidrin Animal, plant, soil Dieldrin and othersAmiben Soybeans Amiben N-glycosideAmitrole Plants, soils SeveralBHC (lindane) Animals, plants, soils Pentachlorocyclohexene,

trichlorobenzenesBidrin Animals, plants, soils Series of compoundsCaptan Plants ThiophosgeneCarbaryl Animals, plants Alpha-NaphtholColep Plants Colep oxonCoral Animals Coral oxonDDT Animals, plants, soils DDE and othersDemeton Animals, plants Sulphoxide, sulphoneDiazinon Animals DiazoxonDibrom Animals DDVP and othersDichiobenil Plants 2,6-Dichlorobenzoic acidDimethoate Animals, plants, soils Dimethoxon and othersDi-Syston Animals, plants Sulphoxide, sulphone, and othersEndosulfan Plants Sulphate and othersFenthion Animals, plants Sulphoxide, sulphoneHeptachlor Animals, plants, soils Heptachior epoxideMalathion Animals, plants, soils Malaoxon and othersMethyl bromide Plants (wheat) N-Methylated proteinsNicotine Animals, plants Cotinine and othersParathion Animals, plants Paraoxon and othersPhosphamidon Plants Desethyl compound and othersSchradan Animals, plants N-oxide and othersSimazine Plants, soils HydroxysimazineThimet Animals, plants, soils Sulphoxide and suiphoneTrithion Plants Sulphoxide and suiphoneZectran Animals, plants Several

Chemistry in 1950 and sponsored by the American Chemical Society in 1952.Prior to this time, centres around the world for the chemical investigationsof pesticide residues in foodstuffs existed at a few United States state ex-periment stations, and the U.S. Department of Agriculture research centres,as listed in Table 3. By 1950, additional residue research was being conductedby the U.S. Food and Drug Administration laboratories, the agriculturalresearch centres of perhaps six major chemical companies around the worldand a few segments of the food industry; these early efforts were almostexclusively centred around insecticides because the persisting residue prob-lem was first recognized in our laboratories with insecticides. Now it is amajor issue in every advanced country.

The enthusiastic acceptance by agriculture of modern organic pesticides,plus their escalating importance in the world economy, is attested by therate at which books on their chemistry and on their residues have appeared.Only one of these books had been published prior to 1940; four appearedbetween 1940 and 1950; 16 appeared between 1950 and 1960; and 62have been published since 1960, (including to date the 29 volumes ofResidue Reviews and the seven volumes of Advances in Pest Control Research).These books are listed3 in Table 4; eight countries are represented by theauthors or sponsors. In toto, these books and the many other technical

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Table 3. Pesticidea residue research laboratories in the United States prior to about 1940

FrearWest and CampbellDeOngAmerican Chemical

\'Vest et al.1955 Frear

Gunther and BlinnHolmesMetcalfRose

1956 HorsfallPerkow

1957 Internati. CommissionIssd. Agr.,Permanent Internati.Bur. Anal. Chem.

1957 Metcalf, ed

Zbirovsky and Myska195.8 Souci1959 Internati. Union of

Pure and Appi. Chem.

Rosival, Vrbousky,and Selecky

1960 Dormal and ThomasGunther and Jeppson

United StatesEnglandUnited StatesUnited States

CanadaCanada

EnglandUnited StatesUnited StatesEnglandUnited StatesEnglandUnited StatesGermanyItaly

United States

CzechoslovakiaGermanyGermany

Organization Location Residue chemist

Cornell University Ithaca, N.Y. L. B. NortonOregon State College Corvallis, Ore. R. H. RobinsonPennsylvania State College State College, Pa. D. E. H. FrearState of California, Sacramento, Calif. Alvin Cox

Bureau of ChemistryUniversity of California

Citrus Experiment Station Riverside, Calif. F. A. GuntherBerkeley Berkeley, Calif. W. M. Hoskins

U.S. Department of AgricultureFruit Insect Investigations Moorestown, N.J. R. D. Chishoim

Vicennes, md. J. E. FaheyYakima, Wash. C. C. Cassil

Agricultural Research Centre Beltsville, Md. F!. L. HallerWashington State College Pullman, Wash. J. L. St. John

a Pesticides involved were anabasine, arsenic, cryolite, the DN compounds, lead, nicotine, petroleum oils,rotenone, sulphur, and tartar emetic.

Table 4. Published books containing pesticide residue information[updated from Gunther (1966)3]

Yearpublished Author Country Title

1939

1942194619481949

Shephard United States The Chemistry and Toxicology of

Society1951 Brown1952 Martin

InsecticidesChemistry of Insecticides and FungicidesDD T, The Synthetic InsecticideChemistry and Uses qf InsecticidesAgricultural Control Chemicals

Insect Control by ChemicalsGuide to the Chemicals Used in CropProtectionChemical Control of InsectsChemistry of the PesticidesAnalysis of Insecticides and AcaricidesPractical Plant ProtectionOrganic InsecticidesCrop ProtectionPrinciples of Fungicidal ActionDie InsektizideLes Substances Etrangeres dons leAliments

Czechoslovakia

Advances in Pest Control Research(book series to date)Insecticides, Fungicides, RodenticidesFremdstoffe in LebensmittelnLebensmittel-Zusatzstoffe andRückstãnde von &hadlings-bek/impfungsmitteln in LebensmittelnToxicology and Pharmacobiodynamicsof Organophosphorus Compounds

Belgium Repertoire Toxicologique des PesticidesUnited States Modern Insecticides and World Food

ProductionTable 4. continued on page 362

361

FRANCIS A. GUNTHER

Table 4—continued from page 361

Yearpublished Author Country Title

1960 LonggoodO'BrienUSDA

1961 Butz and Noebels, eds.

Crafts

HeathSchuphan

1962 Ayres et al, eds.CarsonGunther, ed.

1963 FDAZweig, ed.

Maier-BodeMcMillenPublic Health Service

AOAC

EnvironmentalPollution Panel,President's SilenceAdvisory Committee

1966 NatI. Acad. SciencesCrosby, ed.Whitten

1967 Weed Society ofAmerica

1968 MelnikovBailey and Swift

1969 HassallKearney and KaufmanTorgeson, ed.

The Poisons in Your FoodToxic Phosphorus EstersThe Nature and Fate of ChemicalsApplied to Soils, Plants, and AnimalsInstrumental Methods for the Analysisof Food AdditivesThe Chemistry and Mode of Action ofHerbicidesOrganophosphorus PoisonsZur Qualitat der NahrungspfianzenChemical and Biological Hazards in FoodSilent SpringResidue Reviews (book series to date)Pesticide Analytical ManualAnalytical Methods for Pesticides,Plant Growth Regulators, and FoodAdditivesPfianzenschutz- undSchddlingsbekampfungsmittelClinical Handbook on Economic PoisonsPesticides and the Living LandscapeResearch in PesticidesThe Analysis of Pesticides, Herbicides andRelated Compounds Using the ElectronAffinity DetectorPfianzenschutzmittel-RückstandeBugs or PeopleGuide to the Analysis of PesticideResiduesOfficial Methods of Analysis of theAssociation of Official AgricultureChemists (every 5 years)

United States Restoring the Quality of OurEnvironment

publications on pesticide residue matters are reassuring evidence for every-one everywhere that the world's food supply in its entirety will soon beunder competent and alert surveillance to prevent abuses involving excessivepesticide residues; some countries are already in excellent command of thissituation as will be shown later, and most major crops are under at leasttoken 'market-control' scrutiny. Some of these books raised questions towhich there were no answers at the time. Subsequent books and othertechnical publications have provided answers for most of the earlier questionsabout pesticide residues and their effects, and have abundantly demonstratedat the technical level that properly involved government agencies, the

362

United StatesUnited StatesUnited States

United States

United States

EnglandGermanyUnited StatesUnited StatesUnited StatesUnited StatesUnited States

Klimmer

Hayes1964 Rudd1965 Chichester, ed.

Gudzinowicz

Germany

United StatesUnited StatesUnited StatesUnited States

GermanyUnited StatesUnited States

United States

United StatesUnited StatesUnited StatesUnited States

U.S.S.R.United StatesUnited StatesUnited StatesUnited States

Scientific Aspects of Pest ControlNatural Pest Control AgentsThat We May LiveHerbicide Handbook of the WeedSociety of America

Chemistry of PesticidesPesticide Information and Safety ManualWorld Crop Protection, vol. IIDegradation of HerbicidesFungicides: An Advanced Treatise


world wide agricultural chemicals industry, the organized food industriesstate experimental stations and similar non-profitmaking research institutionshave long been aware of the many problems associated with pesticide residuesin the total environment and that solutions are being systematically found.These research efforts require time, money, and effective manpower, but itis important to realize that the research priorities involved in both theseshort- and long-term investigations of the consequences and of the amel-ioration of pesticide chemical behaviour in the environment should be agreedupon by experts representing public health, chemistry, biochemistry,toxicology, pharmacology, ecology, and internal medicine.

Uninformed individuals everywhere, who are deeply and vociferouslyconcerned that man is callously poisoning his entire world with insidiouschemicals, must be reassured that this eventuality was recognized long agowithin the chemical and associated industries, in agriculture, in the home, inthe cosmetics industry, in the food preservation industry, and in many otherareas, as illustrated in Table 5. Most of these instances were recognized aslocalized problems, and were rectified as promptly as possible when thehazard was realized, usually through legislation acknowledging the rightsof the individual to employment, to nourishment, and to an environment asfree from chemical hazard as realistically achievable in our present society.The history of man has been that he promptly adopts a new means of

Table 5. Some early instances of concern over the direct poisoning of man by advancingcivilization

Approximatedate Effect Gausative agent Source of agent

B.C.

1775177518801890

Cancer

Scrotal cancerCardiac stimulantSilicosisAbortions

Polynuclearhydrocarbons

PolynuclearsDigitalisCrystalline silicaErgot

Smoking of foods

Chimney soot'Dropsy' medicineQuartz miningCereal grain infested with

1900 Heavy metal poisoning Leada, chromium, etc.Glaviseps purpurea

Pottery and pewter cookingutensils

19001910

CancerSelenium poisoning

'Radium' paintsSelenium compounds

Watch and clock dialsThe first systemic

insecticides192019251930

1930

Skin cancerThallium poisoningGoiter, optic nerve

damageBarium poisoning

Ultraviolet radiationThallium acetateDN-compounds

Barium salts

SunlightDepilatory creamWeight-reducing agents

Some cosmetics1930 Nervous Tissue

destructionTriorthocresyl

phosphateJamaica ginger

extract19401940

Liver cancerBladder cancer

Thiourea/3-Naphthylamine

Food preservativeAniline dyes

1950 Kidney poison Lithium chloride Salt substitute1950 Lung cancer Various carcinogens Tobacco smoke19501960

Vitamin E antagonistLiver cancer

p-PhenylenediamineSafrole

Hair dyesRoot beer flavour

1965 Chronic bronchitis Various Smog

a The lead water pipes of the Romans undoubtedly contributed to the usually short lives and decreased fertilityof the wealthy class in the cities.

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FRANCIS A. GUNTHER

securing something desirable, often overlooking possible undesirable side-effects and, also, often being incapable of anticipating some eventual side-effects because of lack of knowledge at the time. Some classical examples ofthis possible shortsightedness are the over-refinement of foods as in themilling of grains, Nobel and his hopes for dynamite, the aeroplane inwarfare, lead compounds in gasoline, boron additives in some rocket fuels,elemental phosphorus in stick matches, the ionizing radiations from radium,mercury compounds in factory wastes, the internal combustion engine inareas of atmospheric inversion layers, the use of oleander and castor-beanplants as ornamentals, and many others, These and even more recent de-velopments or practices have now focused more scientific attention on theenvironment as a whole, for it has become obvious that this massive infil-tration of the total environment by foreign chemicals must be curtailed in itsentirety, in some instances, and stopped altogether in others. This reali-zation has arrived because the past hazards have been recognized, experiencesof many previously unanticipated side effects have been assimilated, andscientific attention in this area has been simultaneously possible and available.

This sort of attention in agriculture has been strongly focused on pesticidechemicals, for they are required in large amounts wherever intensive agricul-ture is practised and they are usually chemicals that in small amounts arealso toxic to mammals, amphibians, birds, and fish. Arsenic compoundswere long used for codling moth control in deciduous fruit orchards, andafter many years it was found that many orchard soils had accumulatedenough arsenic to become phytotoxic. DDT, an organic chemical, inevitablyreplaced the arsenic insecticides because of greater efficiency and consequentrequirement of fewer applications at lower dosages. Based upon existingknowledge at that time, it was felt that DDT falling upon the soil could notlong survive the living soil environment, and that the extremely low solu-bility of DDT in water precluded its movement by leaching from the area ofapplication. It has taken ten years of broad experience to demonstrate thatboth presumptions are only partial truths, but this recognition plus medicaland pharmacological concern over the total body burden of DDT and otherorganochiorine compounds have resulted in increasing voluntary andsometimes government curtailment of the agricultural uses of the morepersistent of these materials except in emergency pest-control situations.

The point behind these bits of the history of chemicals dispersing intoenvironmental niches is that these possibilities are no longer ignored, butrather are anticipated as probabilities, and are quietly but systematicallyevaluated. Their occurrence, prevalence, mitigation, and curtailment tominimum standards, commensurate with probable hazard to any segmentof the environment, are of great concern to responsible agencies andindividuals, and are under aggressive investigation by more than enoughqualified research groups. In fact, these interests and concerns are so wellestablished now that some investigators are even guilty of seeking newniches and new possible contaminants to investigate. Information alongthese lines that has accumulated over the past 25 years clearly demonstratesthat a very few pesticide chemicals (e.g., DDT, dieldrin) are major long-term contaminants of our total environment, and that several of them(e.g., endrin) are localized contaminants to the point of jurisprudential

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interference with the production of certain root crops and of unquestionedinterference with some of the local wildlife. As Gunther3 has stated, a"qualified (pesticide) residue analyst with proper equipment could findmeasurable DDT in any nonfossil sample presented to him, and with enoughtime and patience could find several other pesticides as well."

According to present indications, the need for chemical pest-control agentswill continue in emergency situations in agricultural production, as theireffects are sufficiently immediate and final to save a crop; other existing andpostulated pest-control measures are slower in action (biological control,insect hormones, chemosterilants, chemical interruption of diapause) andmore expensive (poisoned baits, attractants and repellents, radiation sterili-zation). Adequate non-chemical control of pest fungi does not seem to be arealistic possibility at present. It is certainly clear, however, that steadyefforts will continue to be made to develop and refine any practicable methodof non-chemical pest control to substitute wherever and whenever possiblenon-persistent pesticides for those established to be persistent, to 'rotate'pesticide chemicals in a local area when possible, to confine pesticide chemi-cals to the target areas, and to use the least persistent chemical when pesticidetreatment is required. Unfortunately, for the foreseeable future, the eco-nomics of various effective pest-control measures available will usuallydictate the treatment utilized, as with the continuing extensive use of dieldrinfor grasshopper control on the cattle rangeland pampas areas of Argentinadespite possible excessive residues of this versatile insecticide in the resultingbeef.

LEGISLATIVE CONTROL OF PESTICIDE RESIDUESThose countries that have enacted comprehensive pesticide residue

legislation are listed in Table 6 with a few typical tolerances to illustrate the

Table 6. Examples of countries with comprehensive legislation to control pesticides and theirresidues in foodstuffs, with selected illustrative tolerances.

TheInsecticide Austria Canada Italy Japan Netherlands Germany EECa U.S.A. U.S.S.R.

CarbarylChiordane

.— 200-3

300-2

——

3-001

30zero

300-lb

1003

—zero

DDT — 70 1-0 & I 1-0 10 10 1-0 05Malathion — 4 &8 30 — 30 0-5 — 8 8Parathion — 1-0 05 0-3 0.5 0-5 05 1-0 1-05Dieldrin zero 0-1 02 — 0-1 zero 0lb 0-05 zeroLindane — 10 20 05 2-0 2-0 2-0 10 —HeptachlorAldrin

—zero

0-101

0-20-2

——

010-1

zerozero

0-lb01b

zero8005

zerozero

Rotenone — safe — — 0-04 — safe —

a Proposed; about 35 tolerances will be adopted summer 1969, with 60 in 1970.b Individually or combined.C Including metabolites.1 Some exceptions at 0-1 ppm.

still existing divergences of opinion among pharmacologists, toxicologists,and legislative bodies around the world. Many other countries are activelyconsidering the establishment of this type of legislation, to control the'residue quality' of their own agricultural production for both domesticconsumption and for export purposes, to control imports of foodstuffs, and toassure the quality of foodstuffs in international trade. Among those countries

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with some tolerance restrictions are Australia, Austria, Belgium, Canada,Denmark, England, Finland, France, Peru, Poland and Sweden; countriesactively involved in establishing pesticide residue research and evaluationcentres and in the outside training of qualified pesticide residue analystsinclude Argentina, Brazil, India, Norway, Spain, Thailand, the Philippinesand the United Arab Republic. Those countries which have not initiatedany activities in this area will be forced to do so by internal and internationalcompulsion originating from individuals, agencies, and foodstuff dis-tributors concerned with the maintenance of public health and also from therealization that pesticide residue tolerances could serve as very effectivetrade barriers. Numerous individuals have expressed fears that toleranceswill sometimes be exploited as trade barriers; such a situation would indeedbe deplorable, for the tolerance concept is based upon the best availablescientific evidence of safety in use, and political prostitution of this conceptwould make a hollow mockery of the vast scientific effort underlying realistictolerance values.

The imposition of these legally permitted amounts of pesticide residues infoodstuffs in any country implies market-control implementation of thelegislation. In the absence of adequate governmental laboratories and residueanalysts, recourse can be had to 'certificates of residue compliance' requiredof the producer or importer of the foodstuff, a situation requiring residueanalyses of that particular lot somewhere between production and distri-bution to retail markets. Another recourse is to impose the often-used'minimum intervals' required between application of the pesticide andharvest of the crop, on the philosophy that a few pilot analyses of cropsfrom the local area, or that experiences and residue data accrued elsewhere,can be broadly applied to a particular pesticide and a particular crop in thelocal situation adequately to protect the consumer. In general, this 'mini-mum interval' concept is tenable and dependable, for it is based upon thetime required after application for a pesticide deposit to attenuate or other-wise lose its original identity sufficiently to be well below the tolerance valuefor that pesticide chemical on and in that crop. A 'minimum interval' mustaccommodate the time required for the maximum initial deposit achievableunder the extant 'good agricultural practice' to decrease to the desiredlevel. Several countries utilize both tolerance and 'minimum interval'requirements, whereas some other countries currently utilize only the'minimum interval' requirement, probably as an interim measure awaitingsome sort of international agreement on tolerances for major-use pesticidechemicals on at least the major (basic food) crops (Table 7).

These alternate recourses to establishing compliance with tolerances arenot a satisfactory permanent substitute for governmental-sponsored moni-toring and surveillance programmes to assure continuing protection of thepublic health from possible over-tolerance amounts of pesticide residues infoodstuffs. Even though it is internationally generally agreed by toxicologistsand pharmacologists that all tolerance levels should incorporate elaboratesafety factors (as much as 100 times in some instances), the variety of pesticidechemicals in daily use, the fact that a given pesticide may appear as a residuein a number of prepared foods, the ever-present possibilities of pesticide—pesticide or pesticide—drug interactions, and the possibly exaggerated

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Table 7. Examples of legislative control of pesticide residues in foodstuffs[updated from Gunther and Ott (1966)6]

Timing Sources afCountry Residue control programme restrictions residue data

Australia State jurisdietiona Optional0 StateAustria Federal law Occasional' StateBelgium Regulated by decreea Regulated State, institutesBrazil State jurisdiction Occasional' State, institutesCanadad Compulsory, comprehensivea Regulated' Applicant, stateDenmark State jurisdiction None Ministry of AgricultureFinland State jurisdiction Occasional' StateFrance Restricted by decrees Regulated0 State, universitiesGreat Britain Voluntary, new chemicals Regulated" Government chemistsGreece Compulsorya (olives, citrus) Regulated State, institutesIndia State jurisdiction Optional" StateIndonesia State jurisdiction Occasional' StateIsrael State jurisdiction Regulated State, institutesItaly Compulsory, comprehensivec Regulated ProvincesJapan Compulsory, partial' Regulated StateLebanon State jurisdictiona 0 Occasional' InstituteNew Zealand Regulated by law Regulated StateNorway Partiala, S Probable' InstitutesPeru Partial' b Probable' StatePoland Compulsory Regulated State, industriesSpain Partiala, S Probable' InstitutesSweden State jurisdiction Regulated' StateSwitzerland Regulated Regulated' CantonsThailand Partial " Probable' InstitutesThe Netherlands Comprehensive Regulated State, institutesThe Philippines Partiala, S Probable' InstitutesTurkey Government advisors Occasional' StateUnited Arab Republic Comprehensive Probable' Ministry of AgricultureUnited States" Compulsory, comprehensive Regulated VariousU.S.S.R. Compulsory, comprehensive Regulated National Commission'iv. Germany Comprehensive Probable' States, institutes,

industry

a Certain materials prohibited.b Extensive revision anticipated or in progress.

Not by statute, but minimum iotervsl is often recommended on the label.a Tolerances for aidrin, dieldrin, and heptachior revoked.6 P. de Pietri—Tonelli'5.I Fukunaga and Tsukano".e DDT prohibited after 1 January 1970.0 Several tolerances in the organochlorine group recently revised downwards.

responses to pesticides of the very young, of the very old, and of those otherindividuals on special diets, dictate the wisdom of adhering rather closely toscientifically established tolerances.

In the United States, about 50,000 samples of harvested crops have beenanalyzed by state and federal agencies for pesticide residues each year forseveral years, with the conclusion that only about 2.5% of both our domesticand our imported foodstuffs bear illegal residues, and these are usually only'slightly illegal'. Among other requirements, realistic tolerances that willpermit the continuing safe use of pesticide chemicals must be based upon themaximum amounts of the parent chemicals (or sometimes including majortoxic metabolites or other in situ alteration products) that could persist toharvest (or sometimes sale) resulting from the biologically-established'good agricultural practice'. On an international basis, just what constitutes

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'good agricultural practice' for a particular crop is somewhat controversial,for different countries and even different growing areas within one countrymay have different pests and pest-complexes, cultural practices, meteorolo-gical conditions during growth of the crop, pesticide application equipmentand techniques, and other factors which preclude the internationallyuniform establishment of pesticide type required, tin1ing, formulation, dosagemanner of application, and minimum intervals before harvest. Also, in socountries many commodities are commercially washed, brushed, trimmed,or otherwise cleansed of dirt and exterior blemishes and decay beforeentering trade channels, and these practices will often substantially reduce atotal residue on and in the freshly harvested commodity. Nonetheless, inmost instances it should be possible by scientific arbitration among thebiologists, toxicologists, and pharmacologists involved to arrive at a 'toler-ance range' that would bracket the maximum, safe residues that could occurfrom the numerous 'good agricultural practices' around the world. Con-ceivably, this range could be either large or small, according to manybiologists. If small, there is no problem; if too large, compromises in the'good agricultural practices' that resulted in generally agreed unsaferesidues would be indicated.

Despite much argument to the contrary, these same considerationsshould be applicable to the so-called basic foods such as milk, wheat, rice,potatoes, yams, and maize. Since any one of these basic foods may comprisethe major part of the total diet of a large number of people, it has been feltthat adequate protection of these people arises only from the lowest possibletolerance for a particular pesticide-chemical necessary in the productionof that crop, whereas higher tolerances could safely apply when that croprepresents a lesser proportion of the diet. This argument is scientificallytenable only if there are enough residue data to support it in terms ofestablishment of the proposed international 'tolerance range', and will befurther weakened by the present wholesome trend to less persistent pesticidesin all of agriculture and to the continuing development of alternate choicesof pesticide chemicals for a given emergency pest infestation.

On the other hand, enforcing recommended 'good agricultural practices'is difficult except through the tolerance mecWanism, with seizure of cropsbearing illegal residues. To be effective, this mechanism implies that theremust be seizures, that these seizures must be publicized and that theviolators of 'good agricultural practice' must be penalized into conformity.The adequate promotion of the intent of tolerance restrictions is not met bywaiting for this penalty approach to become fully effective, however. It isalso clear from experiences in the United States and some other countriesthat detailed application instructions and warnings on the pesticide containerare not always followed by the applicator or farmer. Obviously these labelscannot be completely comprehensive nor can they be technically adequate,but rather must be designed for the level of a lay education in specializedcrops production. Pesticide container labels can and generally do admonishfollowing certain dosage, timing, and coverage restrictions but cannot includesufficient details to indicate how deviations from these details might affectultimate residue loads. In addition, the applicator (especially if he is thefarmer) is rarely informed of the significance of harvest-time residues or how

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they might be affected by dosages, timing, adjuvants, weather, and the otherparameters that affect magnitudes of persisting residues; he is concernedabout adequate pest control, and in the face of a possible lost crop he may beinclined to overtreat unless he is somehow made to realize the probableequally serious economic consequences of illegal residues from overtreatment.

Regulating actual uses of pesticides represents a complex problem.Direct approaches are to impose licensing and registration restrictions forquality and labelling, and to license applicators on a renewable basis. Theindirect approach is represented by the tolerance concept, with seizure anddestruction of the shipment the normal penalty for violations, ratherthan the imposition of criminal penalties. This indirect approach obviouslyprovides only a partial deterrent to the improper use of pesticides in agricul-ture, for it involves completely voluntary compliance by the user. Too oftenthe user is poorly informed and thus unable to make a reasoned judgment ofproper use in unusual circumstances; also, it is not always possible to antici-pate drift to adjoining agricultural areas and biota. Strong, enforceablerestrictions on merchandizing pesticides may therefore be necessary for thisessential effective tolerance compliance in any country.

Probably the most realistic assurance of the continuing conformity offoodstuffs to tolerance requirements is through both private and govern-mental residue monitoring and surveillance programmes, although thelatter can easily assume gigantic proportions. These two quality assuranceprogrammes for foods and feeds have been defined as follows4:

Surveillance programme—to assure legal safety of the item with guidedselection of marketed samples (or just harvested samples). Samples areselected based upon suspicion they may contain residues of illegally usedpesticides or above-tolerance residues of particular permitted pesticidechemicals.

Monitoring programme—to assure legal safety of the item with randomselection of marketed samples (or just harvested samples). Samples areobjectively selected with no suspicion factor, and perhaps with severalpossible pesticide chemicals in mind. This programme is often called'food control', 'market control', or 'compliance programme'.

Since there are available today about 1,000 registered pesticide chemicalsand more than 2,500 commercially standard food items, the resulting numberof analytically conceivable combinations would appear to represent animpossible situation. Several factors reduce this situation to statisticalpracticability.

In the United States, for example, the latest available9 agricultural-usefigures are for 1964 and indicate that 12 insecticides accounted for 85% ofthe total volume of all agricultural insecticides, that DDT and toxapheneaccounted for 46% of this total, and that 67% of this total was applied tocotton, corn, and apples; similarly, 12 herbicides accounted for 85% of thetotal volume of all agricultural herbicides and half of this total was appliedto corn, wheat, and cotton acreages; among the agricultural fungicides, theinorganic materials (mostly sulphur) accounted for nearly 86% of the totalvolume used in 1964. These leading pesticides are listed in Table 8. Thesefigures clearly indicate that 12 organic insecticides, 10 organic herbicides,and 3 types of organic fungicides would be those pesticides most commonly

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FRANCIS A. GUNTHER

Table 8. Leading agricultural pesticides in the United States in 1964 according to volumeconsumption by the farmer9

Insecticides Herbicides Fungicides

Active Total useingredient (x 1,000 Ib)

Active Total useingredient (x1,000 Ib)

Active Total useingredient (x 1,000 lb)

Toxaphene 38,911DDT 33,543Carbaryl 14,946Aidrin 11,148Methyl parathion 9,985Parathion 6,426Malathion 4,768TDE (DDD) 3,387Strobane 2,715Diazinon 2,310Azinphos methyl 2,273Endrin 2,169

2,4.D compounds 34,454Atrazine 10,899Borax 4,828Calcium cyanamide 3,906Propanil 3,852CDAA 3,6652,3,6-TBA 2,215Dalapon 2,0622,4,5-T 1,655MCPA 1,516Amiben 1,212Diuron 1,124

Suiphura 136,823Dithiocarbamates 12,814Copper saltsa 6,715Phthalimides 5,840Zinc saitsa 1,294Quinones 1,044Othersa 5,549

a May include uses other than as a fungicide.

encountered among any residues present in the foodstuff. The U.S. Foodand Drug Administration2 lists in order the 10 most commonly encounteredresidues as in Table 9; it is not clear why this table contains only organo-chlorine insecticides and only five out of the six organochiorine compoundslisted under 'insecticides' in Table 8.

Table 9. Most commonly encountered pesticide residues in domesticand imported foodstuffs2

Domestic samples Import samples

DDT DDTDDE DDEDieldrin DieldrinTDE (DDD)Heptachior epoxide

TDE (DDD)BHC

Lindane LindaneBHC AldrinEndrin KeithaneAidrin Heptachlor epoxideToxaphene Endrin

Furthermore, any practising economic entomologist, horticulturist, orplant pathologist should be able to advise the residue analyst which few ofthe total number of commercially available pesticides would probably havebeen used in the production of the crop, especially if the growing area andseason were known. If neither of these rationales is pertinent to a particularsample, the latter specialists could certainly eliminate all but a few candidateresidue analytical targets. The oft-used pathetic argument that 'we mustlook for everything in all commodities' is therefore scientifically untenable.On the other hand, the periodic so-called 'market basket surveys' ('totaldiet surveys') of the U.S. Food and Drug Administration do present acomplex residue analytical problem in that the constituent 82 food itemsfrom each of five regions of this country are pureed into 12 classes of similarfoods for ultimate analytical aliquots, -thus losing their identities as crop

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items and thus incorporating into the mixture probable pest-control treat-ments from many production areas within one or more regions; advicefrom agriculturalists, plus years of experience in encountering residues inboth surveillance and monitoring programmes, plus unusual public healthinterest in only a few chemicals, plus certain restrictive residue analyticalcapabilities, have resulted in the following alphabetical list of pesticidechemicals sought in these very informative and expectedly encouragingsurveys2:

Aidrin KeithaneBHC LindaneBulan MalathionChiorbenside MethoxychiorChlorobenzilate Methyl parathionChiordane OvexChiorthion ParathionCIPC PCNB2,4-D esters and ethers Perthane and olefinDacthal ProlanDDE RonnelDDT isomers StrobaneDiazinon 2,4,5-T estersDichioran TCNBDieldrin TDEDilan TedionDyrene TelodrinEndrin TetraiodoethyleneEthion ThimetEPN Thiodan IFolpet ToxapheneHeptachior TrithionHeptachlor epoxide VegadexHexachlorobenzene

Certain additional pesticides such as a few carbamates and some of the2,4-D type compounds are looked for only occasionally because of limitedanalytical resources.

Another factor reducing this analytical impossibility to practicability isthat there are comparatively few major food items in the 12 classes com-prising the average diet; for example, the U.S. Food and Drug Administra-tion has concluded that 82 food and drink items are sufficient to be typical ofthe four major regions in the United States and will include considerationsof economic status as well1. It is obvious that exotic and luxury foods neednot require the frequent residue analytical attention accorded those morestandard items of daily diet and especially those consumed in quantity byany dietary group.

ENFORCEMENT OF TOLERANCESAs mentioned in the preceding Section, the long-term enforcement of

pesticide residue tolerances is undoubtedly best conducted through govern-ment-sponsored periodic residue analyses of foods, rather than by means of'certificates of conformity to residue requirements'. Both of these enforce-ment devices may place ultimate responsibility for illegal residues uponeither the farmer or the applicator, if different; the average farmer canhardly be expected to be thoroughly informed on the many field factors thatinfluence the magnitudes of harvest residues, yet licensed applicators must be

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knowledgable in this area if they are to continue to provide satisfactorypest-control while still meeting the imposed limitations of natures andamounts of residues permitted on and in the crop. Occasional violations of'good agricultural practice' will occur in any event, and it is these occa-sional illegal residues that by law must be kept off the market; as statedearlier, about 25 % of the more than 125,000 crop samples officially ana-lyzed in the United States over the past five years was found to exceed legaltolerances or other administrative guides for excessive residues.

If governmental agencies conduct these residue analyses, there is thestrong probability that the sampling and analytical methods used will bemore uniform and standardized in important details from governmentlaboratory to government laboratory than would be likely among the verylarge number of private and industrial laboratories that would otherwise beinvolved. Nonetheless, in the United States several producing and processingsegments of the food industry have commendably established their ownpesticide residue 'quality assurance' programmes not only to assure con-tinuing safe pesticide residues in their products but also to permit the usefulestablishment and maintenance of changing pesticide residue patterns withintheir areas of supply, for particular pest-control problems are often highlylocalized and seasonal. Some of these food processors will not purchasecrops without analytical assurances that any residues present are belowpermitted tolerance levels, whereas others rely largely on accurate anddetailed pest-control records, maintained by the grower, to assure compli-ance with 'good agricultural practice' and thus very practical compliancewith tolerance restrictions, as discussed earlier.

To be effective and reliable, any residue surveillance or monitoringanalytical programme must meet a number of very stringent requirements,with emphasis on suitably rapid accumulation of final residue data to stopthe shipment or sale of the commodity:

Sampling. Someone must decide what constitutes adequately sized andreproducible samples of each commodity and how to select them to representthe mean residue burden in the lot, the probable maximum residue burdenin the lot, or the range of residues present in the lot; depending upon thepesticide present, the major location of the residue on or in parts of thecommodity, and the unit size of the commodity, at least duplicate samplesare always required for the present purposes. Similarly, it must be decidedwhere to sample in the production scheme of the commodity, as in the fieldat harvest, after any packing-house operations normally involved, or in thewholesale or retail markets. These decisions must be defensible.

Preparation of sample for analysis. Someone must decide whether the sampleunits are to be washed (and if so, how?), trimmed, brushed, seeded, freedof any decayed parts, etc. In the United States, tolerances are based by lawupon the raw agricultural commodity as shipped, and the U.S. Food andDrug Administration10 directs "Remove only obviously decomposed leaves,berries, etc. Do not wash (except root crops should be rinsed free of adheringsoil), cull, strip, or otherwise use procedures which might be used in prepar-ing the food for consumption". Some obviously required exemptions byregulation have been established, however, such as removing shells fromnuts, caps from strawberries, stems from melons, crowns from pineapple, and

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extraneous material from garlic cloves. In this connection, it must be remem-bered that in this country most raw agricultural commodities are processedin packing houses before being packed for entry into market channels.Depending upon the commodity, this processing may include brushing(carrots, potatoes, etc.); dusting (dates), washing (apples, pears, etc.),washing and waxing or oiling (citrus fruits, cucumbers, etc.), partial trim-ming (cabbages, celery, etc.), and other treatments. Some commodities arepacked without being treated in any of these ways (melons, tomatoes, etc.).

Storage of samples. Even frozen samples should not be stored longer than30 days without analytical proof that the sought chemical does not undergostorage alteration under such conditions. Frozen storage in glass or plasticcontainers often causes sweating, with possible consequent transfer ofsome of the sought chemical to the walls of the container.

Processing of samples. Acceptably rapid processing procedures for trans-ferring the sought chemical(s) from the analytical aliquot of the parentsample into a suitable solvent may vary markedly from crop to crop andfrom chemical to chemical. Probably the nearest approach to a universalsolvent for this purpose (except for dry products) is acetonitrile, but there aremany exceptions in the voluminous literature on this broad subject. Sample'extracts' should be cleaned up and analyzed as promptly as possible unlessproof of non-deterioration during this storage is available.

Cleanup. This literature is also voluminous, but the well-known Millsprocedure and its several modifications are nearly generally applicable formost pesticide chemicals destined for further gas chromatographic segrega-tion and estimation. For surveillance and monitoring purposes, a singlereasonably rapid, basic type of cleanup adequate for the determinativetechnique(s) is almost mandatory.

The analysis. Again, suitably rapid methods are legion, depending upondesired accuracy, reliability, reproducibility, and minimum detectability.Besides establishing these parameters, someone must also decide if theresidue analyst should look only for the parent compound or also for certainmetabolites or other alteration products, and at what levels. Samples clearlybelow tolerance maxima are presumably of no further interest, but samplesat or above tolerance levels should be examined further with an independentback-up or buttressing method, for a claim of illegal residues may representa large loss to grower or shipper and result in a lawsuit. Back-up residueanalytical methods generally need not be rapid ones, but they must be asspecific and as reliable as possible and defensible in a courtroom. By con-census among many residue authorities around the world, the followinglimits of accuracy for most of these analyses seem to be realistic:

10 ppm ± 10%1 ppm ± 10%

01 ppm ± 20%0.01 ppm ± 50%

0.001 ppm ± 100%Some authorities feel the last value should be +200%.

Multiple residue methods. In principle, these methods'5 utilize a single 'extrac-tion' (this usage of this word is incorrect for it implies quantitative transfer

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FRANCIS A. GUNTHER

of the desired solute from substrate to solvent) and a single laboratorycleanup, followed by gas or thin-layer chromatography for final segregationof sought compounds before apparent identification and quantitative meas-urement. Multiple methods extant for most organochiorine pesticides andfew organophosphorus pesticides utilize partitioning from acetonitrile orisopropyl alcohol-hexane as preliminary cleanup, followed by gas chroma-tographic segregation and detection by both electron-capture and thermionicor other more specific detectors. Thus, in a few hours about 60 pesticides(including some metabolites) can be recognized, measured, andreasonably characterized in the extractives from a large variety of foodstuffs.For adequacy of results, however, these multiple residue methods must besupervised closely by a qualified and experienced residue analyst, for availableprocedures and supplies (e.g., the Florisil in the Mills procedure) are not yetstandardized for completely consistent results without elaborate internalstandards and other guides to establish aberrant behaviour in the totalmethod.

Gas chromatography and thin-layer chromatography are excellentmutually buttressing techniques in those instances where unusual care mustbe taken to assure illegality of residues present. For maximum reliability,each should be applied to separate aliquots of the parent 'extract' aftersuitable and different preliminary cleanup (if required) because analyticalresults depend upon the total method from sample to readout. With astandardized 'extraction' and preliminary cleanup and partial segregationas in the Mills procedure, however, both can realistically be applied toaliquots of the Mills procedure fractions to achieve support of the finalsegregative and determinative technique. Proper gas chromatographyaccomplishes both operations, whereas thin-layer chromatography can alsoachieve excellent segregation but must be followed by other quantitation,as by gas chromatography, polarography, spectroscopic behaviour, etc.It should also be borne in mind that the gas chromatographic detector onlyreports the degree and maintenance of segregation achieved and amplitudeof stimulus received'2.

AUTOMATED RESIDUE ANALYSESThese programmes involve the routine analysis of large numbers of the

same or different types of samples of foodstuffs for a variety of pesticides, or'screening' in this usage. There are at least three types of screening12:

Segregative screening—separating above-tolerance (or other sought para-meter) from below-tolerance samples, with an acceptable quantitativelatitude, as discussed earlier, and with usually only one sought pesticide inmind.

Constituent screening—detecting a variety of sought pesticides in the samples,with previously established limits of minimum detectability.

Quantitative screening—determining or otherwise adequately establishingthe amounts of sought pesticides present in the samples, again with previouslyestablished limits of detectability but also with previously established relia-bility and reproducibility.

With sharply increasing emphasis around the world on pesticide chemicaltolerances and the consequent necessity to analyze, on a continuing basis,

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PESTICIDE RESIDUES IN ThE TOTAL ENVIRONMENT

large numbers of samples of foodstuffs for tolerance conformity, it hasbelatedly been realized in many countries that there is an acute shortage oftrained residue analysts; to be of any value whatsoever all of these analysesare necessarily complex and demanding and require the direct attention ofqualified and experienced residue analysts, even with the multiple residuemethods. It is clear, then, that routine screening procedures to demonstratethe tolerance-level 'presence' or 'absence' of groups or categories ofpesticide chemicals will become increasingly important everywhere'6. Thus,with a tolerance as an analytical target value, partially or totally automatedscreening would partition a set of samples into those comfortably belowtolerance vs. those at or above tolerance, within the acceptable deviationguidelines presented earlier; the available expert attention could then bedirected to those few percent of the samples requiring close and carefulscrutiny for enforcement action. The inherent advantages of reliability,reproducibility, and speed of the automated analytical system are essentialto the successful production of adequate numbers of routine residue analysesin these escalating international residue monitoring and surveillanceprogrammes6.

The available pesticide chemicals may be loosely categorized into some-times overlapping groups according to their contents of elements other thancarbon, hydrogen, and oxygen:

Antimony MercuryArsenic NitrogenBromine PhosphorusChlorine SulphurCopper TinLead ZincManganese

Most pesticide residues occur in marketed foodstuffs within the range001 to 10 ppm. Totally automated residue analyses are not yet directlyadaptable to the lower ranges, yet there are possible some immediateapplications to the present problem for tolerances ranging from aboutO2 to 100 ppm. For example, screening operations of the types describedcould be considered trifacially: analyses for characteristic elements, analysesfor characteristic functional groups or moieties, and analyses for certainachievable types of biological activity. With the current exception of nitrogen,the elements listed above could be determined in organic and inorganicpesticide residues in automated assemblies of unit-operation modules in theabove approximate range. Functional group analyses merely await auto-mation, as for aldehyde, ketone, phenol, trichioromethyl, etc., moieties inthe same range. Achievable automated measurements of biological activitiesof interest here would include cholinesterase activities before and after oxida-tion of any thionophosphates present to phosphates (oxons), with minimumdetectabilities below 01 ppm.

In addition, automated combinations of modules are capable of per-forming almost any laboratory operation, excluding centrifugation; theymay be likened to unit processes, as distillation, hydrolysis, steam distilla-tion, evaporation (concentration), dialysis, extraction, partition distribution,homogenization, and others. Determinative automated modules includevisible colorimetry, ultraviolet spectrometry, fluorometry, polarography,coulometry, flame photometry, and others.

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FRANCIS A. GUNTHER

Where minimum detectability requirements are not too severe, totallyautomated procedures are achievable, starting with 10 to 30 g of foodstuffor soil sample carried through automated modules to chart record. In otherinstances, automated procedures could be used to homogenize and 'extract'samples, then clean them up and present them as concentrates for manualor automatic injection into a gas chromatograph. In still other instances,split-stream techniques could be used to determine on a single sample suchuseful parameters as total organic chloride, phosphorus, and sulphur valuesand their ratios, plus cholinesterase activity both before and aftermild oxidation.

In the pesticide residue field, several examples of these three basic typesof automated analyses, as well as direct applications of isolated unit-opera-tion techniques, have already appeared in the literature.

References'J. G. Cummings. Pesticides in the total diet. Residue Rev. 16, 30 (1966).2 R. E. Duggan and K. Dawson. Pesticides—A report on residues in food. NAG News Pest. Rev.

25(6), 3 (1967).F. A. Gunther. Advances in analytical detection of pesticides. In: Scientglc Aspects of Pest Control,pp. 284—285. Nat. Acad. of Sci.—Nat. Res. Council, pubi. No. 1402, Washington, D.C.(1966).F. A. Gunther. Insecticide residues in California citrusfruits and products. Residue Rev. 28, 1 (1969).F. A. Gunther and L. R. Jeppson. Modern Insecticides and World Food Production. Chapmanand Hall, London (19(30).

6 F. A. Gunther and D. E. Ott. Automated pesticide residue analysis and screening. Residue Rev.14, 12 (1966).W. Perkow. Die Insektizide. Alfred Huthig Verlag, Heidelberg (1956).

8 A. Stefferud (editor). Insects, The Yearbook of Agriculture. U.S. Superintendent of Docu-ments, Washington, D.C. (1952).' U.S. Dep. of Agriculture. Pesticide Rev. Washington, D.C. (1968).

10 U.S. Food and Drug Administration. Pesticide Analytical Manual, periodically revised.Washington, D.C. (1968).

11 W. E. Westlake and F. A. Gunther. Occurrence and mode of introduction of pesticides in theenvironment. Adv. Chem. Series 60, 110 (1966).

12 W. E. Westlake and F. A. Gunther. Advances in gas chromatographic detectors illustrated fromapplications to pesticide residue evaluations. Residue Rev. 18, 175 (19(37).

13 P. de Pietri-Tonelli. The regulation of pesticides in Italy. Residue Rev. 27, 1 (1969).14 K. Fukunaga and Y. Tsukano. Pesticide Regulations and residue problems in Japan. Residue Rev.

26, 1 (1969).15J A. Burke. Development of the Food and Drug Administration's method of analysis for multiple

residues of organochlorine pesticides in foods and feeds. Residue Rev. 34, (in press) (1970).16 U.S. Dept. of Health, Education and Welfare. Report of Secretary's Commission on Pesticides

and their relationship to environmental health p. 174. Washington, D.C. (Dec. 1969).

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