C

CH 17HUMAN HEALTH AND

ENVIRONMENTAL RISKS

Three categories of human health risks

Biological- disease

Physical- natural disasters

Chemical- pesticide exposure

Biological Risks

Infectious diseases- those caused by

infectious agents, known as pathogens.

Biological Risks cause the most human

deaths.

Examples: pneumonia and venereal

diseases

Biological Risks

Chronic disease- slowly impairs the

functioning of a person’s body.

Acute diseases- rapidly impair the

functioning of a person’s body.

Leading Health Risks Worldwide

Historical Diseases

Plague- bacterium carried by fleas

Malaria- protist carried by mosquitoes

Tuberculosis- bacterium infects the lungs

Emergent Diseases(New Diseases)

HIV/AIDS- viral

Ebola- viral

Mad Cow Disease- prions (deadly proteins)

Bird Flu- viral

West Nile Virus- viral

Chemical Risk

•Pharmaceuticals

• Insecticides

•Herbicides

•Fungicides

•Cleaning products

• Industrial Chemicals

Chemical Risks- Toxicology

Neurotoxins- chemicals that disrupt the nervous system

Carcinogens- chemicals that cause cancer

Teratogens- chemicals that interfere with the normal

development of embryos or fetuses

Allergens- chemicals that cause allergic reactions

Endocrine disruptors- chemicals that interfere with the

normal functioning of hormones in an animal’s body

Determining Harmful Chemical Concentrations

Dose response Studies-LD50- lethal dose that kills 50% of the individuals in the

test population

ED50- effective dose that causes 50% of the animals to display the harmful but nonlethal effect

Dose Response Studies

• Threshold- the dose at which the effect can be

detected

•Usually mice and rats are used in the study

•Most common response measured is mortality

•Data generally produces an s-shaped curve

• LD50 assesses the relative toxicity of a chemical

Testing Standards

• EPA holds authority to regulate the effects of chemicals

on humans

• Toxic Substances Control Act 1976

• Federal Insecticide, Fungicide and Rodenticide Act- FIFRA

•However- with 10 million species, no chemical can be

tested on every organism.

Routes of Exposure

Bioaccumulation

Bioaccumulation- an increased

concentration of a chemical within an

organism over time

Biomagnification

Biomagnification- the

increase in a chemical

concentration in

animal tissues as the

chemical moves up the

food chain.

Persistence

Persistence- how

long a chemical

remains in the

environment

Risk Analysis

Qualitative Risk Assessment

Making a judgment of the relative risks of

various decisions

Probability- the statistical likelihood of an

event occurring and the probability of that

event causing harm

Quantitative Risk Assessment

The approach to conducting a quantitative

risk assessment is:

Risk= probability of being exposed to a

hazard X probability of being harmed if

exposed

Stockholm Convention

In 2001, a group of 127 nations gathered in

Stockholm, Sweden, to reach an agreement on

restricting the global use of some chemicals

12 chemicals (“The Dirty Dozen”) were to be banned,

phased out, or reduced

These include DDT, PCBs, and certain chemicals that

are by-products of manufacturing processes.

•Many environmental contaminants (and even

foodstuffs) are considered differently by scientific

groups and agencies with regard to their safety. It

is, therefore, up to the “consumer” in many cases

to make a judgment call as to how much exposure

is reasonable, based on available information.