Human Health and

Environmental Toxicology

Human Health

Overall human health best assessed by:

1) Life expectancy (years)

2) Infant mortality (# deaths up to age one per 1,000 live births)

Life Expectancy / Infant Mortality Selected countries, 2004 data

Life Expectancy (years)

Infant Mortality (# deaths up to age one per 1,000 live births)

Japan

Source: U.S. Census Bureau, International Database

81.2 3.3

Switzerland 80.4 4.4

Sweden 80.4 2.8

Mozambique 40.3 130.8

Zimbabwe 36.7 60.7

Angola 36.6 191.2

Health Issues in Highly Developed Countries

Leading causes of death in US:

Cardiovascular diseases, cancer, & chronic obstructive pulmonary disease

Health Issues in Developing Nations

Malnutrition, unsafe water, and poor sanitation

Leads to . . . Numerous infectious diseases

Compounded by poor healthcare, leads to . . .

Lowered life expectancy

Emerging v. Reemerging DiseasesEmerging –

Not previously observed within humans:

AIDS, Lyme disease, West Nile virus

Reemerging –

Existed previously, becoming more common again:

Tuberculosis, Yellow fever, Malaria

Determining Health Effects of Environmental Pollution

Children and chemical exposure

Determining Health Effects of Environmental Pollution

Identifying Cancer-Causing Substances• Carcinogen – Environmental agent known to

induce cancer. • Chemicals commonly tested with rats

but, is the dose equivalent?• Can you extrapolate the results to

humans?

Determining Health Effects of Environmental Pollution

Chemical Mixtures• Most studies examine effect of single

chemical exposure.• What happens when exposed to

multiple chemicals?• Additive effect?• Synergistic effect?• Antagonistic effect?

Decision Making and Uncertainty

Risk assessment:

Low High

Representative Cellular Targets for Toxic Action

11

Three Stages in Carcinogenesis

Stage Normal cell Carcinogenic agent

Initiation • Genotoxic initiator

• Co-carcinogenInitiated cell

Promotion • Promoter•

Immunosuppressor Cancer • Hormones

• Dietary compounds

• Other

Progression Invasion

Metastasis

{{

{

Metabolic Activation of Benzo(a)pyrene

2,3,7,8-Tetrachlorodibenzo(p)dioxin

Lock and Key Model for Toxic Action

• Disrupt normal steroid action and may influence the development of endometriosis.

• A by-product of manufacture and combustion of chlorinated phenols and is considered by some to be one of the most toxic substances ever released into the environment.

Toxicological/Ecological Relevance and Time Scale of Toxic Response for Levels of Biological Organization (McGarthy and Shugart, 1989)

16

Idealized Plot of Dose-Response Relationship (Health 1987)

Biomagnification of Pesticides in Aquatic Food Chains (Connell 1990)

Possible Movement and Fate of a Contaminant after Absorption into the Bloodstream of a Fish (Health 1987)

19