Human Health and Environmental Toxicology Chapter 7

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 Switzerland Sweden Mozambique Zimbabwe Angola

Health Issues in Highly Developed Countries Leading causes of death in US: Cardiovascular diseases, cancer, & chronic obstructive pulmonary disease Linked to... Obesity

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 Diseases Emerging – Not previously observed within humans: AIDS, Lyme disease, West Nile virus Reemerging – Existed previously, becoming more common again: Tuberculosis, Yellow fever, Malaria

Environmental Pollution & Disease

Persistence Degradation of synthetic pesticides is slow. Many remain in soil / water for years.

Bioaccumulation Natural substances commonly recycle in living organisms. Intake = Output (no long term accumulation) Synthetic substances typically not metabolized. Intake, with little output = accumulation (typically in fat)

Biomagnification

Example: Effect of DDT on bald eagles

Endocrine Disruptors Chemicals that alter hormone production. Ex: PCBs, dioxins, lead, mercury, DDT Hormones have their affect at low doses. Endocrine disruptors act similarly.

Endocrine Disruptors Example: American alligators and DDT spill

Determining Health Effects of Environmental Pollution Toxicant – Chemical that induces adverse response at a certain dose. Toxicity of a chemical is assessed by determining its LD 50 (dose at which 50% of test subjects die due to exposure)

Determining Health Effects of Environmental Pollution Lethal Dose-50% (LD 50 )

Determining Health Effects of Environmental Pollution Effective Dose-50% (ED 50 ) – Dose that induces 50% of test subjects to have some type of effect Dose response curve –

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?

Ecotoxicology Dilution paradigm – “the solution to pollution is dilution” Boomerang paradigm – “what you throw away can come back and hurt you”

Ecotoxicology Case in Point: The Ocean and Human Health

Decision Making and Uncertainty Risks:

Decision Making and Uncertainty Risk assessment: Low High

Decision Making and Uncertainty Risk assessment:

Decision Making and Uncertainty Ecological risk assessment: Extends steps of risk assessment to the impact on all plants, animals, and other organisms in an area.

Decision Making and Uncertainty Ecological risk assessment example: Dams on Snake River

Decision Making and Uncertainty Cost-Benefit Analyses Cost Benefit