Chapter 17 Human Health and Environmental Risks

Three categories of human health risks Physical – excessive exposure to UV radiation or radon Biological - associated with disease Chemical – naturally occurring as well as synthetically produced

Leading causes of death in the world

Biological Risks Infectious diseases- those caused by infectious agents, known as pathogens. Chronic disease- slowly impairs the functioning of a person’s body. Acute disease- rapidly impairs the functioning of a person’s body. Epidemic – rapid increase Pandemic – epidemic over a large geographic area

Leading Health Risks

Historical Diseases Plague – aka bubonic plague or black death Caused by bacteria spread by fleas Most recent pandemic in Asia in early 1900’s Malaria Caused by a parasitic protist carried by mosquitoes Tuberculosis Caused by airborne bacteria Serious problem today is drug-resistant strains

Emergent Diseases HIV/AIDS – spread by contact with infected bodily fluids Ebola – extremely high death rate Mad cow disease – caused by prions; spread to humans through ingestion of infected meat Bird flu – aka H1N1; spread from infected domesticated birds West nile virus – spread from wild birds to humans via mosquitoes

Transmission of pathogens

Chemical Risks Neurotoxins- chemicals that disrupt the nervous system – some insecticides, lead, mercury Carcinogens- chemicals that cause cancer – asbestos, radon, formaldehyde, tobacco Teratogens- chemicals that interfere with the normal development of embryos or fetuses – thalidomide, alcohol Allergens- chemicals that cause allergic reactions – peanuts, milk, penicillin, codeine Endocrine disruptors- chemicals that interfere with the normal functioning of hormones in an animal’s body - hormones

Dose-Response Studies LD50- lethal dose that kills 50% of the individuals Studies are conducted on animals and extrapolated to humans ED50- effective dose that causes 50% of the animals to display the harmful but nonlethal effect Sublethal effects – is the chemical a teratogen, carcinogen, neurotoxin?

LD50 Study

Synergistic interactions- when two risks come together and cause more harm that one would. Example: the health impact of a carcinogen such as asbestos can be much higher if an individual also smokes tobacco.

Routes of Chemical Exposure

Bioaccumulation An increased concentration of a chemical within an organism over time Usually occurs with fat-soluble substances Classic example: DDT

Biomagnification in the food chain - DDT

Persistence How long a chemical remains in the environment

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 were to be banned, phased out, or reduced These include DDT, PCBs, and certain chemicals that are by- products of manufacturing processes.

Risk Analysis

Probability of death in U.S.

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 times probability of being harmed if exposed