Human Health and Environmental Risks Chapter 17 Human Health and Environmental Risks

Warm-Up What are the leading causes of death worldwide? How is the economic development of a country related to disease? Rank the following in order of highest probability of death to lowest probability: Airplane accident Drowning Motor vehicle accident Heart disease Firearm assault (1 in 5,051) (1 in 1,008) (1 in 84) (1 in 5) (1 in 314)

What is Risk? Risk: possibility of suffering harm from a hazard

Human Health Risks Physical – harm caused by environmental factors Natural disasters Sunburn Biological – harm caused by diseases Malaria Influenza Chemical – harm caused by chemicals Arsenic Pesticides

Leading Causes of Death Worldwide

Biological Risks Disease: any impaired function of the body with a characteristic set of symptoms

Biological Risks Infectious diseases: those caused by infectious agents, known as pathogens Ex: pneumonia and venereal diseases

Pathogens Bacteria: Virus: Protozoa: Cholera Tuberculosis Syphilis HIV/AIDS Hepatitis Ebola Protozoa: Malaria

What causes disease? Infectious agents (pathogens) that spread by: Air Water Food Body fluids Vectors (nonhuman carriers, like mosquitoes)

Biological Risks Chronic disease: slowly impairs the functioning of a person’s body Ex: heart disease, cancer, diabetes 70% of all deaths in the U.S. Acute disease: rapidly impairs the functioning of a person’s body Ex: Ebola hemorrhagic fever

Leading Health Risks in the World

Historical Diseases Plague Malaria Tuberculosis

Emergent Diseases HIV/AIDS Ebola Mad Cow Disease Bird Flu West Nile Virus

Emergent Diseases

Pathways of Transmitting Pathogens

Chemical Risks Neurotoxins: chemicals that disrupt the nervous system Carcinogens: chemicals that cause cancer Teratogens: chemicals that interfere with the normal development of embryos and fetuses Allergens: chemicals that cause allergic reactions Endocrine disruptors: chemicals that interfere with the normal functioning of hormones

Toxicology Studies Retrospective studies Prospective studies “Looking back” Monitoring people who have already been exposed to a chemical to determine the effects Prospective studies “Looking forward” Monitoring people who might become exposed to a chemical to determine the effects

Toxicology Studies Epidemiology: field of science that seeks to understand the causes of illness and disease Retrospective and prospective studies allow researchers to determine the effects of chemicals on individuals

Toxicology “The dose makes the poison” Dose: the amount of a substance that a person has in their body Can be: Ingested Inhaled Injected Absorbed “The dose makes the poison” 21

Dose-Response Studies Exposing organisms to different doses of a chemical and then observing their response allows scientists to determine how chemicals affect living things Response: the effect that a substance has on an organism (ex: mortality, change in behavior, etc.) LD50: the lethal dose that kills 50% of the individuals within a test population

Dose-Response Studies Dose (hypothetical units) Percent Mortality 1 0% 2 3 4% 4 10% 5 40% 6 60% 7 90% 8 96% 9 100% 10

LD50 LD50 = 5.3

Do The Math If the LD50 of a pesticide is 20 mg/kg for a mouse, what amount would be considered safe to ingest for a human? (Calculate the “safe” amount by taking the LD50 and dividing it by 1,000) 20 mg/kg ÷ 1000 = 0.02 mg/kg Calculate the maximum amount that a 80 kg man could ingest and still be considered “safe” 80 kg × 0.02 mg/kg = 1.6 mg

Poisons Poisons: materials that kill at a very small dose (50 milligrams or less per kilogram of weight)

Threshold

Dose-Response Studies ED50: effective dose that causes 50% of the individuals to display the harmful, but nonlethal, effect These effects that change the behavior of the individuals or cause harm are called sublethal effects The LD50 and ED50 values for mice are often divided by 1,000 to determine the safe value for humans

Interactions Synergistic interactions: when two (or more) risk factors have a greater effect together than each by themselves Ex: being exposed to asbestos and smoking gives you a 400 times greater chance of developing lung cancer than if you experienced only one of those risks + =

Routes of Exposure

Toxicology Solubility: what can the chemical dissolve in? Water-soluble toxins Oil/Fat-soluble toxins Which do you think is generally “better” for the health of an organism? Water is “better” since it can be diluted Fats aren’t good since chemicals can gather in body fat of animals 33

Do The Math If the element Strogenium has an LD50 of 40 mg/kg, how big of a dose is necessary to kill a 30 kg goat?

Toxicology Bioaccumulation: an increased concentration of a chemical within an individual organism over time The chemical is usually stored in body fat 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 vs. Quantitative Qualitative risk assessment: judging the relative risk of various decisions (ex: low, medium, or high) Judgments based on perception, not on actual data Quantitative risk assessment: determining the probability of an event occurring using data (ex: 83% chance)

Probabilities of Death in U.S.

Risk Analysis Risk = Probability of being exposed to a hazard x Probability of being harmed if exposed

Risk Analysis What is riskier: flying on a plane for 1,000 miles per year or eating 40 tablespoons of peanut butter per year? The probability of a plane crash is low, but the probability of dying if the plane crashes is high The probability of eating peanut butter is high, but the probability of developing cancer from the peanut butter is low Both behaviors produce a risk of 1 in 1 million

Chemical Regulation

Chemical Regulation Trade-off: Greater safety with slower introduction of beneficial chemicals vs. Greater potential risk with a greater rate of discovery of beneficial chemicals

Concentration Practice Problems How much is 6 ppm in ppb? What concentration is 4,000 ppt in ppm? 6 1,000,000 1,000 6,000 1,000,000,000 x = = 6,000 ppb 4,000 1,000,000,000,000 1,000,000 0.004 1,000,000 ÷ = = 0.004 ppm