1. Human Health and Environmental Risks
Chapter 17
Human Health and Environmental Risks

2. 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)

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

4. 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

5. Leading Causes of Death Worldwide

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

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

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

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

10. 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

11. Leading Health Risks in the World

12. Historical Diseases
Plague
Malaria
Tuberculosis

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

14. Emergent Diseases

15. Pathways of Transmitting Pathogens

16. 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

19. 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

20. 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

21. 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

22. 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

23. 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

24. LD50
LD50 = 5.3

26. 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

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

29. Threshold

30. 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

31. 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 + =

32. Routes of Exposure

33. 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

34. 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?

35. 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

36. Persistence
Persistence: how long a chemical remains in the environment

37. Risk Analysis

38. 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)

39. Probabilities of Death in U.S.

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

41. 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

42. Chemical Regulation

43. 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

44. 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