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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

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chapter 17

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
What is Risk?
  • Risk: possibility of suffering harm from a hazard
human health risks
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
biological risks
Biological Risks
  • Disease: any impaired function of the body with a characteristic set of symptoms
biological risks1
Biological Risks
  • Infectious diseases: those caused by infectious agents, known as pathogens
    • Ex: pneumonia and venereal diseases
  • Bacteria:
    • Cholera
    • Tuberculosis
    • Syphilis
  • Virus:
    • HIV/AIDS
    • Hepatitis
    • Ebola
  • Protozoa:
    • Malaria
what causes disease
What causes disease?
  • Infectious agents (pathogens) that spread by:
    • Air
    • Water
    • Food
    • Body fluids
    • Vectors (nonhuman carriers, like mosquitoes)
biological risks2
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
historical diseases
Historical Diseases
  • Plague
  • Malaria
  • Tuberculosis
emergent diseases
Emergent Diseases
  • Ebola
  • Mad Cow Disease
  • Bird Flu
  • West Nile Virus
chemical risks
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
Toxicology Studies
  • Retrospective 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 studies1
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


Dose: the amount of a substance that a person has in their body

Can be:





“The dose makes the poison”

dose response studies
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
ld 50

LD50 = 5.3

do the math
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: materials that kill at a very small dose (50 milligrams or less per kilogram of weight)
dose response studies2
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

  • 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




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

do the math1
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?

  • 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: how long a chemical remains in the environment
qualitative vs quantitative
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)
risk analysis1
Risk Analysis

Risk =

Probability of being exposed to a hazard


Probability of being harmed if exposed

risk analysis2
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 regulation1
Chemical Regulation
  • Trade-off:
    • Greater safety with slower introduction of beneficial chemicals


    • Greater potential risk with a greater rate of discovery of beneficial chemicals
concentration practice problems
Concentration Practice Problems
  • How much is 6 ppm in ppb?
  • What concentration is 4,000 ppt in ppm?










6,000 ppb









0.004 ppm