1. Chapter 17
Environmental Hazards and
Human Health

2. Risks Are Usually Expressed as
Probabilities
Risk
Probability of suffering harm from a hazard
Probability vs. possibility

3. Science: Risk Assessment and Risk Management
Fig. 17-2, p. 437

4. We Face Many Types of Hazards
Biological:
– Pathogen: an organism that causes disease in other organisms
Chemical
Physical
Cultural
Lifestyle choices

7. Nitrates

8. Some Diseases Can Spread from One
Person to Another
Infectious disease
Pathogen invades the body and multiplies
Transmissible disease
Infectious disease transmitted between people
Flu, tuberculosis, measles
Since 1950, death from infectious diseases have declined due to
Better health care
Better sanitation
Antibiotics
Vaccines

9. Infectious Diseases Are Still Major
Health Threats
Infectious diseases spread through
Air
Water
Food
Body fluids
Epidemics and pandemics

10. Science: Pathways for Infectious Diseases in Humans
Fig. 17-3, p. 439

11. Major Causes of Death from Infectious Diseases in the World, 2007
Fig. 17-4, p. 439

12. Genetic Resistance to Antibiotics Is
Increasing
Bacteria: rapid reproduction, easily spread
Overuse of antibiotics
Overuse of pesticides

13. Genetic Resistance to Antibiotics Is
Increasing
Methicillin-resistant Staphylococcus aureus
(MRSA)
Resistant to most antibiotics
Symptoms of MRSA
How will it be controlled?

14. The Growing Global Threat from
Tuberculosis
One in ten will become sick with TB
1.8 million deaths each year, primarily in less- developed countries
Why is tuberculosis on the rise?
Not enough screening and control programs
Genetic resistance to a majority of effective antibiotics
Person-to-person contact has increased
AIDS individuals are very susceptible to TB

15. Lung Tissue Destroyed by Tuberculosis
Fig. 17-5, p. 440

16. Viral Diseases Kill Large
Numbers of People
Influenza or flu virus
#1 Killer
HIV
#2 Killer
Hepatitis B virus (HBV)
#3 Killer
Emergent diseases: West Nile virus

17. Viral Diseases Kill Large
Numbers of People
Viruses that move form animals to humans
West Nile virus
Ecological medicine
Reduce chances of infection:
1.Wash your hands 2.Avoid touching your face 3.Avoid sick people

18. Ecological Medicine: How Humans Get Infectious Diseases from Animals
Human practices that encourage the spread of
diseases from animals to humans
Emerging infections
HIV
Avian flu
Hepatitis B
Lyme virus

19. Global HIV/AIDS Epidemic
Acquired immune deficiency syndrome (AIDS)
caused by human immunodeficiency virus (HIV)
Many secondary infections
No vaccine to prevent or cure AIDS
Expensive drugs—live longer

20. Global HIV/AIDS Epidemic
25 million deaths, so far
#1 killer globally of women 15-49
Most prevalent in sub-Saharan Africa
Life expectancy dropped from 62 to 47
Alters age structure of population

21. Malaria — The Spread of a Deadly
Parasite
Malaria
Caused by Plasmodium sp. carried by Anopheles
mosquitoes
Tropical and subtropical regions
Spread
Symptoms
Malarial cycle

22. Malaria — The Spread of a Deadly
Parasite
Malaria on the rise since 1970
Drug resistant Plasmodium
Insecticide resistant
mosquitoes
Clearing of tropical forests
AIDS patients particularly vulnerable

23. Global Outlook: Distribution of Malaria
Fig. 17-6, p. 444

24. A Boy in Brazil’s Amazon Sleeps Under an Insecticide-
Treated Mosquito Net
Fig. 17-7, p. 445

25. We Can Reduce the Incidence of
Infectious Diseases
Good news
Vaccinations on the rise
Oral rehydration therapy
Bad news
More money needed for medical research in
developing countries

26. Solutions: Infectious Diseases
Fig. 17-8, p. 445

27. Some Chemicals Can Cause Cancers,
Mutations, and Birth Defects
Toxic chemicals
Carcinogens
Chemicals, types of radiation, or certain viruses the
cause or promote cancer
Mutagens
Chemicals or radiation that cause mutations or increase
their frequency
Teratogens
Chemicals that cause harm or birth defects to a fetus or
embryo

28. PCBs Are Everywhere—A Legacy from
the Past
Class of chlorine-containing compounds
Very stable
Nonflammable
Break down slowly in the environment
Travel long distances in the air
Fat soluble
Biomagnification
Food chains and webs
Banned, but found everywhere

29. Potential Pathways on Which Toxic Chemicals
Move Through the Environment
Fig. 17-9, p. 447

30. Some Chemicals May Affect Our
Immune and Nervous Systems
Some natural and synthetic chemicals in the
environment can weaken and harm
Immune system
Nervous system
Neurotoxins: PCBs, arsenic, lead, some pesticides
Endocrine system

31. Mercury’s Toxic Effects Hg: teratogen and potent neurotoxin
Once airborne, persistent and not degradable
1/3 from natural sources
2/3 from human activities
Enters the food chain: biomagnification
How are humans exposed?
Inhalation: vaporized Hg or particulates
Eating fish with high levels of methylmercury
Eating high-fructose corn syrup

32. Mercury’s Toxic Effects Effects of Hg on humans Who is most at risk?
Damage nervous system, kidneys, lungs
Harm fetuses and cause birth defects
Who is most at risk?
Pregnant women
75% of exposure comes from eating fish

33. Solutions: Mercury Pollution
Fig , p. 449

34. Some Chemicals Affect the Human
Endocrine System
Glands that release hormones that regulate bodily systems and control sexual reproduction, growth, development, learning, behavior
Hormonally active agents have similar shapes and bind to hormone receptors
Gender benders
Thyroid disruptors
BPA?
Phthalates in plastics

35. Hormones and Hormones Mimics or Blockers
Fig , p. 449

36. Many Factors Determine the Harmful
Health Effects of a Chemical
Toxicology
Toxicity dependent on
Dose
Age
Genetic makeup
Multiple chemical sensitivity (MCS)
Solubility
Persistence
Biomagnification

37. Many Factors Determine the Harmful
Health Effects of a Chemical
Response
Acute effect: immediate or rapid
Chronic effect: permanent or long-lasting

38. Science: Estimating Human Exposure to Chemicals and Measuring Their Effects
Fig , p. 452

39. Protecting Children from Toxic
Chemicals
Analysis of umbilical cord blood: significance
Infants and children more susceptible
Eat, drink water, and breathe more per unit of body
weight than adults
Put their fingers in their mouths
Less well-developed immune systems and body
detoxification processes
Fetal exposure may increase risk of autism, asthma, learning disorders

40. Scientists Use Live Lab Animals and Non-animal
Tests to Estimate Toxicity
Mice and rats
Systems are similar to humans
Small, and reproduce rapidly
Is extrapolation to humans valid?
Dose-response curve: median lethal dose
(LD50)
Nonthreshold dose-response model
Threshold dose-response model

41. Scientists Use Live Lab Animals and Non-animal
Tests to Estimate Toxicity
More humane methods using animals
Replace animals with other models
Computer simulations
Tissue culture and individual animal cells
Chicken egg membranes
What are the effects of mixtures of potentially toxic chemicals?

42. Hypothetical Dose-Response Curve Showing Determination of the LD50
Fig , p. 453

43. Toxicity Ratings and Average Lethal Doses for Humans
Table 17-1, p. 453

44. Science: Two Types of Dose-Response Curves
Fig , p. 454

45. There Are Other Ways to Estimate the
Harmful Effects of Chemicals
Case reports and epidemiological studies
Limitations of epidemiological studies
Too few people tested
Length of time
Can you link the result with the chemical?
Cannot be used for new hazards

46. Are Trace Levels of Toxic Chemicals
Harmful?
Insufficient data for most chemicals
We are all exposed to toxic chemicals
Are the dangers increasing or are the tests just more sensitive?

47. Some Potentially Harmful Chemicals Found in Most Homes
Fig , p. 455

48. Why Do We Know So Little about the
Harmful Effects of Chemicals?
Severe limitations estimating toxicity levels
and risks
Only 2% of 100,000 chemicals have been adequately tested
99.5% of chemicals used in the United States are not supervised by government

49. Pollution Prevention and the
Precautionary Principle
Those introducing a new chemical or new technology would
have to follow new strategies
A new product is considered harmful until it can be proved to be safe
Existing chemicals and technologies that appear to cause
significant harm must be removed
2000: global treaty to ban or phase out the dirty dozen persistent organic pollutants (POPs)
2007 REACH program in the European Union

50. The Greatest Health Risks Come from
Poverty, Gender, and Lifestyle Choices
Risk analysis
Risk assessment
Risk management
Risk communication
Greatest health risks
Poverty
Gender
Lifestyle choices

51. Global Outlook: Number of Deaths per
Year in the World from Various Causes
Fig , p. 458

52. Comparison of Risks People Face in Terms of Shorter Average Life Span
Fig , p. 459

53. Death from Smoking Most preventable major cause of suffering and
premature death
Premature death of 5.4 million per year globally and
442,000 in the United States
Could be linked to increased dementia and Alzheimer’s disease
Nicotine: addictive
Effects of passive smoking (secondhand smoke)

54. Case Study: Death from Smoking
How to reduce smoking
Taxes
Classify and regulate nicotine
Bans on smoking in public places
Education

55. Normal Lung and Emphysema Lung
Fig , p. 459

56. Annual Deaths in the U.S. from Tobacco Use and Other Causes
Fig , p. 460

57. Most People Do a Poor Job of
Evaluating Risks
Fear
Degree of control
Whether a risk is catastrophic or chronic
Optimism bias
Want instant gratification without thinking of future harm

58. The Probability of Suffering Harm from Various Hazards
Cause of Death Heart Disease Cancer
Stroke
Accidental Injury
Motor Vehicle Accident* Intentional Self-harm (suicide) Falling Down Assault by Firearm
Fire or Smoke
Natural Forces (heat, cold, storms, quakes, etc.)
Electrocution* Drowning
Air Travel Accident*
Flood* (included also in Natural Forces above) Legal Execution
Tornado* (included also in Natural Forces above) Lightning Strike (included also in Natural Forces above) Snake, Bee or other Venomous Bite or Sting* Earthquake (included also in Natural Forces above) Dog Attack
Asteroid Impact* Tsunami*
Fireworks Discharge
Lifetime Odds 1-in-5
1-in-7 1-in-23
1-in-36
1-in-100
1-in-121
1-in-246
1-in-325
1-in-1,116
1-in-3,357
1-in-5,000
1-in-8,942
1-in-20,000
1-in-30,000
1-in-58,618
1-in-60,000
1-in-83,930
1-in-100,000
1-in-131,890
1-in-147,717
1-in-200,000**
1-in-500,000
1-in-615,488

59. Several Principles Can Help Us to
Evaluate and Reduce Risk
Compare risks
Determine how much you are willing to
accept
Determine the actual risk involved
Concentrate on evaluating and carefully
making important lifestyle choices

60. Three Big Ideas
We face significant hazards from infectious diseases, malaria, and tuberculosis, and from exposure to chemicals that can cause cancers and birth defects, and disrupt the human immune, nervous, and endocrine systems.
Because of the difficulty in evaluating the harm caused by exposure to chemicals, many health scientists call for much greater emphasis on pollution prevention.

61. Three Big Ideas
3. Becoming informed, thinking critically about risks, and making careful choices can reduce the major risks we face.