1. Chapter 17 Environmental Hazards and Human Health

2. 17-1 What Major Health Hazards Do We Face?
Concept We face health hazards from biological, chemical, physical, and cultural factors, and from the lifestyle choices they make.

3. Human Chemical Exposure
We are exposed to numerous chemicals every day:
environmental sources such as air and water pollution
pesticides
cleaning products
food additives
Some of these chemicals are threats to human health, but tracing exposures and determining what levels of risk they pose is a painstaking process.
How do harmful substances enter the body, and how do they damage cells?
In this chapter, we learn how dangers are assessed, what kind of regulations we use to reduce exposures, and how we manage associated human health risks.

4. Science: Risk Assessment and Risk Management
Figure 17.2: Science.
Risk assessment and risk management are used to estimate the seriousness of various risks and how to reduce such risks. Question: What is an example of how you have applied this process in your daily living?
Risk assessment and risk management are used to estimate the seriousness of various risks and how to reduce such risks. Question: What is an example of how you have applied this process today?
Fig. 17-2, p. 437

5. We Face Many Types of Hazards
Biological:
Pathogens are organisms that causes disease in other organisms.
Chemical
Physical
Cultural
Lifestyle choices
Write down two examples of each.

6. 17-2 What Types of Biological Hazards Do We Face?
Concept The most serious biological hazards we fade are infectious diseases such as flu, AIDS, tuberculosis, diarrheal diseases, and malaria.

7. Some Diseases Can Spread from One Person to Another, Others Cannot
Infectious disease
Pathogen invades the body and multiplies
Transmissible disease
Contagious or communicable disease
Infectious disease transmitted between people
Flu, tuberculosis, measles
Nontransmissible disease
Not caused by living organisms
Heart disease, most cancers, diabetes
Which of these
are communicable?
HIV
Malaria
Asthma
Ebola
Flu

8. Vast Improvements…
Since 1950, death from infectious diseases have declined due to:
Better health care
Better sanitation
Antibiotics
Vaccines

9. However … Infectious Diseases Are Still Major Health Threats
Infectious diseases spread through:
Air
Water
Food
Body fluids
Epidemics and pandemics
Resistance of bacteria and insects to drugs and pesticides

10. Science: Pathways for Infectious Diseases in Humans
Figure 17.3: Science.
There are a number of pathways on which infectious disease organisms can enter the human body. Question: Can you think of other pathways not shown here?
Fig. 17-3, p. 439

11. Major Causes of Death (CDC, 2005)

12. From the Centers for Disease Control and Prevention (CDC) (Current)

13. What are the major causes of death from infectious diseases in the world?
Figure 17.4: Global outlook: The World Health Organization estimates that each year, the world’s seven deadliest infectious diseases kill 11.3 million people—most of them poor people in less-developed countries (Concept 17-2). This averages about 31,000 mostly preventable deaths every day—roughly the same as wiping out everyone in the U.S. states of Massachusetts and Alabama or all the people in Delhi, India, each year. Question: How many people, on average, die prematurely from these diseases every hour? (Data from the World Health Organization, 2007)

14. Major Causes of Death from Infectious Diseases in the World, 2007
Figure 17.4: Global outlook: The World Health Organization estimates that each year, the world’s seven deadliest infectious diseases kill 11.3 million people—most of them poor people in less-developed countries (Concept 17-2). This averages about 31,000 mostly preventable deaths every day—roughly the same as wiping out everyone in the U.S. states of Massachusetts and Alabama or all the people in Delhi, India, each year. Question: How many people, on average, die prematurely from these diseases every hour? (Data from the World Health Organization, 2007)
Fig. 17-4, p. 439

15. Current Event and W.H.O. Information Blitz
Homework (About 2 nights worth):
Readings for Harkness on Thursday, Ebola.
Active reading establishes your base score.
Prompt for discussion already written.
Read Core Case Study, p. 436; Science Focus, p. 442
Review Questions 2 and 3, p. 463
Reading as appropriate

16. Flu

17. Asthma

19. Case Study: Malaria — The Spread of a Deadly Parasite (1)
Caused by Plasmodium sp. carried by Anopheles mosquitoes
Tropical and subtropical regions
Africa
Central and South America
Southeast Asia

20. Case Study: Malaria — The Spread of a Deadly Parasite (2)
Malaria on the rise since 1970
Drug resistant Plasmodium
Insecticide resistant mosquitoes
Clearing of tropical forests
AIDS patients particularly vulnerable
Prevention of spread and current research
DDT effective against mosquitoes but banned in U.S.
DDT (dichlorodiphenyltrichloroethane) is a colorless, crystalline, tasteless and almost odorless organochloride known for its insecticidal properties.

21. Global Outlook: Distribution of Malaria
Figure 17.6: Global outlook: About 40% of the world’s population lives in areas in which malaria is prevalent. Malaria kills at least 1 million people a year or about 2 people every minute. More than 80% of these victims live in sub-Saharan Africa and most of them are children younger than age 5. According to the WHO, every 45 seconds, a child in Africa dies of malaria. (Data from the World Health Organization and U.S. Centers for Disease Control and Prevention)
Fig. 17-6, p. 444

23. Ebola

24. Science Focus: Genetic Resistance to Antibiotics Is Increasing (1)
Bacteria: rapid reproduction, easily spread
Overuse of antibiotics
Overuse of pesticides
Widespread use of pesticides or antibiotics eliminates the weaker individuals in a rapidly reproducing population.
This causes an increase in the frequency of individuals in the population who have genetic resistance to pesticides or antibiotics because they are the ones left to rapidly reproduce.

25. Case Study: 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

26. Lung Tissue Destroyed by Tuberculosis
Figure 17.5: The colorized red areas in this chest X-ray show where TB bacteria have destroyed lung tissue.
Fig. 17-5, p. 440

27. Science Focus (p. 442) Ecological Medicine: How Humans Get Infectious Diseases from Animals
Human practices that encourage the spread of diseases from animals to humans
Emerging infections
HIV
Ebola virus
Avian flu
Hepatitis B
Lyme virus

28. A Boy in Brazil’s Amazon Sleeps Under an Insecticide-Treated Mosquito Net
Figure 17.7: This boy, who lives in Brazil’s Amazon Basin, is sleeping under an insecticide-treated mosquito net to reduce his risk of being bitten by malaria-carrying mosquitoes. Such nets cost about $5 each and can be donated through groups such as
This boy, who lives in Brazil’s Amazon Basin, is sleeping under an insecticide-treated mosquito net
to reduce his risk of being bitten by malaria-carrying mosquitoes. Such nets cost about $5 each an
can be donated through groups such as
Fig. 17-7, p. 445

29. 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

30. Solutions: Infectious Diseases
Figure 17.8: There are a number of ways to prevent or reduce the incidence of infectious diseases, especially in less-developed countries. Question: Which three of these approaches do you think are the most important?
Fig. 17-8, p. 445

31. 17-3 What Types of Chemical Hazards Do We Face?
Concept There is growing concern about chemicals in the environment that can cause cancers and birth defects, and disrupt the human immune, nervous, and endocrine system.

32. 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

33. Top 5 Toxic Substances—Human and Environmental Health
Arsenic
Lead
Mercury
Vinyl chloride
Used to make PVC plastics
Polychlorinated biphenyls
PCBs

34. Case Study: PCBs Are Everywhere— A Legacy from the Past
Polychlorinated Biphenyl (PCB)--Class of chlorine-containing compounds
Very stable
Nonflammable
Break down slowly in the environment
Travel long distances in the air
Fat soluble
Bioaccumulation
Biomagnification
Food chains and webs
Banned, but found everywhere

35. Case Study: PCBs Are Everywhere— A Legacy from the Past
PCBs belong to a broad family of man-made organic chemicals known as chlorinated hydrocarbons. PCBs were domestically manufactured from 1929 until their manufacture was banned in 1979.
PCBs were used in hundreds of industrial and commercial applications including electrical, heat transfer, and hydraulic equipment; as plasticizers in paints, plastics, and rubber products; in pigments, dyes, and carbonless copy paper; and many other industrial applications.

36. PCBs
Once in the environment, PCBs do not readily break down and therefore may remain for long periods of time cycling between air, water, and soil. PCBs can be carried long distances and have been found in snow and sea water in areas far away from where they were released into the environment. As a consequence, PCBs are found all over the world.
PCBs can accumulate in the leaves and above-ground parts of plants and food crops. They are also taken up into the bodies of small organisms and fish. As a result, people who ingest fish may be exposed to PCBs that have bioaccumulated in the fish they are ingesting.
PCBs have been demonstrated to cause cancer, as well as a variety of other adverse health effects on the immune system, reproductive system, nervous system, and endocrine system.

37. Potential Pathways on Which Toxic Chemicals Move Through the Environment
Figure 17.9: PCBs and other persistent toxic chemicals can move through the living and nonliving environment on a number of pathways.
PCBs and other persistent toxic chemicals can move through th
living and nonliving environment on a number of pathways.
Fig. 17-9, p. 447

38. Bioaccumulation and Biomagnification
Bioaccumulation: Organisms that consume toxic materials that do not break down will eventually excrete or store these chemicals in their fatty tissues (fat soluble) over time; organisms can have a build up of toxins/chemicals.
Biomagnification: The increased concentration of toxins in the tissues of organisms that are in higher levels of the food web/chain.
Example: DDT (dichlorodiphenyltrichloroethane) is a colorless, crystalline, tasteless and almost odorless organochloride known for its insecticidal properties.
Found in tissues of different organisms within an aquatic ecosystem:
DDT in a water system ppm
Water is consumed by algae, and the toxin is concentrated to 0.04 ppm.
Algae are consumed by primary consumers—shrimp—and the toxin is concentrated to 0.16 ppm.
Shrimp are consumed by Secondary Consumers, eels, and the toxin is concentrated to 0.28 ppm.
Eels are consumed by the Tertiary Consumers, the ring-billed gull, and the toxin is concentrated to 75.5 ppm.

39. 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
Hormones

40. 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

41. Science Focus: Mercury’s Toxic Effects (1)
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
Under certain conditions in aquatic environments, bacteria can convert inorganic mercury compounds to highly toxic methylmercury, which can be biomagnified in food chains/ webs.
3. Eating high-fructose corn syrup??

42. Science Focus: Mercury’s Toxic Effects (2)
Effects of Hg on humans
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

43. Solutions: Mercury Pollution
Figure 17.10: There are a number of ways to prevent or control inputs of mercury into the environment from human sources—mostly coal-burning power plants and incinerators. Question: Which four of these solutions do you think are the most important?
Fig , p. 449

44. Superfund Act
Comprehensive Environmental Response, Compensation & Liability Act (CERCLA): Otherwise known as the Superfund Act- calls for a rapid cleanup of abandoned dumpsites containing toxic waste.

45. Video: Hazardous Chemicals in Urban Environments
Habitable Planet

46. 17-4 How Can We Evaluate and Deal with Chemical Hazards?
Concept 17-4A Scientists use live laboratory animals, case reports of poisonings, and epidemiological studies to estimate the toxicity of chemicals, but these methods have limitations.
Concept 17-4B Many health scientists call for much greater emphasis on pollution prevention to reduce our exposure to potentially harmful chemicals.

47. Many Factors Determine the Harmful Health Effects of a Chemical (1)
Toxicology
Toxicity dependent on
Dose
Age
Genetic makeup
Multiple chemical sensitivity (MCS)
Solubility
Persistence
Biomagnification

48. Many Factors Determine the Harmful Health Effects of a Chemical (2)
Response
Acute effect: immediate or rapid
Chronic effect: permanent or long-lasting

49. Science: Estimating Human Exposure to Chemicals and Measuring Their Effects
Figure 17.12: Science.
Estimating human exposure to chemicals and measuring the effects of that exposure are very difficult because of the many and often poorly understood variables involved. Question: Which of these factors, if any, might make you more vulnerable to the harmful effects of chemicals?
Fig , p. 452

50. Case Study: 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

51. Scientists Use Live Lab Animals and Nonanimal Tests to Estimate Toxicity (1)
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

52. Scientists Use Live Lab Animals and Nonanimal Tests to Estimate Toxicity (2)
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?

53. Hypothetical Dose-Response Curve Showing Determination of the LD50 (median lethal dose)
Figure 17.13: Science.
This hypothetical dose-response curve illustrates how scientists can estimate the LD50, the dosage of a specific chemical that kills 50% of the animals in a test group. Toxicologists use this method to compare the toxicities of different chemicals.
* LD50 is the dose required to be lethal for 50% of the test population.
Fig , p. 453

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

55. Science: Two Types of Dose-Response Curves
Figure 17.14: Science.
Scientist use two types of dose-response curves to help them estimate the toxicity of various chemicals. The linear and nonlinear curves in the left graph apply if even the smallest dosage of a chemical has a harmful effect that increases with the dosage. The curve on the right applies if a harmful effect occurs only when the dosage exceeds a certain threshold level. Which model is better for measuring the effects of a specific harmful agent is uncertain and controversial because of the difficulty in estimating the responses to very low dosages.
Fig , p. 454

56. 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

57. 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?

58. Some Potentially Harmful Chemicals Found in Most Homes
Figure 17.15: A number of potentially harmful chemicals are found in many homes. Most people have traces of these chemicals in their blood and body tissues. We do not know the long-term effects of exposure to low levels of such chemicals. (Data from U.S. Environmental Protection Agency, Centers for Disease Control and Prevention, and New York State Department of Health) Questions: Does the fact that we do not know much about the long-term harmful effects of these chemicals make you more likely or less likely to minimize your exposure to them? Why?
Fig , p. 455

59. 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

60. 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

61. Individuals Matter: Ray Turner and His Refrigerator
1974: Ozone layer being depleted by chlorofluorocarbons (CFCs)
1992: International agreement to phase out CFCs and other ozone-destroying chemicals
Ray Turner: citrus-based solvents to clean circuit boards

62. 17-5 How Do We Perceive Risks and How Can We Avoid the Worst of Them?
Concept We can reduce the major risks we face by becoming informed, thinking critically about risks, and making careful choices.

63. 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

64. Global Outlook: Number of Deaths per Year in the World from Various Causes
Figure 17.16: Global outlook: Scientists have estimated the number of deaths per year in the world from various causes. Numbers in parentheses represent death tolls in terms of the number of fully loaded 200-passenger jet airplanes crashing every day of the year with no survivors. Because of the lack of media coverage of the largest annual causes of death and its sensational coverage of other causes of death, most people are misinformed and guided by irrational fears about the comparative levels of risk. Question: Which three of these items are most likely to shorten your life span? (Data from World Health Organization, 2007)
Fig , p. 458

65. Comparison of Risks People Face in Terms of Shorter Average Life Span
Figure 17.17: Global outlook: This figure compares key risks that people can face, expressed in terms of an estimated shorter average life span (Concept 17-5). Excepting poverty and gender, the greatest risks people face come mostly from the lifestyle choices they make. These are merely generalized relative estimates. Individual responses to these risks differ because of factors such as genetic variation, family medical history, emotional makeup, stress, and social ties and support. Question: Which three of these factors are most likely to shorten your life span? (Data from Bernard L. Cohen)
Fig , p. 459

66. Case Study: Death from Smoking (1)
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: additive
Effects of passive smoking (secondhand smoke)

67. Case Study: Death from Smoking (2)
How to reduce smoking
Taxes
Classify and regulate nicotine
Bans on smoking in public places
Education

68. Normal Lung and Emphysema Lung
Figure 17.18: There is a startling difference between normal human lungs (left) and the lungs of a person who died of emphysema (right). The major cause is prolonged smoking and exposure to air pollutants.
Fig , p. 459

69. Annual Deaths in the U.S. from Tobacco Use and Other Causes
Figure 17.19: Smoking is by far the nation’s leading cause of preventable death, causing more premature deaths each year than all the other categories in this figure combined. (Data from U.S. National Center for Health Statistics, Centers for Disease Control and Prevention, and U.S. Surgeon General)
Fig , p. 460

70. 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

71. 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

72. 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.

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