1. Environmental Hazards and Human Health17
Environmental Hazards and Human Health

2. Core Case Study: Mercury’s Toxic Effects
All mercury compounds are toxic
One third in the atmosphere comes from natural sources
Human activities provide the rest
Two main human exposures
Fish contaminated with mercury
Inhalation of vaporized mercury
Greatest risk is brain damage
Minimata Disease

3. Figure 17-1: Gloved hands hold a fish contaminated with mercury (left)
Figure 17-1: Gloved hands hold a fish contaminated with mercury (left). Fish are contaminated with mercury in many lakes, including this one in Wisconsin (right).
Fig. 17-1, p. 442

4. 17-1 What Major Health Hazards Do We Face?
We face health hazards from biological, chemical, physical, and cultural factors, and from the lifestyle choices we make

5. We Face Many Types of Hazards
Biological
Pathogen – an organism that causes disease in other organisms
Chemical
Harmful chemicals
Natural
Fire, earthquakes, volcanoes, etc.

6. Risks Are Usually Expressed as Probabilities
Probability of suffering harm from a hazard
Expressed as ratio or percentage
Risk assessment
Using statistical methods to estimate harm
Risk management
Deciding whether and how to reduce a particular risk

7. Risk Assessment Risk Management Comparative risk analysis
Hazard identification
Comparative risk analysis
What is the hazard?
How does it compare with other risks?
Risk reduction
How much should it be reduced?
Probability of risk
How likely is the event?
Risk reduction strategy
How will the risk be reduced?
Figure 17-2: Risk assessment and risk management are used to estimate the seriousness of various risks and to help reduce such risks. Question: What is an example of how you have applied this process in your daily living?
Consequences of risk
What is the likely damage?
Financial commitment
How much money should be spent?
Fig. 17-2, p. 443

8. We Face Many Types of Hazards (cont’d.)
Cultural
Unsafe working conditions, poverty, etc.
Lifestyle choices
Smoking, drinking too much alcohol, etc.

9. 17-2 What Types of Biological Hazards Do We Face?
The most serious biological hazards we face are infectious diseases such as flu, AIDS, tuberculosis, diarrheal diseases, and malaria

10. Some Diseases Can Spread from One Person to Another
Infectious disease
Pathogen invades the body and multiplies
Viruses, bacteria, parasites
Transmissible disease
Contagious or communicable disease
Infectious disease transmitted between people

11. Some Diseases Can Spread from One Person to Another (cont’d.)
Nontransmissible disease
Not caused by living organisms
Heart disease, most cancers, diabetes
Epidemic
Large-scale outbreak of an infectious disease
Pandemic – global

12. Pets
Livestock
Wild animals
Insects
Food
Water
Air
Fetus and babies
Other humans
Humans
Figure 17-3: There are a number of pathways by which infectious disease organisms can enter the human body. Question: Can you think of other pathways not shown here?
Stepped Art
© Cengage Learning 2015
Fig. 17-3, p. 444

13. Case Study: The Growing Global Threat from Tuberculosis
Many people have latent TB
1.4 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

14. Figure 17-5: The colorized red areas in this chest X-ray show where TB bacteria have destroyed lung tissue.
Fig. 17-5, p. 445

15. Figure 17-6: Estimated rates of occurrence of TB throughout the world in 2009.
Fig. 17-6, p. 446

16. Viral Diseases and Parasites Kill Large Numbers of People
Influenza or flu virus
Kills the most worldwide
HIV
Infects about 2.5 million people yearly
Emergent diseases – West Nile virus

17. Viral Diseases and Parasites Kill Large Numbers of People (cont’d.)
Viruses that move form animals to humans
West Nile virus
The new field of ecological medicine
Reduce chances of infection
Wash your hands
Avoid touching your face
Avoid sick people

18. Case Study: The 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

19. Case Study: The Global HIV/AIDS Epidemic (cont’d.)
30 million deaths between
Kills about 1.7 million people yearly
Most prevalent in sub-Saharan Africa
Life expectancy dropped from 62 to 47
Alters age structure of population

20. Case Study: Malaria – The Spread of a Deadly Parasite
Caused by parasite carried by certain mosquitoes
Tropical and subtropical regions
Spread
Uninfected mosquito bites infected person, later bites an uninfected person
Climate change – expected to spread malaria

21. Case Study: Malaria – The Spread of a Deadly Parasite (cont’d.)
Malaria is on the rise since 1970
Drug-resistant Plasmodium
Insecticide resistant mosquitoes
Clearing of tropical forests
AIDS patients particularly vulnerable
What is the focus of current malaria research?

22. Figure 17-7: Global outlook: About 47% of the world’s population live in areas in which malaria is prevalent.
© Cengage Learning 2015
Fig. 17.7, p. 451

23. Figure 17-8: This baby in Senegal, Africa, is sleeping under an insecticide-treated mosquito net to reduce the risk of being bitten by malaria-carrying mosquitoes.
© Cengage Learning 2015
Fig. 17.8, p. 452

24. We Can Reduce the Incidence of Infectious Diseases
Good news
Percentage of worldwide deaths resulting from infectious diseases
Dropped from 35% to 15% from 1970 to 2008
Vaccinations on the rise
Oral rehydration therapy
Bad news
More money needed for medical research in developing countries

25. Solutions Infectious Diseases
Increase research on tropical diseases and vaccines
Reduce poverty and malnutrition
Improve drinking water quality
Reduce unnecessary use of antibiotics
Sharply reduce use of antibiotics on livestock
Figure 17-9: There are a number of ways to prevent or reduce the incidence of infectious diseases, especially in less-developed countries. Questions: Which three of these approaches do you think are the most important? Why?
Immunize children against major viral diseases
Provide oral rehydration for diarrhea victims
Conduct global campaign to reduce HIV/AIDS
Fig. 17.9, p. 453

26. 17-3 What Types of Chemical Hazards Do We Face?
There is growing concern about chemicals in the environment that can cause cancers and birth defects, and disrupt the human immune, nervous, and endocrine systems

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. Case Study: 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
Ends up in food chains and webs
Banned, but found everywhere

29. Water table Fish Soil Water table
Atmosphere
Vegetation
Crops
Surface water
Humans
Animals
Surface water
Groundwater
Water table
Fish
Vegetation
Figure 17-10: PCBs and other persistent toxic chemicals can move through the living and nonliving environment by a number of pathways.
Soil
Groundwater
Water table
Rock
Rock
© Cengage Learning 2015
Fig , p. 454

30. Some Chemicals May Affect Our Immune and Nervous Systems
Some natural and synthetic chemicals in the environment can weaken and harm:
Immune system
Some chemicals weaken the immune system
Nervous system
Neurotoxins – PCBs, arsenic, lead, some pesticides
Example – Methylmercury
What are the effects of mercury poisoning?

31. Solutions Mercury Pollution Prevention Control
Phase out waste incineration
Sharply reduce mercury emissions from coal-burning plants and incinerators
Remove mercury from coal before it is burned
Label all products containing mercury
Figure 17-12: There are a number of ways to prevent or control inputs of mercury (Core Case Study) into the environment from human sources—mostly coal-burning power plants and incinerators. Questions: Which four of these solutions do you think are the most important? Why?
Switch from coal to natural gas and renewable energy resources
Collect and recycle batteries and other products containing mercury
Fig , p. 455

32. 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
Hormone mimics
Hormone blockers

33. Normal Hormone Process
Estrogen-like chemical
Antiandrogen chemical
Receptor
Cell
Figure 17-13: Each type of hormone has a unique molecular shape that allows it to attach to specially shaped receptors on the surface of, or the inside of, a cell and to transmit its chemical message (left). Molecules of certain pesticides and other synthetic chemicals, called hormonally active agents (HAAs, center and right), have shapes similar to those of natural hormones, allowing them to attach to the hormone molecules and disrupt the endocrine systems of humans and other animals.
Normal Hormone Process
Hormone Mimic
Hormone Blocker
© Cengage Learning 2015
Fig , p. 456

34. Figure 17-15: Individuals matter: You can reduce your exposure, and that of any children you care for, to hormone disrupters. Questions: Which three of these steps do you think are the most important ones to take? Why?
Fig , p. 458

35. 17-4 How Can We Evaluate Chemical Hazards?
Scientists use live laboratory animals, case reports of poisonings, and epidemiological studies to estimate the toxicity of chemicals, but these methods have limitations
Many health scientists call for much greater emphasis on pollution prevention to reduce our exposure to potentially harmful chemicals

36. Many Factors Determine the Harmful Health Effects of Chemicals
Toxicology – study of harmful effects
Dose
Age
Genetic makeup
Multiple chemical sensitivity (MCS)
Solubility
Persistence
Biomagnification

37. Many Factors Determine the Harmful Health Effects of Chemicals (cont’d
Response
Acute effect – immediate or rapid
Chronic effect – permanent or long-lasting

38. Scientific measurements and modeling
Water pollutant levels
Air pollutant levels
Soil/dust levels
Food pesticide levels
Nutritional health
Scientific measurements and modeling ?
Overall health
Lifestyle
Figure 17-16: Toxicology. 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: What are three of these factors that might make you more vulnerable to the harmful effects of chemicals?
Predicted level of toxicant in people
Personal habits
Metabolism
Genetic predisposition
Accumulation
Excretion
Lung, intestine,
and skin absorption rates
Fig , p. 459

39. Case Study: Protecting Children from Toxic Chemicals
Analysis of umbilical cord blood
180 chemicals found that cause cancers in humans or animals
Infants and children more susceptible
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
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 (cont’d.)
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. Percentage of population killed by a given dose
Figure 17-17: 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
Dose (hypothetical units)
Fig , p. 460

43. Nonlinear dose-response
Effect
Effect
Figure 17-18: Scientists use two types of dose-response curves to help them estimate the toxicity of various chemicals. The linear and nonlinear curves in the graph on the left apply if even the smallest dosage of a chemical has a harmful effect that increases with the dosage. The graph on the right applies if a harmful effect occurs only when the dosage exceeds a certain threshold level.
Threshold level
Dose
Dose
Nonthreshold
Threshold
Fig , p. 461

44. 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
Result linked to chemical
Cannot be used for new hazards

45. Are Trace Levels of Toxic Chemicals Harmful?
Insufficient data for most chemicals
We are all exposed to toxic chemicals
Trace amounts
Difference between increasing dangers and better testing

46. Chloroform
Source: Chlorine-treated water in
hot showers
Possible threat: Cancer
Para-dichlorobenzene
Source: Air fresheners,
mothball crystals
Threat: Cancer
Tetrachloroethylene
Source: Dry-cleaning
fluid fumes on clothes
Threat: Nerve disorders,
damage to liver and
kidneys, possible cancer
Formaldehyde
Source: Furniture stuffing,
paneling, particleboard,
foam insulation
Threat: Irritation of eyes,
throat, skin, and lungs;
nausea; dizziness
1,1,1-Trichloroethane
Source: Aerosol sprays
Threat: Dizziness,
irregular breathing
Styrene
Source: Carpets,
plastic products
Threat: Kidney and
liver damage
Nitrogen oxides
Source: Unvented gas
stoves and kerosene
heaters, woodstoves
Threat: Irritated lungs,
children's colds,
headaches
Carbon monoxide
Source: Faulty furnaces,
unvented gas stoves and
kerosene heaters,
woodstoves
Threat: Headaches,
drowsiness, irregular
heartbeat, death
Benzo-α-pyrene
Source: Tobacco smoke,
woodstoves
Threat: Lung cancer
Particulates
Source: Pollen, pet
dander, dust mites,
cooking smoke particles
Threat: Irritated lungs,
asthma attacks, itchy
eyes, runny nose,
lung disease
Tobacco smoke
Source: Cigarettes
Threat: Lung cancer, respiratory
ailments, heart disease
Radon-222
Source: Radioactive soil
and rock surrounding
foundation, water supply
Threat: Lung cancer
Asbestos
Source: Pipe insulation, vinyl
ceiling and floor tiles
Threat: Lung disease, lung cancer
Figure 17-19: A number of potentially harmful chemicals are found in many homes. 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?
Methylene chloride
Source: Paint strippers and thinners
Threat: Nerve disorders, diabetes
Stepped Art
Fig , p. 462

47. Why Do We Know So Little about the Harmful Effects of Chemicals?
There are severe limitations in 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

48. Why Do We Know So Little about the Harmful Effects of Chemicals
Why Do We Know So Little about the Harmful Effects of Chemicals? (cont’d.)
Precautionary principle
Those introducing a new chemical or new technology need 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

49. Case Study: Pollution Prevention Pays
The 3M Company
1975 to 2008, prevented more than 1.5 million tons of pollutants from reaching the environment
Employee reward program

50. 17-5 How Do We Perceive Risks and How Can We Avoid the Worst of Them?
We can reduce the major risks we face by becoming informed, thinking critically about risks, and making careful choices

51. The Greatest Health Risks Come from Poverty, Gender, and Lifestyle Choices
Greatest health risk by far
Malnutrition, increased infectious disease, unsafe drinking water
Gender
Being born male
Lifestyle choices
Overeating, smoking, etc.

52. Cause of death
Annual deaths
Poverty/malnutrition/ disease cycle
11 million (150)
Tobacco
6.0 million (82)
Pneumonia and flu
3.2 million (44)
Air pollution
3.2 million (44)
HIV/AIDS
1.7 million (23)
Diarrhea
1.6 million (22)
Tuberculosis
1.4 million (19)
Automobile accidents
1.2 million (16)
Work-related
injury and disease
Figure 17-20: Global outlook: Scientists have estimated the number of deaths per year in the world from various causes. Numbers in parentheses represent these death tolls in terms of numbers of fully loaded 200-passenger jet airplanes crashing every day of the year with no survivors. Question: Which three of these causes are the most threatening to you?
1.1 million (15)
Malaria
1.0 million (14)
Hepatitis B
655,000 (9)
Measles
139,000 (2)
Fig , p. 465

53. Number of people (% of world’s population)
Lack of access to
Number of people (% of world’s population)
Adequate
sanitation facilities
2.6 billion (37%)
Enough fuel for
heating and cooking
2 billion (28%)
Electricity
2 billion (28%)
Adequate health care
1.1 billion (15%)
Adequate housing
1 billion (14%)
Figure 17-21: These are some of the harmful effects that result from living in poverty. Questions: Which two of these effects would be the most harmful for you? Why?
Enough food for good health
925 million (13%)
Clean
drinking water
880 million (12%)
Fig , p. 466

54. Case Study: Death from Smoking
Most preventable major cause of suffering and premature death
Killed 100 million people during the 20th century
Could be linked to increased dementia and Alzheimer’s disease
Nicotine – additive
What are the effects of passive smoking (secondhand smoke) ?

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

56. Estimating Risks from Technologies Is Not Easy
Reliability
System reliability (%) = Technological reliability (%) x Human reliability (%)
Human reliability is much lower than technological reliability
Much harder to predict

57. Most People Do a Poor Job of Evaluating Risks
Five factors can cause misjudgments in risk:
Fear
Degree of control
Whether a risk is catastrophic or chronic
Optimism bias
Instant gratification

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

59. Three Big Ideas We face significant hazards from: Infectious diseases
Flu, AIDS, tuberculosis, diarrheal diseases, and malaria
Exposure to chemicals that can:
Cause cancers and birth defects,
Disrupt the human immune, nervous, and endocrine systems

60. Three Big Ideas (cont’d.)
Because of the difficulty of evaluating the harm caused by exposure to chemicals, many health scientists call for much greater emphasis on pollution prevention
By becoming informed, thinking critically about risks, and making careful choices, we can reduce the major risks we face

61. Tying It All Together: Mercury’s Toxic Effects and Sustainability
Mercury is highly toxic
We can reduce some threats
Shift to renewable sources of energy
Cutting resource use and wastes
Mimic biodiversity
Use diverse strategies for solving environmental and health problems