1. Chapter 17 Environmental Hazards & Human Health

2. 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.

3. What is a hazard? Anything that can cause
Injury, disease, death to humans
Damage to personal or public property
Deterioration or destruction of environment

4. Risks Are Usually Expressed as Probabilities
Probability of suffering harm from a hazard
Probability vs. Possibility
Risk Assessment
Process of using statistics to estimate how much harm a particular substance can cause to human health or environment
Risk Management
How to reduce risk (to what level and cost)
Risk = probability of suffering harm from a hazard usually mathematical – example 1 in 250 or percentage 30%

5. Risk Assessment & Management

6. Leading Global Risk Factors

7. Types of Hazards Biological:
Pathogen: an organism that causes disease in other organisms (bacteria, viruses, parasites, protozoa)

8. Types of Hazards 2. Chemical
In air, water soil, food, and human-made products

9. Types of Hazards 3. Physical
Earthquakes, floods, tornadoes, fire solar radiation

10. Types of Hazards 4. Cultural Smoking Working conditions Diet Drugs
Drinking
Assault
Unsafe sex
Poverty

11. Biological Hazards
The most serious biological hazards we fade are infectious diseases
Flu
AIDS
tuberculosis
diarrheal diseases
malaria.

12. Some Diseases Can Spread from One Person to Another
Infectious disease
Pathogen invades the body and multiplies
Transmissible disease
Contagious or communicable disease
Infectious disease transmitted between people
Flu, tuberculosis, measles
Transmissible = type of infectious. Nontransmissible – develop slowly not spread – heart disease

13. Some Diseases Can Spread from One Person to Another
Nontransmissible disease
Not caused by living organisms
Heart disease, most cancers, diabetes
Since 1950, death from infectious diseases have declined due to
Better health care
Better sanitation
Antibiotics
Vaccines
As age suffer from nontransmissible

14. Infectious Diseases Are Still Major Health Threats
Infectious diseases spread through
Air
Water
Food
Body fluids
Resistance of bacteria and insects to drugs and pesticides
Epidemic = Large Scale Outbreak
Pandemic =Global Epidemic
Epidemic = large scale outbreak
Global epidemic = pandemic
Infectious disease and genetic resistance

15. 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

16. Major Causes of Death from Infectious Diseases in the World, 2007

17. Three College Students Have Saved Thousands of Lives
North Carolina State seniors
Developed a device that can detect TB bacteria on a slide – glowing bacteria!
Very useful in less-developed countries
Pg 441

18. 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
Oral rehydration = fluid replacement as a treatment for dehydration – drink water mixed with salt and sugar and continue to eat

19. What Types of Chemical Hazards Do We Face?

20. Toxic Chemicals Carcinogens Mutagens Teratogens
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

21. How Can Chemicals Affect Humans?
Some natural and synthetic chemicals in the environment can weaken and harm
Immune system
Nervous system
Neurotoxins: PCBs, arsenic, lead, some pesticides
Endocrine system
Endocrine: Glands that release hormones that regulate bodily systems and control sexual reproduction, growth, development, learning, behavior

22. Hormones and Hormones Mimics or Blockers
Hormonally active agents have similar shapes and bind to hormone receptors
Figure 17.11: Hormones are molecules that act as messengers in the endocrine system to regulate various bodily processes, including reproduction, growth, and development. Each type of hormone has a unique molecular shape that allows it to attach to specially shaped receptors on the surface of, or inside, cells and to transmit its chemical message (left). Molecules of certain pesticides and other synthetic chemicals have shapes similar to those of natural hormones, allowing them to attach to the hormone molecules and disrupt the endocrine system in people and various other animals. These molecules are called hormonally active agents (HAAs). Because of the difficulty in determining the harmful effects of long-term exposure to low levels of HAAs, there is uncertainty about their effects on human health.
Fig , p. 449

23. How Can We Evaluate and Deal with Chemical Hazards?
Scientists use
live laboratory animals
case reports of poisonings
epidemiological studies
to estimate the toxicity of chemicals, but these methods have limitations.
Pollution prevention to reduce exposure to potentially harmful chemicals.

24. Many Factors Determine the Harmful Health Effects of a Chemical
Toxicology – study of harmful effects of chemicals on humans & other organisms
Toxicity – measure of harmfulness of substance.
Dependent on:
Dose
Age
Genetic makeup
Multiple chemical sensitivity (MCS)
Solubility
Persistence
Bio magnification
Toxi

25. Many Factors Determine the Harmful Health Effects of a Chemical
Persistence
Chemical’s resistance to breakdown
Response
Acute effect: immediate or rapid
Chronic effect: permanent or long-lasting

26. Estimating Human Exposure to Chemicals and Measuring Their Effects

27. Scientists Use Live Lab Animals and Nonanimal Tests to Estimate Toxicity
Dose-response curve: median lethal dose (LD50)
- Acutely lethal to 50% of animals tested (14 days)
Nonthreshold dose-response model
Threshold dose-response model
Nonthreshold = any dosage of toxic chemical causes harm that increases with dosage.
Threshold = certain level of the chemical must be reached before any detectable harmful

28. 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

29. Precautionary Principle
With significant uncertainty about potential serious harm from chemicals or technologies, decision makers act to prevent harm to humans and the environment
2000: global treaty to ban or phase out the dirty dozen persistent organic pollutants (POPs)
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

30. Health Risks Risk analysis Greatest health risks Risk assessment
Risk management
Risk communication
Greatest health risks
Poverty
Gender
Lifestyle choices

31. 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

32. 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

33. 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

34. Estimating Risks from Technologies Is Not Easy
System reliability (%) = Technological reliability (%) x Human reliability (%)
To err is human...
Example:
95% Technology x 75% Human =
71% System Reliability

35. 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

36. 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
Willing to accept = most people = 1 in 100,000 for env. hazards