Risk, Toxicology and Human Health

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Risk, Toxicology and Human Health

• Asim Zia
• Introduction to Environmental Issues
• EnvS 001, Spring 2007
• Department of Environmental Studies
• San Jose State University

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Chapter 18 Overview Questions

• What types of hazards do people face?
• What types of disease (biological hazards)
  threaten people in developing countries and
  developed countries?
• What chemical hazards do people face?
• How can risks be estimated and recognized?

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Core Case Study The Global HIV/AIDS Epidemic

• According to the World Health Organization (WHO),
  in 2005 about 42 million people worldwide (1.1
  million in the U.S.) were infected with HIV.
• There is no vaccine for HIV if you get AIDS,
  you will eventually die from it.
• Drugs help some infected people live longer, but
  only a tiny fraction can afford them.

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Core Case Study The Global HIV/AIDS Epidemic

• AIDS has reduced the life expectancy of
  sub-Saharan Africa from 62 to 47 years 40 years
  in the seven countries most severely affected by
  AIDS.

Projected age structure of Botswana's population
in 2020.
Figure 18-2
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RISKS AND HAZARDS

• Risk is a measure of the likelihood that you will
  suffer harm from a hazard.
• We can suffer from
• Biological hazards from more than 1,400
  pathogens.
• Chemical hazards in air, water, soil, and food.
• Physical hazards such as fire, earthquake,
  volcanic eruption
• Cultural hazards such as smoking, poor diet,
  unsafe sex, drugs, unsafe working conditions, and
  poverty.

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BIOLOGICAL HAZARDS DISEASE IN DEVELOPED AND
DEVELOPING COUNTRIES

• Diseases not caused by living organisms cannot
  spread from one person to another
  (nontransmissible disease), while those caused by
  living organisms such as bacteria and viruses can
  spread from person to person (transmissible or
  infectious)

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Transmissible Disease

• Pathway for infectious disease in humans.

Figure 18-4
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Transmissible Disease

• WHO estimates that each year the worlds seven
  deadliest infections kill 13.6 million people
  most of them the poor in developing countries.

Figure 18-5
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Case Study Growing Germ Resistance to Antibiotics

• Rabidly producing infectious bacteria are
  becoming genetically resistant to widely used
  antibiotics due to
• Genetic resistance Spread of bacteria around the
  globe by humans, overuse of pesticides which
  produce pesticide resistant insects that carry
  bacteria.
• Overuse of antibiotics A 2000 study found that
  half of the antibiotics used to treat humans were
  prescribed unnecessarily.

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Viral Diseases

• Flu, HIV, and hepatitis B viruses infect and kill
  many more people each year then highly publicized
  West Nile and SARS viruses.
• The influenza virus is the biggest killer virus
  worldwide.
• Pigs, chickens, ducks, and geese are the major
  reservoirs of flu. As they move from one species
  to another, they can mutate and exchange genetic
  material with other viruses.

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Viral Diseases

• HIV is the second biggest killer virus worldwide.
  Five major priorities to slow the spread of the
  disease are
• Quickly reduce the number of new infections to
  prevent further spread.
• Concentrate on groups in a society that are
  likely to spread the disease.
• Provide free HIV testing and pressure people to
  get tested.
• Implement educational programs.
• Provide free or low-cost drugs to slow disease
  progress.

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Case Study Malaria Death by Mosquito

• Economists estimate that spending 2-3 billion on
  malaria treatment may save more than 1 million
  lives per year.

Figure 18-6
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Case Study Malaria Death by Mosquito

• Spraying insides of homes with low concentrations
  of the pesticide DDT greatly reduces the number
  of malaria cases.
• Under international treaty enacted in 2002, DDT
  is being phased out in developing countries.

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Ecological Medicine and Infectious Diseases

• Mostly because of human activities, infectious
  diseases are moving at increasing rates from one
  animal species to another (including humans).
• Ecological (or conservation) medicine is devoted
  to tracking down these connections between
  wildlife and humans to determine ways to slow and
  prevent disease spread.

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CHEMICAL HAZARDS

• A toxic chemical can cause temporary or permanent
  harm or death.
• Mutagens are chemicals or forms of radiation that
  cause or increase the frequency of mutations in
  DNA.
• Teratogens are chemicals that cause harm or birth
  defects to a fetus or embryo.
• Carcinogens are chemicals or types of radiation
  that can cause or promote cancer.

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CHEMICAL HAZARDS

• A hazardous chemical can harm humans or other
  animals because it
• Is flammable
• Is explosive
• An irritant
• Interferes with oxygen uptake
• Induce allergic reactions.

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Effects of Chemicals on the Immune, Nervous, and
Endocrine Systems

• Long-term exposure to some chemicals at low doses
  may disrupt the bodys
• Immune system specialized cells and tissues that
  protect the body against disease and harmful
  substances.
• Nervous system brain, spinal cord, and
  peripheral nerves.
• Endocrine system complex network of glands that
  release minute amounts of hormones into the
  bloodstream.

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Effects of Chemicals on the Immune, Nervous, and
Endocrine Systems

• Molecules of certain synthetic chemicals have
  shapes similar to those of natural hormones and
  can adversely affect the endocrine system.

Figure 18-9
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Case Study A Black Day in Bhopal, India

• The worlds worst industrial accident occurred in
  1984 at a pesticide plant in Bhopal, India.
• An explosion at Union Carbide pesticide plant in
  an underground storage tank released a large
  quantity of highly toxic methyl isocyanate (MIC)
  gas.
• 15,000-22,000 people died
• Indian officials claim that simple upgrades could
  have prevented the tragedy.

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TOXICOLOGY ASSESSING CHEMICAL HAZARDS

• Factors determining the harm caused by exposure
  to a chemical include
• The amount of exposure (dose).
• The frequency of exposure.
• The person who is exposed.
• The effectiveness of the bodys detoxification
  systems.
• Ones genetic makeup.

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TOXICOLOGY ASSESSING CHEMICAL HAZARDS

• Typical variations in sensitivity to a toxic
  chemical within a population, mostly because of
  genetic variation.

Figure 18-10
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TOXICOLOGY ASSESSING CHEMICAL HAZARDS

• Estimating human exposure to chemicals and their
  effects is very difficult because of the many and
  often poorly understood variables involved.

Figure 18-11
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Water pollutant levels
Air pollutant levels
Soil/dust levels
Food pesticide levels
Nutritional health
?
Mathematical measurements modeling
Overall health
Lifestyle
Predicted level of toxicant in people
Personal habits
Metabolism
Genetic predisposition
Accumulation
Excretion
Lung, intestine skin absorption rates
Fig. 18-11, p. 431
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TOXICOLOGY ASSESSING CHEMICAL HAZARDS

• Children are more susceptible to the effects of
  toxic substances because
• Children breathe more air, drink more water, and
  eat more food per unit of body weight than
  adults.
• They are exposed to toxins when they put their
  fingers or other objects in their mouths.
• Children usually have less well-developed immune
  systems and detoxification processes than adults.

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TOXICOLOGY ASSESSING CHEMICAL HAZARDS

• Under existing laws, most chemicals are
  considered innocent until proven guilty, and
  estimating their toxicity is difficult,
  uncertain, and expensive.
• Federal and state governments do not regulate
  about 99.5 of the commercially used chemicals in
  the U.S.

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Protecting Children from Toxic Chemicals

• The U.S. Environmental Protection Agency proposed
  that regulators should assume children have 10
  times the exposure risk of adults to
  cancer-causing chemicals.
• Some health scientists contend that regulators
  should assume children at a risk 100 times that
  of adults.

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TOXICOLOGY ASSESSING CHEMICAL HAZARDS

• Some scientists and health officials say that
  preliminary but not conclusive evidence that a
  chemical causes significant harm should spur
  preventive action (precautionary principle).
• Manufacturers contend that wide-spread
  application of the precautionary principle would
  make it too expensive to introduce new chemicals
  and technologies.

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How Would You Vote?

• Should we rely more on the precautionary
  principle as a way to reduce the risks from
  chemicals and technologies?
• a. No. Assuming that every chemical or technology
  is a serious health or environmental threat will
  lead to wasteful over-regulation, high costs and
  hinder the development of critically needed
  pesticides, plastics, and other commercial
  products.
• b. Yes. Preventing the commercialization of
  harmful chemicals and technologies is better than
  dealing with the high costs of medical treatments
  and environmental damage.

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RISK ANALYSIS

• Scientists have developed ways to evaluate and
  compare risks, decide how much risk is
  acceptable, and find affordable ways to reduce it.

Figure 18-12
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Comparative Risk Analysis
Most Serious Ecological and Health Problems
High-Risk Health Problems Indoor air pollution
Outdoor air pollution Worker chemical
exposure Pollutants in drinking water
Pesticide residues on food Toxic chemicals in
consumer products
High-Risk Ecological Problems Global climate
change Stratospheric ozone depletion
Wildlife habitat alteration destruction
Species extinction, loss of biodiversity
Medium-Risk Ecological Problems Acid
deposition Pesticides Airborne toxic
chemicals Toxic chemicals, nutrients, and
sediment in surface waters
Low-Risk Ecological Problems Oil spills
Groundwater pollution Radioactive isotopes
Acid runoff to surface waters Thermal pollution
Fig. 18-12, p. 433
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RISK ANALYSIS

• Estimating risks from using many technologies is
  difficult due to unpredictability of human
  behavior, chance, and sabotage.
• Reliability of a system is multiplicative
• If a nuclear power plant is 95 reliable and
  human reliability is 75, then the overall
  reliability is (0.95 X 0.75 0.71) 71.

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RISK ANALYSIS

• Annual deaths in the U.S. from tobacco use and
  other causes in 2003.

Figure 18-A
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RISK ANALYSIS

• Number of deaths per year in the world from
  various causes. Parentheses show deaths in terms
  of the number of fully loaded 400-passenger jumbo
  jets crashing every day of the year with no
  survivors.

Figure 18-13
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Cause of death
Annual deaths
11 million (75)
Poverty/malnutrition/ disease cycle
5 million (34)
Tobacco
3.2 million (22)
Pneumonia and flu
3 million (21)
Air pollution
3 million (21)
HIV/AIDS
2 million (14)
Malaria
1.9 million (13)
Diarrhea
1.7 million (12)
Tuberculosis
1.2 million (8)
Car accidents
Work-related injury disease
1.1 million (8)
1 million (7)
Hepatitis B
800,000 (5)
Measles
Fig. 18-13, p. 435
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Perceiving Risk

• Most individuals evaluate the relative risk they
  face based on
• Degree of control.
• Fear of unknown.
• Whether we voluntarily take the risk.
• Whether risk is catastrophic.
• Unfair distribution of risk.
• Sometimes misleading information, denial, and
  irrational fears can cloud judgment.

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RISK ANALYSIS

• Comparisons of risks people face expressed in
  terms of shorter average life span.

Figure 18-14
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Shortens average life span in the U.S. by
Hazard
Poverty
710 years
Born male
7.5 years
Smoking
610 years
Overweight (35)
6 years
Unmarried
5 years
Overweight (15)
2 years
Spouse smoking
1 year
Driving
7 months
Air pollution
5 months
Alcohol
5 months
Drug abuse
4 months
Flu
4 months
AIDS
3 months
Drowning
1 month
Pesticides
1 month
Fire
1 month
Natural radiation
8 days
Medical X rays
5 days
Oral contraceptives
5 days
Toxic waste
4 days
Flying
1 day
Hurricanes, tornadoes
1 day
10 hours
Lifetime near nuclear plant
Fig. 18-14, p. 436
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Becoming Better at Managing Risk

• We can carefully evaluate or tune out of the
  barrage of bad news covered in the media, compare
  risks, and concentrate on reducing personal risks
  over which we have some control.

Figure 18-3