Environmental Hazards and Human Health

1
Chapter 18

• Environmental Hazards and Human Health

2
Chapter 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?

3
Core Case Study The Global HIV/AIDS Epidemic

• World Health Organization (WHO)
• 2009 claimed 1.8 million lives, down from 2006
  peak of 2.1 million.
• Has killed a total of over 25 million people
• No vaccine for HIV
• Most untreated people infected with HIV-1,
  eventually develop AIDS.
• Drugs help some infected people live longer, but
  only a tiny fraction can afford them.

4
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 some countries most severely affected
  by AIDS.
• Retards economic growth and increases poverty

Projected age structure of Botswana's population
in 2020.
Figure 18-2
5
HIV/AIDS

• Discovered in 1981
• Considered PANDEMIC by W.H.O.
• Transmitted in body fluids (blood, semen, vaginal
  fluid, pre-ejaculate or breast milk)
• Screening of blood has eliminated transmissions
  from transfusions
• Four major routes of transmission
• Unsafe sex, contaminated needles, breast milk,
  perinatal transmission

6
Animation HIV Replication
Animations/hiv_replication.html
7
Core Case Study The Global HIV/AIDS Epidemic

• The virus itself is not deadly, but it cripples
  the immune system, leaving the body susceptible
  to infections such as Kaposis sarcoma (above).

Figure 18-1
8
HIV/AIDS

• Reason it has continued to spread rampantly
• COMPLACENCY about risk
• It is not perceived as a risk, or individuals are
  not educated about the risk

9
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.

10
Video Germs in Pakistan
Videos/germs_in_pakistan.html

• From ABC News, Human Biology in the Headlines,
  2006 DVD.

11
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)

12
Video Polio Scare
Videos/polio_scare.html

• From ABC News, Environmental Science in the
  Headlines, 2005 DVD.

13
Transmissible Disease

• Pathway for infectious disease in humans.

Figure 18-4
14
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
15
Case Study Growing Germ Resistance to Antibiotics

• Rapidly 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.

16
Video The Problem with Pork
Videos/problem_with_pork.html

• From ABC News, Environmental Science in the
  Headlines, 2005 DVD.

17
Case Study The Growing Global Threat from
Tuberculosis

• The highly infectious tuberculosis (TB) kills 1.7
  million people per year and could kill 25 million
  people 2020.
• Attacks the lungs
• Spreads in the air when infected person coughs,
  sneezes or spits
• Most are asymptomatic (latent), 110 present, 50
  of those die when left untreated
• Recent increases in TB are due to
• Lack of TB screening and control programs
  especially in developing countries due to
  expenses.
• Genetic resistance to the most effective
  antibiotics.

18
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 major
  reservoirs of flu.
• Move from one species to another (zoonotic
  disease), mutations occur and exchange of genetic
  material with other viruses causes super bugs.

19
Video Bird Flu
Videos/bird_flu.html

• From ABC News, Environmental Science in the
  Headlines, 2005 DVD.

20
Video Mask of Technology
Videos/mask_of_technology.html

• From ABC News, Human Biology in the Headlines,
  2006 DVD.

21
Viral Diseases

• HIV second biggest killer virus worldwide.
• Five major priorities to slow the spread
• 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.

22
Case Study Malaria Death by Mosquito

• Malaria kills about 2 million people per year and
  has probably killed more than all of the wars
  ever fought.

Figure 18-7
23
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
24
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.

25

Solutions
Infectious Diseases
Increase research on tropical diseases and
vaccines
Reduce poverty
Decrease malnutrition
Improve drinking water quality
Reduce unnecessary use of antibiotics
Educate people to take all of an antibiotic
prescription
Reduce antibiotic use to promote livestock growth
Careful hand washing by all medical personnel
Immunize children against major viral diseases
Oral rehydration for diarrhea victims
Global campaign to reduce HIV/AIDS
Fig. 18-8, p. 424
26
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.

27
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.

28
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.

29
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.

30
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
31
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.

32
LOVE CANAL

• Niagara Falls, NY
• 21,000 tons of toxic waste buried beneath a
  neighborhood by HOOKER CHEMICAL
• Bordered by 2 bodies of water
• Area sold by company to the school board,
  detailing the hazards in the deed
• Company found negligent in waste disposal (site
  was 3x the size of the claim)
• Matter exposed by the press dioxin
• Effects 56 birth defects, cancer, retardation,
  nervous disorders, deafness, miscarriages,
  vegetation dying, odor pollution, basements
  coated in black

33
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.

34
TOXICOLOGY ASSESSING CHEMICAL HAZARDS

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

Figure 18-10
35
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.
• SYNERGISTIC EFFECTS

Figure 18-11
36
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.

37
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.

38
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 a risk 100 times that of adults.

39
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.

40
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
41
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.

42
RISK ANALYSIS

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

Figure 18-A
43
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
44
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.

45
RISK ANALYSIS

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

Figure 18-14
46
Becoming Better at Risk Analysis

• 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
47
THE STORY OF STUFF

• http//www.storyofstuff.com/