Transcript Chapter 18 - AP Environmental Science

Chapter 18
Environmental Hazards
and Human Health
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Core Case Study: The Global
HIV/AIDS Epidemic
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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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Video: Aids Conference in Brazil
PLAY
VIDEO
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From ABC News, Environmental Science in the Headlines, 2005 DVD.3
Animation: HIV Replication
PLAY
ANIMATION
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Core Case Study: The Global
HIV/AIDS Epidemic
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Projected age structure of Botswana's
population in 2020.
AIDS has reduced the
life expectancy of subSaharan Africa from
62 to 47 years – 40
years in the seven
countries most
severely affected by
AIDS.
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Figure 18-2
Core Case Study: The Global
HIV/AIDS Epidemic
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The virus itself is not deadly, but it cripples
the immune system, leaving the body
susceptible to infections such as Kaposi’s
sarcoma (above).
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Figure 18-1
RISKS AND HAZARDS
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Risk is a measure of the likelihood that you
will suffer harm from a hazard.
We can suffer from:
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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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Video: Germs in Pakistan
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VIDEO
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From ABC News, Human Biology in the Headlines, 2006 DVD.
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BIOLOGICAL HAZARDS:
DISEASE IN DEVELOPED AND
DEVELOPING COUNTRIES
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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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Video: Polio Scare
PLAY
VIDEO
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From ABC News, Environmental Science in the Headlines, 2005 DVD.10
Transmissible Disease
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Pathway for infectious disease in humans.
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Figure 18-4
Transmissible Disease
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WHO estimates
that each year the
world’s seven
deadliest infections
kill 13.6 million
people – most of
them the poor in
developing
countries.
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Figure 18-5
Case Study: Growing Germ
Resistance to Antibiotics
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Rabidly producing infectious bacteria are
becoming genetically resistant to widely
used antibiotics due to:
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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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Video: The Problem with Pork
PLAY
VIDEO
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From ABC News, Environmental Science in the Headlines, 2005 DVD.14
Case Study: The Growing Global
Threat from Tuberculosis
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The highly infectious tuberculosis (TB) kills
1.7 million people per year and could kill 25
million people 2020.
Recent increases in TB are due to:
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Lack of TB screening and control programs
especially in developing countries due to expenses.
Genetic resistance to the most effective antibiotics.
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Viral Diseases
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Flu, HIV, and hepatitis B viruses infect and
kill many more people each year then
highly publicized West Nile and SARS
viruses.
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The influenza virus is the biggest killer virus
worldwide.
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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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Video: Bird Flu
PLAY
VIDEO
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From ABC News, Environmental Science in the Headlines, 2005 DVD.17
Video: Mask of Technology
PLAY
VIDEO
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From ABC News, Human Biology in the Headlines, 2006 DVD.
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Viral Diseases
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HIV is the second biggest killer virus worldwide.
Five major priorities to slow the spread of the
disease are:
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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
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Malaria kills
about 2 million
people per year
and has
probably killed
more than all of
the wars ever
fought.
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Figure 18-7
Case Study:
Malaria – Death by Mosquito
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Economists estimate that spending $2-3
billion on malaria treatment may save more
than 1 million lives per year.
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Figure 18-6
Case Study:
Malaria – Death by Mosquito
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Spraying insides of homes with low
concentrations of the pesticide DDT greatly
reduces the number of malaria cases.
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Under international treaty enacted in 2002, DDT
is being phased out in developing countries.
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Animation: Life Cycle of
Plasmodium
PLAY
ANIMATION
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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
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Fig. 18-8, p. 424
Ecological Medicine and
Infectious Diseases
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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
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A toxic chemical can cause temporary or
permanent harm or death.
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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
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A hazardous chemical can harm humans or
other animals because it:
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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
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Long-term exposure to some chemicals at
low doses may disrupt the body’s:
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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
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Molecules of certain synthetic chemicals have
shapes similar to those of natural hormones and
can adversely affect the endocrine system.
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Figure 18-9
Case Study:
A Black Day in Bhopal, India
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The world’s worst industrial accident occurred in
1984 at a pesticide plant in Bhopal, India.
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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
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Factors determining the harm caused by
exposure to a chemical include:
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The amount of exposure (dose).
The frequency of exposure.
The person who is exposed.
The effectiveness of the body’s detoxification
systems.
One’s genetic makeup.
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TOXICOLOGY: ASSESSING
CHEMICAL HAZARDS
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Typical
variations in
sensitivity to a
toxic chemical
within a
population,
mostly because
of genetic
variation.
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Figure 18-10
TOXICOLOGY: ASSESSING
CHEMICAL HAZARDS
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Estimating human
exposure to
chemicals and
their effects is very
difficult because of
the many and
often poorly
understood
variables involved.
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Figure 18-11
TOXICOLOGY: ASSESSING
CHEMICAL HAZARDS
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Children are more susceptible to the
effects of toxic substances because:
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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
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Under existing laws, most chemicals are
considered innocent until proven guilty,
and estimating their toxicity is difficult,
uncertain, and expensive.
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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
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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.
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TOXICOLOGY: ASSESSING
CHEMICAL HAZARDS
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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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RISK ANALYSIS
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Scientists have
developed ways to
evaluate and
compare risks, decide
how much risk is
acceptable, and find
affordable ways to
reduce it.
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Figure 18-12
RISK ANALYSIS
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Estimating risks from using many technologies
is difficult due to unpredictability of human
behavior, chance, and sabotage.
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Reliability of a system is multiplicative:
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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
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Annual deaths in the U.S. from tobacco
use and other causes in 2003.
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Figure 18-A
RISK ANALYSIS
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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.
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Figure 18-13
Perceiving Risk
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Most individuals evaluate the relative risk
they face based on:
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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
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Comparisons of
risks people
face expressed
in terms of
shorter average
life span.
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Figure 18-14
Becoming Better at Risk Analysis
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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.
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Figure 18-3