Download Ch. 17 Environmental Hazards and Human Health Notes

4/16/13
Environmental Hazards and
Human Health Notes
THE GLOBAL HIV/AIDS
EPIDEMIC
Chapter 17
•  According to the World Health
Organization (WHO), in 2008 about 33
million people worldwide (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.
The Global HIV/AIDS Epidemic
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.
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.
–  Natural hazards: such as fire, earthquake,
volcanic eruption…
–  Cultural hazards: such as smoking, poor
diet, drugs, unsafe working conditions, and
poverty.
•  The virus itself is not deadly, but it
cripples the immune system, leaving the
body susceptible to infections such as
Kaposi’s sarcoma.
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.
Transmissible Disease
•  WHO estimates
that each year the
world’s seven
deadliest
infections kill 11.3
million people –
most of them the
poor in developing
countries.
Growing Germ Resistance to
Antibiotics
The Growing Global Threat from
Tuberculosis
•  Rabidly producing infectious bacteria are
becoming genetically resistant to widely
used antibiotics due to:
•  The highly infectious tuberculosis (TB) kills
1.8 million people per year and could kill
25 million people 2020.
•  Recent increases in TB are 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.
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.
–  Lack of TB screening and control programs
especially in developing countries due to
expenses.
–  Genetic resistance to the most effective
antibiotics.
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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Malaria – Death by Mosquito
•  Malaria kills
about 2 million
people per year
and has
probably killed
more than all of
the wars ever
fought.
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.
Malaria – Death by Mosquito
•  Economists estimate that spending $2-3
billion on malaria treatment may save
more than 1 million lives per year.
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.
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.
Fig. 17-8, p. 445
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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.
Effects of Chemicals on the Immune,
Nervous, and Endocrine Systems
Effects of Chemicals on the
Immune, Nervous, and Endocrine
Systems
•  Long-term exposure to some chemicals at
low doses may disrupt the body’s:
–  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.
A Black Day in Bhopal, India
•  The world’s worst industrial accident
occurred in 1984 at a pesticide plant in
Bhopal, India.
•  Molecules of certain synthetic chemicals
have shapes similar to those of natural
hormones and can adversely affect the
endocrine system.
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 body’s detoxification
systems.
–  One’s genetic makeup.
–  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.
TOXICOLOGY: ASSESSING
CHEMICAL HAZARDS
•  Typical
variations in
sensitivity to a
toxic chemical
within a
population,
mostly because
of genetic
variation.
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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.
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.
TOXICOLOGY: ASSESSING
CHEMICAL HAZARDS
Protecting Children from Toxic
Chemicals
•  Under existing laws, most chemicals are
considered innocent until proven guilty,
and estimating their toxicity is difficult,
uncertain, and expensive.
•  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.
–  Federal and state governments do not
regulate about 99.5% of the commercially
used chemicals in the U.S.
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.
RISK ANALYSIS
•  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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RISK ANALYSIS
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%.
•  Annual deaths in the U.S. from tobacco
use and other causes in 2003.
Hazard
Perceiving Risk
Shortens average life span
in the United States by
Poverty
7–10 years
Born male
7.5 years
Smoking
6–10 years
Overweight (35%)
•  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.
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
Flu
AIDS
4 months
4 months
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
Living lifetime near nuclear
plant
RISK
ANALYSIS
•  Comparisons of
risks people
face expressed
in terms of
shorter average
life span.
10 hours
Fig. 17-17, p. 459
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.
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