Transcript Chapter 18 - Loyola Blakefield

Chapter 18
Environmental Hazards
and Human Health
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.
What’s the Risk?
Risk assessment – scientific
process of estimating how
much harm a particular
hazard can cause to human
health or the environment.
 Risk management –
deciding whether or how to
reduce a particular risk to a
certain level and at what
cost
 Scientists have developed
ways to evaluate and
compare risks, decide how
much risk is acceptable,
and find affordable ways to
reduce it.

Figure 18-3
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.
RISK ANALYSIS
Identify hazards and
evaluate their risk
 Comparative risk
analysis
 Determine options
for reducing and/or
eliminating risks
 Risk communication

Figure 18-12
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%.
RISK ANALYSIS

Annual deaths in the U.S. from tobacco
use and other causes in 2003.
Figure 18-A
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
RISK
ANALYSIS

Comparisons of
risks people
face expressed
in terms of
shorter average
life span.
Figure 18-14
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)
Transmissible Disease

Pathway for infectious disease in humans.
Figure 18-4
Transmissible Disease

The World Health
Organization (WHO)
estimates that each
year the world’s
seven deadliest
infections kill 13.6
million people – most
of them the poor in
developing countries.
Figure 18-5
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.
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 by 2020.
 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.
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.
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.
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.

Core Case Study: The Global
HIV/AIDS Epidemic

Projected age structure
of Botswana's population
in 2020.
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.
Figure 18-2
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
Kaposi’s sarcoma (above).
Figure 18-1
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
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
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.
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
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.
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

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.
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
Case Study:
A Black Day in Bhopal, India

The world’s 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.
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.
TOXICOLOGY: ASSESSING
CHEMICAL HAZARDS

Typical
variations in
sensitivity to a
toxic chemical
within a
population,
mostly because
of genetic
variation.
Figure 18-10
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
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

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.
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.

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.

Female mosquito
bites infected human,
ingesting blood that
contains Plasmodium
gametocytes
Merozoites enter
blood-stream
and develop into
gametocytes
causing malaria
and making
infected person
a new reservoir
Plasmodium
develops in
mosquito
Sporozoites
penetrate liver
and develop into
merozoites
Female mosquito injects
Plasmodium sporozoites
into human host
Stepped Art
Fig. 18-7, p. 423