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Environmental Health
The Rise and Fall—and
Rise?—of DDT
• DDT is the least expensive way of killing the mosquitoes
that cause malaria.
• DDT harms fish and birds, and can cause liver damage,
cancer, and convulsions in humans.
• In the 1970s many countries banned the use of DDT, but
some African countries have resumed its use to control
Talk About It Evidence shows that DDT damages
ecosystems but helps eradicate malaria in areas
where millions of people die of the disease each
year. Should DDT be used in malaria-stricken areas?
Why or why not?
Lesson 9.1 An Overview of Environmental Health
One third of death and disease in the least
developed nations is a direct result of
environmental causes.
Lesson 9.1 An Overview of Environmental Health
Types of Environmental
Health Hazards
• Biological: Viruses, bacteria, and
other organisms that cause
• Social: Lifestyle choices that
endanger health
• Chemical: Harmful artificial and
natural chemicals in the
• Physical: Natural disasters and
ongoing natural phenomena, such
as UV radiation, that can cause
health problems
Lesson 9.1 An Overview of Environmental Health
• The study of disease in human
populations—how and where
they occur and how they can
be controlled
• Often involves studying large
groups over long periods
• Can determine statistical
associations between health
hazards and effects, but can’t
prove the hazards actually
caused the effects
Lesson 9.1 An Overview of Environmental Health
• The study of how poisonous
substances affect an
organism’s health
• Toxicity is a measure of how
harmful a substance is.
• Toxicologists look at toxicity
by determining doseresponse relationships.
Lesson 9.1 An Overview of Environmental Health
Individual Responses
• Sensitivity to hazards varies
with age, sex, weight, and
immune system health.
• Many diseases have
genetic as well as
environmental factors.
Did You Know? Thalidomide, a drug that
currently shows promise for treatment of
Alzheimer's, AIDS, and some cancers,
caused thousands of severe birth defects
when it was used as an anti-nauseal in
the 1950s and 60s.
Lesson 9.1 An Overview of Environmental Health
Risk Assessment
• Risk: The probability that a
hazard will cause harm
• Risk assessment: The
process of measuring risk
• Takes into account:
• The type of hazard
• How frequently humans will
be exposed to it
• How sensitive people are to it
Lesson 9.2 Biological and Social Hazards
Three quarters of infectious disease deaths
are caused by five types of diseases:
respiratory infections, AIDS, diarrheal
diseases, tuberculosis, and malaria.
Lesson 9.2 Biological and Social Hazards
Infectious Diseases
• Caused by pathogens
• Spread by human and animal
contact and through contaminated
food and water
• Cause of almost half of all deaths
in developing nations
• Covering your mouth when you
cough, washing your hands often,
and staying home from school if
you’re sick help prevent the
spread of infectious disease.
Did You Know? In 2002, AIDS killed
about 2 million people worldwide—
almost equal to the entire population
of Arkansas.
Lesson 9.2 Biological and Social Hazards
Emerging Diseases
• Diseases appearing in the human population for the first time
or suddenly beginning to spread rapidly
• Humans have little or no resistance, and no vaccines have
been developed.
• Facilitated by
increasing human
mobility, growing
resistance, and
Lesson 9.2 Biological and Social Hazards
Responding to Emerging Diseases
• World Health Organization (WHO):
Monitors health events worldwide and
coordinates international responses to
emerging diseases
• Centers for Disease Control and
Prevention (CDC): Responds to
emerging diseases in the United States;
the CDC developed pandemic plans to
deal with the spread of the H1N1 flu virus.
H1N1 Virus
Lesson 9.2 Biological and Social Hazards
Social Hazards
• Some social hazards are
easier to avoid than others.
• Examples of social hazards
include smoking, being
exposed to secondhand
smoke, living near an old
toxic waste site, working
with harmful chemicals, and
eating fatty foods.
Lesson 9.3 Toxic Substances in the
Chemicals are all around us, and
all of them can be harmful to our
health in large enough amounts.
In other words, “The dose makes
the poison.”
Lesson 9.3 Toxic Substances in the Environment
Chemical Hazards
• Any chemical can be harmful in large enough amounts.
• A pollutant is something released into the environment that
has some harmful impact on people and other organisms.
• Chemical hazards are not necessarily pollutants, and
pollutants are not necessarily chemical hazards.
Oil Pollution
Lesson 9.3 Toxic Substances in the Environment
Types of Chemical Hazards
• Carcinogens: Cancer-causing
• Chemical mutagens: Chemicals that
cause genetic mutations
• Teratogens: Chemicals that harm
embryos and fetuses
• Neurotoxins: Chemicals that affect the
nervous system
• Endocrine disruptors: Chemicals that
interfere with the endocrine system
Dust mite protein is a common
• Allergens: Chemicals that overactivate the immune system
Lesson 9.3 Toxic Substances in the Environment
Indoor Chemical Hazards
Lesson 9.3 Toxic Substances in the Environment
Sources of Outdoor Chemical Hazards
• In the air: Natural sources,
such as volcanic eruptions,
or human sources, such as
• In the ground: Pesticide
use, improper disposal of
electronics, etc.
• In the water: Chemical
runoff from land or direct
drainage of toxic
substances into water
A leaking oil line
Lesson 9.3 Toxic Substances in the Environment
Bioaccumulation and
• Bioaccumulation: The buildup of
toxic substances in the bodies of
• Biomagnification: The increased
concentration of toxic substances
with each step in a food chain
• Persistent organic pollutants are
biomagnified and stay in the
environment for long periods of time
and over long distances.
Lesson 9.4 Natural Disasters
Although we cannot prevent most natural
disasters, there are steps that scientists,
engineers, governments, and citizens can take
to resist damage and deal with the aftermath.
A landslide caused by the Great
Sichuan Earthquake in Sichuan
Province, China
Lesson 9.4 Natural Disasters
• Earth’s crust is broken into
large pieces called tectonic
plates, which float on a
layer of molten rock.
• Earthquakes tend to
occur along active plate
• Earthquakes can damage
structures and trigger
landslides and tsunamis.
Lesson 9.4 Natural Disasters
• Openings in Earth’s crust
that eject molten lava and
other materials
• Ash and gases from
volcanic eruptions can
block sunlight, causing
temperatures to drop.
• Eruptions can trigger
landslides and mudflows.
Did You Know? In 1991, Mount Pinatubo
erupted in the Philippines, covering the area
around the volcano with a layer of volcanic
materials up to 180 m (600 ft) thick.
• Molten lava can cover and
destroy surrounding land.
Lesson 9.4 Natural Disasters
• Tornadoes: Rotating
funnels of air that can travel
over 400 km (250 mi) per hr
• Hurricanes: Storms that
form over tropical oceans,
with winds over 119 km
(74 mi) per hour
• Thunderstorms: Produce
lightning and thunder,
usually with heavy rain
Did You Know? Hurricane Katrina, which struck
New Orleans in 2005, caused more than $80 billion
in damage and killed 1800 people.
Lesson 9.4 Natural Disasters
• Masses of snow that slide down a slope
• Conditions favoring avalanches:
Slope greater than 30 degrees
Unstable snowpack
Heavy snowfall
Warm temperatures
Did You Know? A big North
American avalanche can contain
230,000 m3 of snow—about the
equivalent of 20 football fields filled
with snow 3 m (10 ft) deep.