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CHAPTER
9
Environmental Health
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.
Objectives
• List the types of environmental health hazards
• Compare and contrast epidemiology and toxicology
• Describe the reasons why individuals respond
differently to the same environmental risks
• Discuss risk assessment.
Lesson 9.1 An Overview of Environmental Health
Types of Environmental
Health Hazards
• Biological: Viruses, bacteria, and
other organisms that cause
diseases (ex: Flu, pet dander)
• Social: Lifestyle choices that
endanger health (ex: smoking)
• Chemical: Harmful artificial and
natural chemicals in the
environment (ex: disinfectants)
• Physical: Natural disasters and
ongoing natural phenomena, such
as UV radiation, that can cause
health problems (Ex: earthquake)
Lesson 9.1 An Overview of Environmental Health
Epidemiology (Biological
Environmental Hazard)
• 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
Toxicology (Chemical
Environmental Hazard)
• 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.
Dose-Response Relationship
• Dose – the amount of substance an organism is exposed
to. Includes:
• Concentration of substance
• Time of exposure
• Response – effect an organism shows as a result of
exposure
• Examples:
• Exposure to radiation in high doses can result in death
• Exposure to radiation in low doses can result in illness
• Threshold dose – level of dosage that must be met to
bring about a response
Determining Dose-Response
Relationships
• Hard to determine in humans
because:
• Most people are accidentally
exposed to a hazard which is
then difficult to determine the
dose
• People are exposed to different
environmental hazards daily
• Scientists test effects of
hazard on animals which
makes it easier to control
dosage
Lesson 9.1 An Overview of Environmental Health
Individual Responses
• Sensitivity to hazards varies
with age, sex, weight, and
immune system health.
• A person’s genes and
environment affect chances
of suffering from a disease
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.
Tuberculosis-causing
bacteria
Objectives
• Describe how infectious diseases are spread
• Explain why emerging diseases are important to
monitor and control
• Differentiate between social hazards that are lifestyle
choices and those that cannot be controlled
Lesson 9.2 Biological and Social Hazards
Infectious Diseases
• Caused by pathogens (virus,
bacteria)
• 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.
Infectious Diseases
• Human to Human: HIV spread through blood and
bodily fluids, TB spread through coughing, sneezing,
speaking, spitting
• Water or Food: Cholera is spread through
contaminated water
• Other Organisms: spread by “vectors” who do not
suffer from the disease themselves; example is ticks
and mosquitoes
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
antibiotic
resistance, and
environmental
changes
Emerging Diseases
• Example is H1N1
• Pandemic – an outbreak that becomes widespread
and affects a whole region, continent, or world.
• Increasing mobility – when people move around the
Earth, they may be taking pathogens with them
• Antibiotic Resistance – disease becomes resistant to
our medicines through natural selection
• A Changing Environment – when people cut down
forests, they come in contact with new pathogens;
climate change allows spread of disease into new,
formerly cooler areas
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.
Objectives Revisited
• Describe how infectious diseases are spread
• Explain why emerging diseases are important to
monitor and control
• Differentiate between social hazards that are lifestyle
choices and those that cannot be controlled
Lesson 9.3 Toxic Substances in the
Environment
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.”
Objectives
• Explain what makes chemicals hazardous
• Discuss how chemical hazards affect human health
• List some indoor chemical hazards
• Discuss where chemical hazards can be found in the
environment
• Describe biomagnifications
Lesson 9.3 Toxic Substances in the Environment
Chemical Hazards
• Any chemical can be harmful in large enough amounts,
even water
• 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.
• Poison Ivy is a chemical
hazard but not a pollutant
Oil Pollution
Lesson 9.3 Toxic Substances in the Environment
Types of Chemical Hazards
• Carcinogens: Cancer-causing chemicals
• Chemical mutagens: Chemicals that
cause genetic mutations
• Teratogens: Chemicals that harm
embryos and fetuses
• Neurotoxins: Chemicals that affect the
nervous system (lead, mercury, pesticides)
• Endocrine disruptors: Chemicals that
interfere with the endocrine system
(hormones)
• Allergens: Chemicals that over-activate
the immune system (Asthma)
Dust mite protein is a common
allergen.
Lesson 9.3 Toxic Substances in the Environment
Indoor Chemical Hazards
Indoor Chemical Hazards
• Asbestos –
• used widely in insulation
• when disturbed releases fibers into the air, fibers can be
inhaled and lodged in lung tissue causing lung cancer
• Radon –
•
•
•
•
colorless, odorless, highly toxic radioactive gas
Made and released naturally when uranium decays
Can cause lung cancer
We live in an area with high radon potential
• Volatile Organic Compounds (VOCs)
• Released into air from plastic, perfume, pesticide
• Usually level of human exposure is low
Indoor Chemical Hazards
• Carbon Monoxide
• Colorless and odorless gas
• Unvented stoves, car exhaust, cigarette smoke
• Can cause headaches, dizziness, nausea, fatigue, death
• Lead –
• In air, drinking water (lead pipes), soil, paint, dust, etc.
• Causes damage to brain, liver, kidneys, stomach, learning
problems, behavior abnormalities, anemia, hearing loss,
death
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
pesticides
• Wind can carry chemicals far
away from their original
location
• Pesticide drift – airborne
transport of pesticides
A leaking oil line
Sources of Outdoor Chemical
Hazards
• In the ground:
• Pesticide use, improper disposal of electronics, etc.
• Humans can inhale them, absorb them by touching
contaminated soil, or ingest them through produce
• In the water: Chemical runoff from land or direct
drainage of toxic substances into water
• Amphibians are a good indicator of water quality
• Contaminants in streams and rivers can seep into drinking
water
Lesson 9.3 Toxic Substances in the Environment
Bioaccumulation and
Biomagnification
• Bioaccumulation: The buildup of
toxic substances in the bodies of
organisms
• Biomagnification: The increased
concentration of toxic substances
with each step in a food chain
• Persistent organic pollutants
(POPs) are biomagnified and stay in
the environment for long periods of
time and over long distances.
• Example: DDT
Objectives Revisited
• Explain what makes chemicals hazardous
• Discuss how chemical hazards affect human health
• List some indoor chemical hazards
• Discuss where chemical hazards can be found in the
environment
• Describe biomagnifications
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
Objectives
• Discuss how earthquakes affect structures on Earth’s
surface
• Discuss how volcanoes affect human lives and
property
• Describe tornadoes, hurricanes, and thunderstorms
• Discuss the dangers of avalanches
Lesson 9.4 Natural Disasters
Earthquakes
• 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
boundaries.
• Earthquakes can damage
structures and trigger
landslides and tsunamis.
Earthquakes: Surface Effects
• Can cause ground to sink and soil to liquefy
• Landslide – occur when rock and soil slide down a
slope
• Tsunami – large ocean wave that results from an
earthquake at the bottom of the ocean
Lesson 9.4 Natural Disasters
Volcanoes
• 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
Storms
• 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
Avalanches
• Masses of snow that slide down a slope
• Conditions favoring avalanches:
•
•
•
•
Slope greater than 30 degrees
Unstable snowpack (hard snow on top of weak snow)
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.
Objectives Revisited
• Discuss how earthquakes affect structures on Earth’s
surface
• Discuss how volcanoes affect human lives and
property
• Describe tornadoes, hurricanes, and thunderstorms
• Discuss the dangers of avalanches