Transcript Chapter 17 PowerPoint Notes

Chapter 17
Human Health and
Environmental Risks
Human Health and
Environmental Risks
Human are exposed to:
 Biological hazards
‒ from more than 1,400 pathogens
 Chemical hazards
‒ in air, water, soil, and food
 Physical hazards
‒ fire, earthquake, volcanic eruption…
 Cultural hazards
‒ smoking, poor diet, unsafe sex, drugs,
unsafe working conditions, and poverty
 Lifestyle choices
‒ smoking, overeating, alcohol/drug abuse
Module
56
Human Diseases
Learning Objectives
After this module, you should be able to:
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identify the different types of human diseases.
understand the risk factors for human chronic diseases.
discuss the historically important human diseases.
identify the major emergent infectious diseases.
discuss the future challenges for improving human health.
There are different types of
human diseases

Sources of biological hazards include bacteria,
viruses, insects, plants, birds, animals, and humans.
‒

These sources can cause a variety of health effects
ranging from skin irritation and allergies to infections,
cancer, and so on.
Disease: Any impaired function of the body with a
characteristic set of symptoms.
 This symbol is generally used as a warning, so that those potentially
exposed to the substances will know to take precautions.
There are different types of
human diseases
 Infectious disease – caused by living organisms
such as bacteria and viruses (also called contagious
or communicable disease) and can be spread from
person to person
‒
Transmissible: malaria, HIV,
tuberculosis, measles, influenza
 Noninfectious disease – NOT caused by pathogens
and cannot spread from person to person
‒ Non-transmissible: heart disease, cancer, asthma, diabetes
There are different types of
human diseases
 Acute disease: A disease that rapidly impairs the
functioning of an organism.
 Chronic disease: A disease that slowly impairs the
functioning of an organism.
 Can you name
some examples
of each??
Types of Human Diseases
 Among the world’s deaths caused by infectious
diseases, 94% are caused by only six types of
diseases.
Types of Human Diseases
 The World Health Organization (WHO) estimates that the
world’s seven deadliest infections kill 12.5 million people
a year (34,200/day).
̶ Most of these deaths
are poor people in
developing countries
̶ Most deaths are
preventable
Chronic Risk Factors in Humans
 For low-income countries, risks include issues related to
low nutrition and poor sanitation.
 For high-income countries, risks include issues related to
tobacco use, inactivity, obesity, and urban air pollution.
Some infectious diseases have
been historically important
 Environmental scientists are especially interested
in diseases that have environmental causes –
those caused by pathogens such as fungi,
bacteria, and viruses.
̶
Pathogens have evolved
a wide variety of ways to
infect humans.
Some infectious diseases have
been historically important
 Epidemic – a rapid, large scale outbreak of an
infectious disease in an area or a country
 Pandemic – an epidemic over a LARGE area like a
whole continent or even the globe
 Since 1950, death from infectious diseases have
declined due to:
‒ Better health care
‒ Antibiotics
‒ Vaccines
Historic Disease
 These diseases have killed hundreds of millions of
people throughout history:
‒ Plague: An infectious disease caused by a bacterium
(Yersinia pestis) that is carried by fleas.
‒ Malaria: An infectious disease caused by one of
several species of protists in the genus Plasmodium.
‒ Tuberculosis: A highly contagious disease caused by
the bacterium Mycobacterium tuberculosis that
primarily infects the lungs.
 For the most part, these diseases are no longer a
problem in the most-developed countries, but continue
to be an issue in low- and mid-income countries.
Case Study: Malaria
 Malaria
‒ Caused by Plasmodium sp. carried by Anopheles
mosquitoes
‒ It infects and destroys red blood cells, intense fever,
abdominal pains, vomiting, headaches
 Malaria on the rise since 1970
‒ Drug resistant Plasmodium
‒ Insecticide resistant mosquitoes
‒ Effect of global warming
‒ AIDS patients particularly vulnerable
Emergent Infectious Diseases

Many historic diseases are caused by bacteria or
protists and can, therefore, be treated with antibiotics.

Viruses are not treatable with antibiotics.
‒
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.
New diseases can emerge as pathogens mutate and
jump to infecting humans.
As a result increased movement of people and cargo,
diseases can now travel exceptionally fast.
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Could spread around the globe in 24 hours…
Emergent Infectious Diseases
 Emergent infectious disease: An infectious disease
that has not been previously described or has not
been common for at least 20 years.
Since the 1970s, new diseases, or diseases that have been rare
for more than 20 years, have been appearing throughout the
world at a rate of approximately one per year.
Emergent Infectious Diseases

Acquired Immune Deficiency Syndrome (AIDS)
‒
An infectious disease caused by the Human
Immunodeficiency Virus (HIV) that attacks the body’s
immune system making a person vulnerable to other
diseases and/or pathogens.
Ebola: A virus that causes hemorrhaging (uncontrolled
bleeding) with high death rates (50-90%).
 Mad cow disease: A disease in which prions mutate
into deadly pathogens and slowly damage a cow’s
nervous system.
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It is possible for humans to contract it from eating meat
from infected cattle.
Emergent Infectious Diseases
 Swine flu: A type of flu caused by the H1N1 virus.
‒
The Spanish Flu of 1918 that killed 100 million people
 Bird flu: A type of flu caused by the H5N1 virus.
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Usual response is to kill large numbers of birds (poultry
like chickens, ducks, turkeys, etc.)
 Severe acute respiratory syndrome (SARS): A
type of flu caused by a coronavirus.
 West Nile virus: A virus
that lives in hundreds of
species of birds and is
transmitted by mosquitoes.
Case Study: AIDS
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Acquired immune deficiency syndrome (AIDS)
caused by human immunodeficiency virus (HIV)
is the second biggest killer virus worldwide.
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Kills 2.1 million people a year (25 million so far)
2.5 million newly infected people a year
Virus itself doesn’t kill you
•
•
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Weakened immune system
Killed by a secondary infection
No vaccine to prevent or cure AIDS
•
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Expensive, anti-viral drugs
Live longer
Solutions:
Ways to Prevent or Reduce Disease
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Low-income countries need
improvements in nutrition,
wider availability of clean
drinking water, and proper
sanitation.
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High-income countries need
to promote healthier lifestyle
choices such as increased
physical activity, a balanced
diet, and limiting excess
food consumption and
tobacco use.
Module
57
Toxicology and
Chemical Risks
Learning Objectives
After this module, you should be able to:
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identify the major types of harmful chemicals.
explain how scientists determine the concentrations of chemicals
that harm organisms.
Many types of chemicals
can harm organisms
A toxic chemical can cause temporary or
permanent harm or death.
 A hazardous chemical is a chemical that is
flammable, explosive, or one that irritates the eyes,
skin or lungs.

 Chemical hazard labels indicate specific risks
̶
Scale from 0 (no risk) to 4 (highest risk)
Many types of chemicals
can harm organisms

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
nervous system
‒ Endocrine system: complex network of glands that
release minute amounts of hormones into the bloodstream
Chemicals that Harm Organisms
 Neurotoxin: A chemical that interferes with the
nervous system and disturbs brain functioning.
‒ lead, mercury, poisons from various insects/animals
 Carcinogen: Chemicals that cause or promote cancer.
‒ asbestos, radon, benzene, vinyl chloride, PCB’s
‒ Mutagen: chemicals that cause or increase the frequency
of mutations (changes) in DNA.
 Teratogen: A chemical that interferes with the normal
development of embryos or fetuses causing harm or
birth defects.
‒ ethyl alcohol, lead, mercury, phthalates, thalidomide
Chemicals that Harm Organisms
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Allergen: A chemical that causes allergic reactions by
causing an abnormally strong immune response.
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many chemicals in food, bee stings, penicillin
Endocrine disruptor: A chemical that mimics the
body’s natural hormones to disrupt metabolism,
growth, and reproduction.
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Hormonally active agents include: hormone blockers,
thyroid disrupters, gender benders
DDT, atrazine,
pharmaceutical
drugs
Many types of chemicals
can harm organisms
Scientists can determine the concentrations
of chemicals that harm organisms.

To assess the risk of a chemical, we need to know
concentrations that cause harm.
There are three ways to determine the harmful
concentration of a chemical:
 Dose response studies
 Prospective studies
 Retrospective studies
Dose Response Studies
 Dose-response study: exposing organisms (usually
mice or rats) to different amounts of a chemical and
observing the response (mortality or changes in
behavior or reproduction).
‒ LD50: The lethal dose that kills 50% of the individuals.
‒ LC50: The lethal concentration that kills 50% of the
individuals tested.
‒ ED50: The effective dose that causes 50% of the
individuals to display a harmful, but nonlethal, effects.
Dose Response Studies
 Dose-response curve: plotting the toxicity of a test
chemical on certain organisms.
 This information can be used to determine safe levels
for human exposure.
̶ Usually expressed as an amount/kg of body mass
Retrospective versus
Prospective Studies
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Retrospective study: A study that monitors people
who have been exposed to an environmental hazard
at some time in the past.
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Looking into the past
Compare accidental exposures to people who have not
been exposed.
Prospective study: A study that monitors people
who might become exposed to harmful chemicals in
the future.
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Looking into the future
Tract people’s exposures to predict health effects
CHALLENGING
Case Study: 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.
Factors that Determine Chemical Exposure
and the Harm Organisms Experience
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There are MANY factors that affect the chemical
concentrations that organisms experience and the
amount of harm that can be caused:
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Dose – the amount of a substance that has been
inhaled, ingested, or absorbed
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High dosage, low dosage
Toxicity – how harmful the chemical is
 Frequency of exposure – how often does it occur
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Frequent, infrequent
Length of exposure – how long the exposure lasts
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Short-term, long-term
Factors that Determine Chemical Exposure
and the Harm Organisms Experience
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Route of exposure: The
way in which an individual
might come into contact
with an environmental
hazard.
̶ Most chemicals have a
limited number of routes.

Not all routes of exposure
are equal:
̶ Making contact with skin is
not a bad as inhaling or or
ingesting it.
Factors that Determine Chemical Exposure
and the Harm Organisms Experience
 Age is an important factor…very young and/or very
old are much more at risk.
 One’s genetic makeup also
influences one’s sensitivity
to a toxic chemical.
 A related factor is how well the body’s
detoxification system (liver, kidneys lungs) works.
Factors that Determine Chemical Exposure
and the Harm Organisms Experience
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Certain chemical interactions can either increase or
decrease the harmful effects of a toxin:
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Antagonistic interaction – certain vitamins or
minerals can reduce the harm done by some kinds
of toxic chemicals
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Synergistic interaction – certain chemicals can
increase the negative effects of other chemicals
‒
The two chemicals together can be worse than either one
of them separately
Factors that Determine Chemical Exposure
and the Harm Organisms Experience
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The movement of a chemical in the environment and
the harm it can cause depends, in part, on its solubility.
Solubility: How well a chemical dissolves in a liquid.
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Water-soluble – Chemical that can move throughout our
environment, water supply, and living organisms (but can
be expelled rather quickly)
Fat-soluble – Chemicals that can penetrate our body’s
membranes and can be stored for long periods of time in
our tissues. They are not very
soluble in water and are found
in higher concentrations in soil.
Factors that Determine Chemical Exposure
and the Harm Organisms Experience
When a chemical is fat-soluble two other situations
may arise:
 Bioaccumulation – the tendency to be absorbed
and stored within certain tissues or organs
• Low concentrations over long periods of time can become
high levels in particular tissues
 Biomagnification – the accumulation of chemicals
as they pass through the food chain
• Organisms at the top of the food chain have higher levels
of toxins in their tissues
Factors that Determine Chemical Exposure
and the Harm Organisms Experience
The initial amount of chemical very low.
However, the combination of bioaccumulation
at each trophic level and upward movement
by consumption allows the concentration to
magnify to the point where it can be greatly
concentrated in the top predator.
Factors that Determine Chemical Exposure
and the Harm Organisms Experience
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Persistence: A chemical’s resistance to be broken
down. In other words, how long does it stay in an
active for in the environment.
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The longer it takes to
break down, the more
harm it can cause
Estimating Human Exposure to
Chemicals and Measuring Their Effects

Estimating human
exposure to chemicals
and their effects is
very difficult because
of the many and often
poorly understood
variables involved.
Harmful Health Effects of Chemicals

Response – the type and amount of health damage
done by exposure to toxic chemicals
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Acute exposure – short duration or single event exposure
Chronic exposure – repeated, or continuous exposure
over extended periods of time (or a lifetime)
Acute response – an immediate, rapid, and reversible
response to exposure that is usually brief and low dosage
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dizziness, coughing, vomiting, irritated eyes
Chronic response – a permanent or long lasting
consequence from an exposure that is either high dosage
or long-term
•
kidney or liver damage, damage to central nervous system,
cancer, or death
Case Study:
Protecting Children from Toxic Chemicals
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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.
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They are exposed to toxins when they put their fingers
or other objects in their mouths.
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Children usually have less well-developed immune
systems and detoxification processes than adults.
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Children’s bodies are still developing (especially the
nervous system) and are more susceptible to damage
done by chemicals.
Module
58
Risk Analysis
Learning Objectives
After this module, you should be able to:
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explain the processes of qualitative versus quantitative risk
assessment.
understand how to determine the amount of risk that can be
tolerated.
discuss how risk management balances potential harm against
other factors.
contrast the innocent-until-proven-guilty principle and the
precautionary principle.
Risk assessment estimates
potential harm
 Environmental hazard: Anything in the environment
that can potentially cause harm.
 Risk – a measure of the likelihood that you will suffer
harm from a hazard (something that has the potential
to cause harm)
̶ Possibility – it COULD happen
̶ Probability – how likely it is to happen

Risk analysis involves risk assessment, risk
acceptance, and risk management.
Qualitative vs. Quantitative
Risk Assessment
In a qualitative assessment, we make judgments
that are based on our perceptions but that are not
based on actual data and often do not match the
actual risk.
 Most individuals evaluate the 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.
Qualitative vs. Quantitative
Risk Assessment
A quantitative assessment uses actual data.
 Risk = probability of being exposed to a hazard X
probability of being harmed if exposed

Number of Deaths per
Year in the World from
Various Causes
Red numbers show deaths in terms of
the number of fully loaded 200-passenger
jumbo jets crashing every day of the year
with no survivors.
Qualitative vs. Quantitative
Risk Assessment

Some people are
willing to live with risk
and others are not.

Scientists,
economists, and
others can help us
weigh options as
objectively as
possible by
providing accurate
estimates of costs
and benefits.
Philosophies of Risk Management

Chemicals are regulated one of two philosophies:
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Innocent-until-proven-guilty principle: Requires that
scientific data definitively demonstrates harm before the
chemical is restricted or banned.
•
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Only about 10% of chemicals have been thoroughly screened
for toxicity, most of them in a retrospective manner.
Precautionary principle: Requires that when there is
scientific evidence that demonstrates a plausible risk, the
chemical must then be further tested to demonstrate it is
safe before it can continue to be used.
•
Manufacturers contend that wide-spread application of the
precautionary principle would make it too expensive to
introduce new chemicals and technologies.
Philosophies of Risk Management
“Toxicologists know a great deal about a few chemicals,
a little about many, and next to nothing about most.”
International Agreements on
Hazardous Chemicals

Stockholm Convention: A 2001 agreement among
127 nations concerning banning or sharply restricting
the use of 12 highly toxic chemicals known as
persistent organic pollutants (POPs.
“The Dirty Dozen.”