Transcript Chapter 17 Human Health and Environmental Risks

Chapter 17
Human Health and Environmental Risks
Human health is affected by a
large number of risk factors
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A disease is any impaired function of the body with a
characteristic set of symptoms.
Figure 17.1 shows the leading causes of death in the
world.
Human health is affected by a
large number of risk factors
Three major categories of risk that can harm
human health:
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physical
biological
chemical
Human health is affected by a
large number of risk factors
Physical Risks
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Physical risks include environmental factors, such
as natural disasters, that can cause injury and loss
of life.
Physical risks also include less dramatic factors
such as excessive exposure to ultraviolet radiation
from the sun.
Human health is affected by a
large number of risk factors
Biological risks are those associated with diseases.
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Infectious diseases- those caused by infectious agents,
known as pathogens. Examples: pneumonia and
venereal diseases
Chronic disease - slowly impairs the functioning of a
person’s body.
Acute disease - rapidly impairs the functioning of a
person’s body.
When a pathogen causes a rapid increase in disease, we
call it an epidemic. When an epidemic occurs over a
large geographic region such as an entire continent, we
call it a pandemic.
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Human health is affected by a
large number of risk factors
Figure 17.2 shows leading health risks in the world. If we consider all
deaths that occur and separate them into different causes, we can
examine which categories cause the highest percentage of all deaths. (a)
low income countries include issues related to low nutrition and poor
sanitation. (b) high income countries include issues related to tobacco,
inactivity, and obesity.
Historical Diseases
• Plague –also known as Black Death. Plague is caused by an
infection from a bacterium that is carried by fleas.
• Malaria – is caused by an infection from any one of several
species of protists in the genus Plasmodium. The parasite
spends one stage of its life inside a mosquito and another
stage of its life inside a human.
• Tuberculosis – is a highly contagious disease caused by a
bacterium that primarily infects the lungs. Tuberculosis is
spread when a person coughs and expels the bacteria into
the air.
Historical Diseases
• Figure 17.5 is an illustration of the Black Death in Europe.
As depicted in Carlo Coppola’s The Marketplace in Naples
During the Plague of 1656, plague pandemics repeatedly
swept through Europe from the 1300s through the 1800s,
and killed millions of people.
• Because the disease
caused black sores on
people’s bodies, it also
had the name Black
Death.
Emergent Infectious Diseases
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HIV/AIDS – In the late 1970s, rare types of pneumonia and
cancer began appearing in individuals with weakened
immune systems. The virus is spread though sexual contact
and sharing needles during drug use.
Ebola – first discovered in Republic of Congo near the Ebola
River. The virus has infected several hundred humans and
primates. It has killed a large percentage of those infected.
Mad Cow Disease – a disease in which a pathogen slowly
damages a cow’s nervous system. The cow loses coordination
of its body and then dies.
Emergent Infectious Diseases
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Bird Flu - Spanish flu was an avian influenza, also known as
bird flu. It is caused by the H1N1 virus. This virus is similar
to a flu virus that humans normally contract, but H1N1
normally infects only birds.
West Nile Virus – lives in hundreds of species of birds and is
transmitted among birds by mosquitoes. Although the virus
can be highly lethal to some species of birds most species of
birds survive the infection.
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Emergent Infectious Diseases
Figure 17.7 shows a map of the emergence of new diseases around the
world. 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.
Infectious diseases have killed large
numbers of people
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Figure 17.4 shows the
many pathways of
transmitting pathogens.
Pathogens have evolved a
wide variety of ways to
infect humans.
Toxicology is the study of
chemical risks
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Neurotoxins- chemicals that disrupt the nervous system
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Carcinogens- chemicals that cause cancer
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Teratogens- chemicals that interfere with the normal
development of embryos or fetuses
Allergens- chemicals that cause allergic reactions
Endocrine disruptors- chemicals that interfere with the
normal functioning of hormones in an animal’s body
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Toxicology is the study of
chemical risks
Figure 17.15 shows an endocrine disruption. Male animals normally
make estrogen and then convert it to testosterone, an important
hormone for male reproduction. Some endocrine disrupting
hormones are thought to interfere with this process, causing less
testosterone to be produced.
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can have low sperm
counts and eggs may
develop inside their
testes.
Dose-Response Studies
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Dose-response studies expose animals or plants to
different amounts of a chemical and then observe a
variety of possible responses including mortality or
changes in behavior or reproduction.
Acute studies are of a short duration, while chronic
studies are a longer duration.
LD50 - lethal dose that kills 50% of the individuals
ED50 - effective dose that causes 50% of the animals
to display the harmful but nonlethal effect
Dose-Response Studies
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Figure 17.16 shows an LD50 graph. To determine the dose of a chemical
that causes a 50 percent death rate, scientists expose animals to different
doses of a chemical and determine what proportion of the animals die at
each dose.
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experiment
typically
produces an
S-shaped curve.
Retrospective versus Prospective
Studies
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Epidemiology is a field of science that strives to
understand the causes of illness and disease in human
and wildlife populations.
Retrospective studies monitor people who have been
exposed to a chemical at some time in the past.
Prospective studies monitor people who might
become exposed to harmful chemicals in the future.
Synergistic interactions- when two risks come
together and cause more harm than one would. For
example, the health impact of a carcinogen such as
asbestos can be much higher if an individual also
smokes tobacco.
Retrospective versus Prospective
Studies
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Figure 17.19 discusses the chemical
disaster in Bhopal, India. (a) In 1984,
a massive release of methyl
isocyanate gas killed and injured
thousands of people. (b)
Retrospective studies that have
followed the survivors of the
accident have identified a large
number of longer-term health effects
from the accident.
Factors That Determine Concentrations
of Chemicals Organisms Experience
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Figure 17.20 shows routes of
exposure when dealing with
chemicals. Despite a multitude of
potential routes of exposure to
chemicals, most chemicals have a
limited number of major routes.
Factors That Determine Concentrations
of Chemicals Organisms Experience
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Solubility – how well a chemical can dissolve in a
liquid.
Biomagnification –is the increase in chemical
concentration in animal tissues as the chemical moves
up the food chain.
Persistence of a chemical refers to how long the
chemical remains in the environment.
Factors That Determine Concentrations
of Chemicals Organisms Experience
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Figure 17.21 The
biomagnification of DDT.
The initial exposure is
primarily in a low trophic
group such as the plankton
in a lake. Consumption
causes the upward
movement of the chemical
where it is accumulated in
the bodies at each trophic
level and upward movement
by consumption allows the
concentration to magnify.
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Persistence
Table 17.2 shows how scientists often measure persistence by
observing the time needed for a chemical to degrade to half its
original concentration, or the half life of the chemical.
Risk analysis helps us assess, accept,
and manage risk
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Table 17.22 shows the process of risk analysis. Risk
analysis involves risk assessment, risk acceptance, and risk
management.
Risk analysis helps us assess, accept,
and manage risk
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Table 17.23 show
probabilities of death in the
United States. Some factors
that people perceive as
having high risks of death,
such as dying in an airplane
crash, actually are quite
low. In contrast, some
factors that people rate as
low risk such as dying from
heart disease, actually pose
the greatest risk.
Qualitative Risk Assessment
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Making a judgment of the relative risks of
various decisions
Probability- the statistical likelihood of an
event occurring and the probability of that
event causing harm
Quantitative Risk Assessment
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The most common approach to conducting a
quantitative risk assessment can be expressed
with a simple equation:
Risk= probability of being exposed to a hazard
X probability of being harmed if exposed
Risk Management
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Risk management integrates the scientific data
on risk assessment and the analysis of
acceptable levels of risk with a number of
additional factors including economic, social,
ethical, and political issues.
Worldwide Standards of Risk
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The innocent-until-proven-guilty principle is
based on the philosophy that a potential
hazard should not be considered a hazard
until the scientific data can definitively
demonstrate that a potential hazard actually
causes harm.
The precautionary principle is based on the
philosophy that when a hazard is plausible but
not yet certain, we should take actions to
reduce or remove the hazard.
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Worldwide Standards of Risk
Figure 17.25 shows two different philosophies for managing
risk. The innocent-until-proven-guilty principle requires that
researches prove harm before the chemical is restricted or
banned. The precautionary principle requires that when there
is scientific evidence that demonstrates a plausible risk, the
chemical must then be further tested.
International Agreements on
Hazardous Chemicals
Stockholm Convention
• In 2001, a group of 127 nations gathered in Stockholm,
Sweden, to reach an agreement on restricting the
global use of some chemicals
• 12 chemicals were to be banned, phased out, or
reduced
• These include DDT, PCBs, and certain chemicals that
are by-products of manufacturing processes.