Transcript Chapter 17 Human Health and Environmental Risks

Chapter 17
Human Health and Environmental Risks
Norco, Louisiana
• Old Diamond district: Four city blocks
between A Shell Oil chemical plant and a
refinery. Minority neighborhood.
• 1973-pipeline explosion: 2 dead
• 1988-refinery accident 7 workers killed, 70
mill. Kg of toxic chemicals released into air,
nearly 1/3 of all children suffered asthma,
many cases of birth defects and cancers after.
• 1989- middle school teacher Margie Richard takes
action.
– Set up a “bucket brigade” to collect air samples.
– Fight against shell withstood large resistance from the
company. 13 year fight.
• 2002- Shell pays $5 million to community for development,
buys resident houses at fair market price, committed to
reducing air emissions by 30%
• 2007- pays an addition $6.5 million in penalties to the state
for violation of air pollution regulations
Three categories of human health
risks
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Physical
 Natural disasters, excessive exposure to UV
radiation, exposure to radioactive substances
like radon.
Biological
 Risks associated with disease
Chemical
 Exposure to chemicals ranging from naturally
occurring arsenic to synthetic chemicals and
pesticides
Biological risk causes the greatest number of
deaths: (both greens, red & purple sections)
Biological Risks
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Infectious diseases- those caused by infectious
agents, known as pathogens.
The pathogens that cause most infectious diseases
are viruses, bacteria, fungi, protists, and a group of
parasitic worms called helminths.
Examples: pneumonia and venereal diseases
Biological Risks
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All diseases fall into two categories:
 Chronic disease- slowly impairs the functioning
of a person’s body.
 Acute diseases- rapidly impair the functioning of
a person’s body.
Substantial difference in the top 10 risk factors
for death/chronic disease between low-income
and high-income countries…
Methods of Transmission
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Environmental Scientists
are interested in diseases
caused by environmental
factors (not genetic
diseases)
Many pathways to
infecting humans,
including transmission
of pathogens from other
humans, other animals,
the food we eat, the
water we drink…
Epidemic/Pandemic
• Epidemic: rapid increase in a disease.
• Pandemic: when an epidemic occurs
over a large geographic region.
Historical Diseases
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Plague
– Carried by fleas found on rodents
– Modern antibiotics highly effective.
Malaria
– Transmitted by several species of plasmodium.
– One cycle of life in mosquito, one cycle in humans.
– 1951- malaria eradicated from US. Traditional approach: DDT.
Tuberculosis
– Caused by bacterium M. tuberculosis . Primarily affects lungs
– Can persist in air for several hours, may be infected without signs or symptoms
– Drug resistant strains are a problem.
Emergent Diseases
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Infectious diseases that have not been seen within the last 20
years.
Many of these new diseases have unexpectedly jumped from one
species to another through mutation.
HIV/AIDS: origin remained a mystery until 2006 when the
original host was found to be chimpanzees. Antiviral drugs have
held it in check where available.
Ebola: Caused by ebola virus. Originated in the Congo. Kills
most that are infected with it.
Mad Cow Disease: Damages cow’s nervous system. Small
beneficial proteins called prions mutate into deadly proteins that
act as pathogens. Passed from cow to cow when fed with ground
up cows infected with disease as an extra source of protein.
Passed to humans who eat infected cows.
Bird Flu: Avian influenza. Caused by
H1N1. similar to an Asian virus known
as H5N1 that had jumped from bird to
human. Because there is no
evolutionary history for humans, they
tend not to have defenses against it.
 West Nile Virus: Transmitted among
birds via mosquitoes. Increasing
reports that horses and humans could
be infected if bitten by the mosquitoes.
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Chemical Risks
 Five categories of harmful chemicals:
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Neurotoxins- chemicals that disrupt the nervous system. Insects and other
invertebrates are extremely sensitive to neurotoxins. Lead, Mercury.
Carcinogens- chemicals that cause cancer. Interrupt the normal metabolic
function of a cell, damaging the genetic material. Carcinogens that damage
cells are called mutagens
Teratogens- chemicals that interfere with the normal development of
embryos or fetuses. Modern teratogen: Alcohol.
Allergens- chemicals that cause allergic reactions. Chemicals naturally
found in Milk, Peanuts, and drugs such as penicillin and codeine.
Endocrine disruptors- chemicals that interfere with the normal functioning
of hormones in an animal’s body. Scientists are finding many fish, reptiles,
and amphibians that are male but have low sperm counts or are producing
eggs and sperm.
Human Health and Environmental Risk
LECTURE DAY 2
Dose-Response Studies
LD50- lethal dose that kills 50% of the individuals
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Short duration (1-4 days) called acute studies.
The dose at which an effect starts to be seen is called the
threshold.
ED50- effective dose that causes 50% of the animals to
display the harmful but nonlethal effect
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Mice and rats used to represent mammals, pigeons and
quail used for birds, trout for fish, water fleas for
invertebrates.
Regulation of testing
• In the US the effects of chemicals on humans and
wildlife are regulated by the EPA.
– Toxic Substances Control Act 1976 (excludes food, cosmetics,
and pesticides).
– Pesticides are regulated under the Federal Insecticide,
Fungicide, and Rodenticide Act of 1996
– Since no chemical can be tested on every animal, scientists
have devised the system of using representatives of those
species.
– Reptiles and amphibians have not been species of interest in
the past and so aquatic reptiles and amphibians have been
represented by fish and terrestrial by bird tests.
Determining the concentrations
• To determine the concentration which will
cause no harm, scientists use the LD50 value
divided by 10.
• For humans, they use the LD50 value
(obtained from mice and rats) divided by
1000.
Chronic studies
• For studies lasting longer than a few days.
• Retrospective studies: monitor people who
have been exposed to a chemical at some
time in their past.
• Prospective studies: monitors people who
might become exposed to harmful chemicals
in the future. (select 1000 people and follow
them for 40 years monitoring their tobacco,
alcohol, etc. and future health affects.)
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Synergistic interactions- when two risks come
together and cause more harm that one
would. For example, the health impact of a
carcinogen such as asbestos can be much
higher if an individual also smokes tobacco.
Smoking
and
Sunbathing
Routes of Exposure
Bioaccumulation
Bioaccumulation- an increased concentration of a chemical
within an organism over time
Solubility- how well a chemical can dissolve in a liquid
Some are water soluble: pervasive in ground water and
surface water.
Some are oil-soluble: pervasive in soils (especially benthic
soils). Readily stored in the body fat of animals.
Biomagnification
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Biomagnificationthe increase in a
chemical
concentration in
animal tissues as the
chemical moves up
the food chain.
Persistence
Persistence- how long a chemical remains in the environment
Scientists often measure persistence in its half-life.
Human Health and Environmental Risk
LECTURE DAY 3
Environmental Hazard
• Anything in our environment that can
potentially cause harm.
– Pollutants, human activities, natural catastrophes.
• When assessing risk of different
environmental hazards, regulatory agencies,
environmental scientists, and policy makers
usually follow a three step process:
Risk Analysis
Identify the hazard and magnitude.
2 types: qualitative and quantitative
Qualitative Risk Assessment
• We tend to categorize our decisions based on
having low, medium, or high risk.
• Based on judgments rather than actual data.
– These judgments often do not match the actual
risk.
– Lack of familiarity, extent to which the act is
Voluntary, public impression (big events imprint in
our minds), overselling of safety, morality, control,
fairness (knowing who benefits).
Quantitative Risk Assessment
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The approach to conducting a quantitative risk
assessment is:
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Risk= probability of being exposed to a hazard X
probability of being harmed if exposed
Risk Acceptance
• The level of risk that can be tolerated.
• Personal preferences always play a part in
complicating the decision. Environmental
scientists, policy makers, economists, etc.
help to weigh the options objectively.
Risk Management
• Seeks to balance possible harm against other
considerations.
• Integrates the scientific data and the
acceptable levels of risk with a number of
additional factors including economic, social,
ethical, and political issues.
• Regulatory activity usually carried out by
local, national, or international government
agencies.
Standards of Risk
• Innocent-until-proven-guilty principle: gets chemicals to
public faster but may introduce a potential hazard to fast
and therefore cause harm to the public or environment.
– US policy.
• Precautionary principle: when a hazard is plausible but not
yet certain. Delays the chemical getting to the public in a
timely manor. Cost manufacturer more money. Many of
the chemicals are never researched or found because the
time and money investment is not worth the time.
– Policy used by the European Union.
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
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12 chemicals were to be banned, phased
out, or
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reduced
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These include DDT, PCBs, and certain
chemicals
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that are by-products of manufacturing
processes.
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All are endocrine disruptors.
In 2009, 9 additional chemicals were added
to the original list of 12 and several more
have been suggested.
REACH
• 2007, the 27 nations of the European Union
put into effect an agreement on how
chemicals should be regulated within the
European Union. Registration, evaluation,
authorization, and restriction of chemicals.
• Embraces the precautionary principle.