Chapter 17 Human Health and Environmental Risks

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Chapter 17 Human Health and Environmental Risks
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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.

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• 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

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Three categories of human health risks

• 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

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Biological risk causes the greatest number of
deaths (both greens, red purple sections)
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Biological Risks

• 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

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Biological Risks

• All diseases fall into two categories
• Chronic disease- slowly impairs the functioning
  of a persons body.
• Acute diseases- rapidly impair the functioning of
  a persons body.

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Substantial difference in the top 10 risk factors
for death/chronic disease between low-income and
high-income countries
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Methods of Transmission

• 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

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Epidemic/Pandemic

• Epidemic rapid increase in a disease.
• Pandemic when an epidemic occurs over a large
  geographic region.

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Historical Diseases

• 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.

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Emergent Diseases

• 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 cows 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.

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• 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
• 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
  animals body. Scientists are finding many fish,
  reptiles, and amphibians that are male but have
  low sperm counts or are producing eggs and sperm.

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Lecture day 2

• Human Health and Environmental Risk

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Dose-Response Studies

• LD50- lethal dose that kills 50 of the
  individuals
• 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
• Mice and rats used to represent mammals, pigeons
  and quail used for birds, trout for fish, water
  fleas for invertebrates.

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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.

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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.

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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
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• Routes of Exposure

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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.

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Biomagnification

• Biomagnification- the increase in a chemical
  concentration in animal tissues as the chemical
  moves up the food chain.

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Persistence

• Persistence- how long a chemical remains in the
  environment

Scientists often measure persistence in its
half-life.
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Lecture day 3

• Human Health and Environmental Risk

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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

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Risk Analysis
Identify the hazard and magnitude. 2 types
qualitative and quantitative
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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).

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Quantitative Risk Assessment

• The approach to conducting a quantitative risk
  assessment is
• Risk probability of being exposed to a hazard X
  probability of being harmed if exposed

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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.

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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.

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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.

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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.
• All are endocrine disruptors.
• In 2009, 9 additional chemicals were added to the
  original list of 12 and several more have been
  suggested.

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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.