Chapter 14 Environmental health and Toxicology

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Chapter 14 - Environmental health and Toxicology

• Environmental health
• Assesses environmental factors that influence
  human health and quality of life.
• Seeks to prevent adverse effects on human health
  and ecological systems.
• Contains environmental toxicology within its
  scope.

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Environmental health hazards
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Infectious disease
6 diseases account for 80 of infectious disease
deaths
2nd-leading cause of death worldwide
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West Nile Virus
West Nile Virus has spread rapidly since 1999.
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Many health hazards exist indoors

• Substances in plastics and consumer products
• Lead in paint and pipes
• Radon
• Asbestos
• PBDE fire retardants

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Toxicology

• The study of poisonous substances and their
  effects on humans and other organisms
• Toxicologists assess and compare toxic agents, or
  toxicants, for their toxicity, the degree of harm
  a substance can inflict.
• Analagous to a pathogenicity or virulence of the
  biological hazards that spread infectious
  disease.
• Environmental toxicology focuses on effects of
  chemical poisons released into the environment.

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Synthetic chemicals

• Of the 100,000 synthetic chemicals on the market
  today, very few have been thoroughly tested for
  harmful effects.

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Synthetic chemicals are numerous
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Rise of synthetic chemicals

• Widespread synthetic chemical production after
  WWII
• People are largely unaware of the health risks of
  many toxicants.

The potent insecticide DDT was sprayed widely in
public areas, even on people.
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Silent Spring and Rachel Carson

• Carsons 1962 book alerted the public that DDT
  and other pesticides could be toxic to animals
  and people.
• Further research led the EPA to ban DDT in 1973.
• These developments were central to the modern
  environmental movement.

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Types of toxicants Teratogens

• The drug thalidomide, used to relieve nausea
  during pregnancy, turned out to be a potent
  teratogen, and caused thousands of birth defects
  before being banned in the 1960s.
• Thalidomide baby Butch Lumpkin learned to
  overcome his deformed arms and fingers to become
  a professional tennis instructor.

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Endocrine disruption

• Some chemicals, once inside the bloodstream, can
  mimic hormones.
• If molecules of the chemical bind to the sites
  intended for hormone binding, they cause an
  inappropriate response.
• Thus these chemicals disrupt the endocrine
  (hormone) system.

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A Toxic Hand-Me-Down Michael Balter ScienceNOW
Daily News 27 March 2007Environmental
contamination can cause cancer and birth defects.
Of particular concern are a group of toxic
chemicals called endocrine-disrupters, which
interfere with reproductive hormones and may
cause sterility. A new study, published online
this week in the Proceedings of the National
Academy of Sciences, suggests that these
chemicals can change reproductive behavior as
well, and that these behavioral changes can be
passed on from parents to offspring. If correct,
these changes could alter the course of evolution
by giving natural selection new targets to act on.
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Frogs, people, and atrazine
Atrazine is a popular corn herbicide
Frogs show reproductive abnormalities in
response to small doses of the herbicide
atrazine, researcher Tyrone Hayes
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Declining sperm counts?
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Testicular cancer

• Others hypothesize that endocrine disruptors are
  behind the rise in testicular cancer in many
  nations.

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Toxicants take many routes through the environment
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Transport to the Arctic Global distillation
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Poisons move up the food chain

• At each trophic level, chemical concentration
  increases biomagnification.
• DDT concentrations increase from plankton to fish
  to fish-eating birds.

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Human epidemiology

• Human studies rely on
• Case history observation and analysis of
  individual patients
• Epidemiological studies long-term, large-scale
  comparisons of different groups of people
• Animal testing

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Dose-response curve
LD50 dose lethal to 50 of test animals
Threshold dose at which response begins
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Risk

• Risk the mathematical probability that some
  harmful outcome will result from a given action,
  event, or substance
• Probability a quantitative description of the
  likelihood of a certain outcome
• Harmful outcome could be defined as injury,
  death, environmental damage, economic loss, etc.

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Risk assessment

• Involves
• Dose-response analysis or other tests of toxicity
• Assessing likely exposure to the hazard
  (concentration, time, frequency)

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Risk management

• Consider risk assessments in light of social,
  economic, and political needs and values.
• Weigh costs and benefits, given both scientific
  and nonscientific concerns.
• Decide whether or not to reduce or eliminate risk.

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Risk assessment and risk management inform policy

• Following risk management, policy decisions are
  made.

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Implications for product testing

• Industry has pressured government to take an
  innocent-until-proven-guilty approach.
• Environmental advocates have pressured government
  to follow the precautionary principle.

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Federal agencies and risk management

• In the U.S., most risk management is conducted by
  federal and state agencies.
• Particularly
• Environmental Protection Agency
• and
• Food and Drug Administration

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Policy on toxicants

• Key agencies and products they regulate
• Food and Drug Administration (FDA)
• food, additives, cosmetics, drugs, medical
  devices
• Environmental Protection Agency (EPA)
• pesticides, industrial chemicals, and any
  synthetic chemicals not covered by other
  agencies
• Occupational Health and Safety Administration
  (OSHA)
• workplace hazards

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QUESTION Review

• Which causes birth defects?
• a. Allergen
• b. Mutagen
• c. Carcinogen
• d. Teratogen
• e. Endocrine disruptor

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QUESTION Review

• Which statement is NOT correct regarding the
  insecticide DDT?
• a. It was criticized in the book Silent Spring.
• b. It helps fight malaria.
• c. It is persistent and bioaccumulates.
• d. It has no toxic breakdown products.
• e. Its use was banned by the EPA.

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QUESTION Review

• Epidemiological studies ?
• a. Can prove a certain toxicant causes a
  certain effect.
• b. Search for statistical association between
  hazard and effect.
• c. Are rapidly completed.
• d. Take place with lab animals.

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QUESTION Interpreting Graphs and Data

• The curve demonstrates ?
• a. The point at which 20 of the animals are
  killed
• b. The percentage of animals affected decreases
  with the dose
• c. The percentage of animals affected increases
  with the dose