RISK, TOXICOLOGY, and HUMAN HEALTH

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RISK, TOXICOLOGY, and HUMAN HEALTH

• Risk A measure of the likelihood that you will
  suffer harm from a hazard

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Risk Expressed as a probablility

• Injury
• Disease
• Death
• Economic loss
• Environmental danger
• Scientific process of determining the probability
  something bad will happen to you

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Types of Hazards

• Physical (fire, earthquake)
• Chemical
• Biological (pathogens, animals)
• Cultural (diet, poverty,smoking)

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Toxicology assessing chemical hazards the
measure of how harmful a substance is

• Dose (amount ingested, inhaled, absorbed)
• Frequency of exposure
• Who is exposed (child vs adult)

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5 factors that can affect the harm caused by a
substance

• Solubility (water vs. lipid)
• Persistence (how long it remains)
• Bioaccumulation (stored in organs or tissues)
• Biomagnification (toxicity increases up the
  trophic levels)
• Chemical interactions
• a. Antagonistic cancels out
• b. Synergistic multiplies harmful effects

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Basic Tenet of Toxicity

• Any synthetic or natural chemical can be harmful
  if ingested in a large enough quantity
• The Question Then
• How much is too much?

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Mechanisms for reducing harmful effects

• Breakdown usually in the liver
• DNA enzymes for repair
• Certain cells can be replicated faster to replace
  damaged cells (skin, GI tract, blood vessels)

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Estimating Toxicity (without testing humans!)

• Median Lethal Dose (LD50) the amount received
  in 1 dose that kills 50 of animals tested
  usually mice or rats
• The EPA most wanted list of toxic substances
• Arsenic 4. Vinyl cloride
• Lead 5. polychlorinate
• Mercury biphenyls (PCBs)
• These represent the top 5 of the 276 substances
  regulated by the Superfund Act (Love Canal)

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Types of Chemical Hazards

• Mutagens increase frequency of mutations
• Teratogens harm developing fetus
• Carcinogens cause/promote cancer
• Long term chemical exposure affects
• Nervous system
• Immune system
• Endocrine system

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EPA is NOT the same as the FDA!

• Current federal and state regulations only affect
  0.5 of commercially used chemicals in the U.S.
• Why?
• innocent until shown to be guilty
• Not enough funds, people, facilities, or test
  animals
• Difficult and expensive to analyze combined
  effects and interactions

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BIOLOGICAL HAZARDS

• Transmissible vs nontransmissible
• Transmissible bacteria, virus, parasites ?
  pathogens ? 25 of deaths
• Nontransmissible heart disease, diabetes,
  asthma ? 30 of deaths (data from WHO)
• In industrialized countries infectious diseases
  decrease and chronic adult disease increases

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WHO 7 Deadliest

• Pneumonia/Flu 3.2 mil
• HIV/AIDS 3.0 mil
• Gastrointestinal 1.9 mil
• TB 1.7 mil
• Malaria 1 mil
• Hep B 1 mil
• Measles 800,000

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Calculating Risk Risk Analysis

• Ways to evaluate and compare risk
• Determine how much is acceptable
• A scientific process of analyzing PAST results
  (epidemiology)
• High-risk Health Problems
• Indoor/outdoor air pollution
• Polluted water
• Toxic chemicals in consumer products/food

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• High risk ecological problems
• Global climate change
• Ozone depletion
• Habitat destruction
• Loss of biodiversity
• Medium-risk ecological problems
• Acid deposition
• Pesticides
• Toxic material in surface water
• Low risk ecological problems
• Oil spills
• Radioactive isotopes
• Thermal pollution

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Why is risk analysis so risky?

• Use of old data
• Who is doing the data analysis (do they benefit
  from the results?)
• Short term vs long term risks
• Are cummulative effects taken into consideration
  (synergistic effects)
• How many people will be affected? How many is
  too many?
• Risk analysis for different groups (i.e. workers
  vs. the general public consider nuclear power
  plants)
• Who decides what is acceptable? WHO? EPA? FDA?
  Parents? Teachers?

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Your Individual Perception of Risk

• Misleading information
• Misrepresented data
• Level of participation
• Cultural exposure
• Distribution
• In general, your sense of risk is defined by
• Degree of control (wearing your seatbelt)
• Fear of the unknown (gen. altered foods)
• Voluntary vs. involuntary (driving vs. power
  plants)
• Catastrophic vs. chronic (plane crash vs smoking)