Toxicology, Human Health and Risk Assessment

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Toxicology, Human Health and Risk Assessment
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Toxicology

• Study of the adverse effects of chemicals on
  health.

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Types of Hazards/Pollutants

• Particulates
• Allergens
• Asbestos/RFAs
• EMFs
• Noise Pollution
• Teratogens

• Infectious Agents
• Toxic Heavy Metals/Neurotoxins
• Organic Compounds/Neurotoxins
• Radiation

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Infectious Agents

• TB (air)
• Dysentery (water)
• AIDS (body fluids)
• Flu (air)
• Cholera (water)
• Yellow Fever (mosquitoes)
• Giardia (water)
• Malaria (mosquitoes)
• Guinea Worm (water)
• Lyme Disease (ticks)

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Infectious Disease Deaths

• Why different from book?

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Toxic Heavy Metals

• Mercury
• Burning coal and wastes
• Minimata (vinyl chloride plant)
• mad hatter
• tuna
• Cadmium
• Burning coal
• Chromium
• Electricity generation
• Effects
• Neurological problems
• Acute poisoning
• leukemia

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Organic Compounds

• POPs (persistent organic pollutants)
• DDT (pesticide)
• Dioxin (herbicide production, burning of waste)
• PCBs (electricity transformers GE Hudson)
• Effects
• Carcinogen
• Immune/reproductive/endocrine failure

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Ionizing Radiation

• Sources
• X-rays
• Cosmic Rays
• Radon Gas
• Effects
• major cause of cancers (carcinogenic)

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Particulates

• Small particles of dust, ash, dirt, etc.
• Caused by
• Desertification
• Erosion
• Volcanoes
• Fires
• More about this later

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Allergens

• Sources
• Pollen
• Diet
• Formaldehyde
• Effects
• Allergic reaction
• Sensitizing to other chemicals
• Sick building syndrome

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Respiratory Fibrotic Agents

• Examples
• Asbestos
• Used for fire prevention in building materials
• Insulation
• Fiberglass
• Coal Dust
• Effects
• Build-up of scar tissue on lungs
• Decrease in respiratory efficiency

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EMFs

• Sources
• Motors, hair dryers, appliances, power lines,
  cell phones, etc.
• Effects
• evidence suggesting increase in childhood
  leukemia and brain cancer

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Noise Pollution

• Causes
• Roads, construction, factory work, music, etc.
• Effects
• Permanent hearing loss
• Stress which affects immune system

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Teratogens

• Chemicals that cause birth defects
• Example
• Thalidomide
• Used as a tranquilizer in Europe
• Caused thousands of children with shortened limbs

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Cultural/ Voluntary Hazards

• Diet
• Smoking
• smoking is the nations leading cause of
  preventable death
• equivalent to 3 jumbo jets crashing every day
  (1150/day)
• only 1 in ten can quit
• Unsafe Sex
• Drinking

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RISK ANALYSIS
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What is risk analysis?

• It can be defined as the process of determining
  the risks associated with a particular hazard and
  taking some action in which the hazard is present
• Who performs risk analysis?
• The EPA
• began in 1970s to estimate cancer risks as a
  result of exposure
• What are the 4 steps?
• 1. Risk assessment 3. Exposure assessment
• 2. Dose-response assessment 4. Risk
  characterization

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1. Risk assessment

• determining types of hazards involved
• probability that each will occur
• how many people will be exposed
• how many will suffer serious harm
• two methods
• epidemiology - study that tracks how a sickness
  spreads through a community - can establish
  links
• animal testing - gives more immediate results

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2. Dose-response assessment

• establishment of relationship between dose and
  response
• dose- amount of substance that someone has
  ingested, inhaled or absorbed
• acute exposure - single dose
• chronic exposure - long-term exposure
• response - type and amount of damage
• acute effect - immediate or rapid reaction to
  exposure
• chronic effect - permanent or long-lasting effect

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Dose-response Curves

• A) some individuals respond even at 0 dose - some
  other factor causing response
• B) linear relationship - for some carcinogens
• C) linear plus threshold - minimal dosage
  necessary for response

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Measuring Toxicity LD50

• Chemicals (poisons) are rated according to their
  LD50 (lethal dose) value
• LD50 is the amount of a chemical that is required
  in one dose to kill 50 of test population in 14
  days
• the smaller the LD50, the more toxic the material

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Solubility

• One of the most important characteristics
  determining how a toxin will move through a body
  or environment
• water-soluble compounds move rapidly in
  environments and throughout the body
• fat-soluble compounds have trouble getting into
  body, but once in readily penetrate cells
• are bioaccumulated leading to biomagnification

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Persistence and Chemical Interactions

• Persistence - how long a chemical remains in the
  environment - good and bad
• Chemical interactions
• antagonistic effects - interfere with the effects
  of or stimulate the breakdown of other chemicals
  antioxidants A B lt AB
• additive effects - effects are added together AB
  AB
• synergistic effects - when combination is worse
  than added effects AB gt AB

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3. Exposure Assessment

• Estimation of intensity, duration, and frequency
  of human exposure to hazard
• exposure hazard is proportional to population
  exposed and inversely proportional to distance
  from source

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4. Risk characterization

• Pull together all of the information in the first
  three steps to determine the magnitude of the
  risk and its accompanying uncertainties
• Can also include comparative risk analysis
• comparing the risks to order them in terms of the
  greatest risks to human health
• this information can then be passed on the the
  public

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Cost-benefit analysis

• Comparison of the costs of a program (ex.
  pollution clean-up) to the benefits of the
  program
• Cost usually increases non-linearly with amount
  of reduction
• Benefits do not increase linearly (fall off at
  high reduction level)

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Cost-benefit analysis
How much are we willing to pay for
clean-up? Most cost-effective strategy use of
funds is represented in green
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Risk-benefit analysis

• What are the benefits of the exposure relative
  the risks of exposure?
• X-rays

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Public preferences

• The public can have a huge influence on public
  policy
• This can be good, but the public isnt always
  informed, and may force politicians to allocate
  money in places that may not help the most people
• Also, people arent always informed about the
  most significant issues affecting them
• difference inn perceived risks vs. actual risks