Where there is food there are many problems' Where there is no food there is only one problem'

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Where there is food there are many
problems.Where there is no food there is only
one problem.
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Conflicting Information about the Risk Caused by
Agricultural Chemicals comes from Differences of
Opinion on what is an Acceptable Risk
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Current Cancer Risk

• 200000 people per million will die of cancer
  (210)

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EXAMPLES OF 1 per million CANCER RISK

• Living 20 days at sea level because of natural
  background radiation
• Living 2.5 months in a masonry house rather than
  a wood frame house (added radiation from masonry)
• Taking a round-trip coast-to-coast flight (added
  radiation at high altitude.)

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EXAMPLES OF 1 per million CANCER RISK

• Drinking 40 diet pops containing saccharin
• Smoking 2 cigarettes
• Eating 6 pounds of peanut butter (from aflatoxin
  mold found in peanuts)

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EXAMPLES OF 1 per million Death Risk in USA

• Every Day from Car Accidents
• Every 6 days from an ordinary fall
• Every 13 days from fire

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PERCEIVED RISK

• LOW
• Voluntary Risk
• Natural Source
• Familiar Source
• Immediate Effect
• Continuous Exposure

• HIGH
• Involuntary Risk
• Synthetic Source
• Unfamiliar Source
• Delayed Effect
• Occasional Exposure

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PERCEIVED RISK

• LOW
• Controllable Risk
• Clear Benefits
• Substance is necessary

• HIGH
• Uncontrollable Risk
• Unclear Benefits
• Substance is a luxury

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ACCEPTABLE RISK DEFINED BY

• GUIDELINES (MCL, HA)
• ZERO TOLERANCE
• PROBABILITIES

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WHAT IS THE RISK OF ONE TICKET WINNING THE
LOTTARY?

• 45 NUMBERS
• 6 NUMBERS PER TICKET
• HOW MANY COMBINATIONS OF 6 ARE POSSIBLE?
• 8,147,381

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RISK ASSESSMENT

• Hazard Identification
• Dose-Response Assessment
• Human Exposure Assessment
• Risk Characterization

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HAZARD IDENTIFICATION

• Is the particular substance toxic?
• Does it produce harmful effects?
• What is the nature of the harmful effects?
• cancer, cell mutations, damage to organs damage
  to blood forming, nervous, or immune systems,
  birth defects, damage to reproductive systems

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SOURCES OF TOXIC DATA

• Epidemiology Studies (statistical cause-effect
  studies)
• Animal exposure studies
• Short-term bioassays using cell cultures
• Molecular structure analysis relate a chemical
  to a chemical with similar molecular structure
  with known toxicity.

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EPIDEMIOLOGY STUDIES

• Case Control Studies Look at the commonalities
  in past exposure that might account for everyone
  in a group having a common health problem.
• Everyone lived in the same community at some
  time.
• Everyone is a smoker

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EPIDEMIOLOGY STUDIES

• Cohort Studies Look at a group of people with
  similar exposure histories and compare their
  health status.
• Everyone exposed to agent orange
• Everyone who is a smoker

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Characteristics of Epidemiology Studies

• Only direct measure of effects on human health
• Does provide information from actual exposure
• Accurate data on exposure levels is not readily
  available
• People frequently aren't aware of all their
  exposure experiences

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Characteristics of Epidemiology Studies

• Difficult to find a control group
• Difficult to sort out confounding exposure
• The absence of an effect does not guarantee that
  there is no effect.
• Differences in length of time of the exposure, or
  the intensity of the exposure may effect the
  results.

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ANIMAL STUDIES TO DETERMINE TOXICITY

• This is the primary method used
• All chemicals that are carcinogenic to humans
  have been found to cause cancer in at least some
  animals
• Toxicity levels for most chemicals are similar in
  humans and animals.
• At the cell level, humans and animals are very
  similar

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TYPES OF ANIMAL STUDIES

• Acute
• Oral (LD50)
• Dermal
• Inhalation(LC50)
• Chronic
• Teratogenic (birth defects) Mutagenic
• Primary skin irritation
• Skin Sensitization (allergies)
• Primary eye irritation

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TYPES OF ANIMAL STUDIES

• Fertility and Reproductive
• Prenatal and Postnatal
• Multi-generational (3 generations)

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LIMITATIONS OF ANIMAL STUDIES

• Differences between animals and humans
• weight, metabolic differences, Life span
  differences
• Differences between species
• Only about 30 of the chemicals that are
  carcinogenic to mice are carcinogenic to rats,
  and visa versa.
• There is a lot of concern among animal rights
  activists about animal studies.

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SHORT TERM TESTS

• Rapid and inexpensive
• Designed to detect gene mutations
• Results not well correlated with animal studies
• Used for identification of carcinogens
• Not used to set standards

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DOSE RESPONSE TESTING

• The response at very low dosage levels is not
  known.
• For carcinogens, there is no threshold level
  assumed.
• There are always cases of cancer in the check
  group. Therefore it takes large numbers to
  detect an increased rate of cancer due to any
  particular cause.

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DOSE RESPONSE TESTING

• Test are run at very high dosage levels and
  mathematical models are used to extrapolate down
  to normal exposure levels. The choice of the
  mathematical model can make a big difference.
  Different models can differ by a factor of 106 in
  some cases. The linear multi-state model Take
  the lowest point and draw a straight line from
  there to 0. Add on a 95 Confidence interval and
  use the upper limit of this.

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TYPICAL DOSE-RESPONSE DATA SUMMARY
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DIFFERENCES IN TOXICITY OF TCDD(dioxin) AMONG
DIFFERENT SPECIES
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EPA IRIS Substance List

• Integrated Risk Information System
• www.epa.gov/ iris/ subst/ index.html