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Review of the U.S. Army's Health Risk Assessments for Oral Exposure to Six Chemical-Warfare Agents (1999) / Chapter Skim
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2: Derivation of Reference Doses
Pages 17-23

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From page 17...
... Those methods were based on the procedures outlined by the U.S. Environmental Protection Agency for Superfund risk assessment guidelines (EPA 1989)
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From page 18...
... , UF1 represents the expected ratio of the LOAEL to the NOAEL when a LOAEL is used instead of a NOAEL, IS represents the uncertainty of predicting chronic exposure effects on the basis of subchronic exposure studies, UFD represents the uncertainty assigned to an inadequate data base, and ME is a modifying factor to account for any additional uncertainty not addressed by the standard uncertainty factors. Typically, uncertainty factors are assigned values ranging from ~ to 10.
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From page 19...
... A modifying factor between ~ and 10 is used when the five uncertainty factors do not explicitly account for all scientific uncertainties that exist. The default value for the modifying factor is I
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From page 20...
... Environmental Protection Agency (EPA 1996) , a BD approach based on uncertainty factors is one of the methods suggested when a nonlinear dose response is expected (e.g., for nongenotoxic carcinogens or tumor promoters)
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From page 21...
... Thus, it appears that the conventional products of 10 for default values of uncertainty factors provide reasonable assurance of safety.
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From page 22...
... EPA (U.S. Environmental Protection Agency)
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From page 23...
... 1995. Selecting a more realistic uncertainty factor: Reducing compounding effects of multiple uncertainties.
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Key Terms

  • default values
  • chronic exposure
  • modifying factor
  • reference doses
  • risk assessments

  • health risk
  • reference dose
  • susceptible subpopulations
  • human population
  • oral reference

  • deleterious health
  • excess risk
  • exposure studies
  • five uncertainty
  • lower confidence

  • superfund risk
  • traditional rfd
  • subchronic exposure
  • total uncertainty
  • confidence limit

  • overall product
  • dose chosen
  • uncertainty spanning
  • risk associated
  • reference concentrations

  • effects compared
  • default value
  • computer simulations
  • carcinogen risk
  • upper bounds


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