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Issues in Risk Assessment (1993) / Chapter Skim
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CORRELATIONS
Pages 24-32

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From page 24...
... Please use the print version of this publication as the authoritative version for attribution. carcinogenic potency of an agent at low doses.
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From page 25...
... Please use the print version of this publication as the authoritative version for attribution. • Exposure to the test chemical did not notably reduce survival of the test animals in comparison with unexposed controls.
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From page 26...
... Please use the print version of this publication as the authoritative version for attribution. highest dose tested, which is assumed to correspond to an estimate of the MTD.)
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From page 27...
... The lower bound is determined by the number of animals tested at the MTD, the spontaneous tumor rate, and the level of statistical significance required to label a chemical as a carcinogen. For example, if there is a 10% spontaneous rate and 50 animals are tested at the MTD, at least 10 animals must respond at the MTD if an effect is to be declared statistically significant at the 5% probability level.
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From page 28...
... Although the latter chemicals cannot be positioned with precision in Figure 2-1, it is clear from the definition of the three regions that they are Region A chemicals; if they could be positioned in Region A, the observed correlations would probably be reduced. Thus, the committee concludes that the correlation between the MTD and the TD50 might apply not to all chemicals, but only to those with carcinogenic potency high enough to cause statistically significant increases in tumors in animals exposed at the MTD for a lifetime.
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From page 29...
... Please use the print version of this publication as the authoritative version for attribution. them.
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From page 30...
... Please use the print version of this publication as the authoritative version for attribution. FIGURE 2 Association between carcinogenic potency and maximum tolerated dose.
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From page 31...
... It is not clear what is an appropriate correction factor, so TD50s the basis of studies lasting less than the standard lifespan of the test species are more uncertain than those estimated on the basis of whole-lifespan studies. The effect of this adjustment factor on the correlation between the TD50 and the MTD warrants investigation, although ultimate resolution of this uncertainty would require retesting of these chemicals at lower doses for a full lifespan.
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From page 32...
... Please use the print version of this publication as the authoritative version for attribution. time bioassays; it is theoretically possible that these chemicals could be positioned substantially further out into Region C than is indicated by Figure 2-2.
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Key Terms

  • low dose
  • correction factor
  • dose carcinogenic
  • five chemicals
  • lower doses

  • lower bound
  • animals tested
  • carbon tetrachloride
  • observed correlations
  • benzidine dyes

  • potential region
  • animals exposed
  • cause statistically
  • test species
  • correlation coefficients

  • direct brown
  • upper confidence
  • suitable quantitative
  • significant increases
  • experimental designs

  • quantitative data
  • low carcinogenic
  • carcinogenic potencies
  • statistical upper
  • secant approximations

  • ingestion study
  • model applied
  • additional ingestion
  • selected subsets
  • increased cell


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