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Potency Estimates

EPA uses estimates of a chemical's potency, derived from the slope of the dose-response curve, as a single value in the risk-assessment process.

EPA should continue to use potency estimates—i.e., unit cancer risk—to estimate an upper bound on the probability of developing cancer due to lifetime exposure to one unit of a carcinogen. However, uncertainty about the potency estimate should be described as recommended in Chapter 9.

Although EPA routinely cites available human evidence, it does not always rigorously compare the quantitative risk-assessment model based on rodent data with available information on molecular mechanisms of carcinogenesis or with available human evidence from epidemiological studies.

Because the validity of the overall risk-assessment model depends on how well it predicts health effects in the human population, EPA should acquire additional expertise in areas germane to molecular and mechanistic toxicology. In addition, EPA should also acquire additional epidemiological data to assess the validity of its estimates of risk. These data might be acquired in part by formalizing a relationship with the National Institute for Occupational Safety and Health to facilitate access to data from occupational exposures.

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