Review of the Environmental Protection Agency's Draft IRIS Assessment of Tetrachloroethylene (2010) / Chapter Skim
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12 Moving Beyond the Current State of Practice
12 Moving Beyond the Current State of Practice
Pages 114-120
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From page 114... ...
They include improvements in the presentation and organization of information, addition of transparency in documenting procedures used for identifying and selecting studies, and the use of evolving approaches to uncertainty analysis. Guidance in many of these areas is provided in a recent National Research Council (NRC 2009)
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From page 115... ...
Attention to specifying evaluation criteria and the options considered is expected to contribute considerably to transparency in the separation of science judgment from science-policy choices. To increase transparency, accountability, and defensibility and to improve the content and process of assessments, the committee offers the following recommendations regarding future assessments of tetrachloroethylene: The nature of, timeframe for, and extent of consideration of relevant data should be clearly framed and stated (for example, standard searching of identified electronic sources with criteria specified, cutoff date past which no additional data were considered, and identification of current studies by reviewers)
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From page 116... ...
. On numerous occasions, the National Research Council has explicitly called for the use of probabilistic risk assessment (NRC 2006b, 2007)
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From page 117... ...
, an enumeration of the relevance of probabilistic risk analysis to decision-making, common challenges faced by decision-makers, an overview of probabilistic risk-analysis methodology, and recommendations on how probabilistic risk analysis can support regulatory decision-making. EPA's National Exposure Research Laboratory has recently explored methodologic issues in dealing with uncertainty quantitatively when air-quality, exposure, and dose models are coupled (Ozkaynak et al.
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From page 118... ...
. The need for characterization of uncertainty in risk characterization is supported by numerous National Research Council studies (for example, NRC 1994)
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From page 119... ...
In this approach, a prior distribution is postulated to the options on a key assumption, such as the one for MOA, or a key choice, such as candidate data sets. Each final risk estimate is a result of a combined set of assumptions and choices propagating through the risk-assessment process tree and is assigned a probability that results from the prior probabilities assigned to each associated assumption and choice.
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From page 120... ...
Some quantitative techniques that were explored were bootstrap simulation and probabilistic inversion with isotonic regression and Bayesian-model averaging to deal with uncertainty in model structure. However, although there is not yet a default method for quantifying uncertainty in dose-response relationships, EPA can and should review and adopt or adapt various methods that are being explored in the scientific community, taking particular note of the possibilities for combining expert judgment and data with Bayesian approaches.
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