Review of the Environmental Protection Agency's Draft IRIS Assessment of Tetrachloroethylene http://www.nap.edu/catalog/12863.html
12 Moving Beyond the Current State of Practice
The committee found that the Environmental Protection Agency (EPA) draft Integrated Risk Information System (IRIS) assessment could be improved in several ways. Such changes are not necessary for completing the current assessment but should be considered when tetrachloroethylene is re-evaluated. 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) report Science and Decisions, which discusses advancing risk assessment practices. ORGANIZATION AND APPROACH There is a vast amount of literature on tetrachloroethylene, and drafting of the IRIS assessment was hampered by the need to manage such a large volume. EPA should consider ways of reorganizing the document to streamline the presentation of data and analyses. The current organization requires that some information be duplicated in various places. Part of the document also appears to be targeted to controversies in interpretation of some aspects of the data. In several instances, the committee found that EPA had spent more time in debunking others’ positions than in bolstering its own arguments. Although the draft provides a comprehensive review of the available data, it is not clear whether studies were evaluated case by case or a consistent set of criteria were applied. To ensure consistent and transparent analysis of the data, criteria for identifying, analyzing, and selecting studies should be established in advance to guide the assessment in focusing on the most relevant studies. Study design and methods are the most important factors in study selection. Other fac-
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