Review of EPA's Integrated Risk Information System (IRIS) Process (2014) / Chapter Skim
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Pages 3-9
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From page 3... ...
Like other NRC committees that had reviewed IRIS assessments, the formaldehyde committee identified deficiencies in the specific assessment and more broadly in some of EPA's general approaches and specific methods. Although the committee focused on evaluating the IRIS formaldehyde assessment, it provided general suggestions for improving the IRIS process and a roadmap for its revision in case EPA decided to move forward with changes to the process.
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From page 4... ...
Therefore, the committee found the term evidence integration to be more useful and more descriptive of the process that occurs after completion of systematic reviews. GENERAL ISSUES The NRC formaldehyde report made several general recommendations concerning the IRIS process, including improving the clarity of the assessments by rigorous editing to reduce redundancies, inconsistencies, and text volume; describing assessment methods more fully; enhancing quality-control processes for assessments; standardizing review and evaluation approaches; and ensuring appropriate expertise on the various chemical-assessment teams.
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From page 5... ...
First, with the support of an information specialist who is trained in conducting systematic reviews, EPA should perform a broad literature search designed to identify possible health outcomes associated with the chemical under investigation. The broad search should not be confused with the comprehensive literature search that is conducted for evidence identification in a systematic review (see Figure S-1)
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EPA should include protocols for all systematic reviews conducted for a specific IRIS assessment as appendixes to the assessment. EVIDENCE IDENTIFICATION The NRC formaldehyde report provided several suggestions aimed at improving EPA's approach to evidence identification, including establishing standard protocols, developing a template to describe the search approach, and using a database to capture study information and relevant quantitative data.
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From page 7... ...
Whatever approach is adopted, the assessment approach and the results should be fully described and reported in the IRIS assessment. EVIDENCE INTEGRATION FOR HAZARD IDENTIFICATION The NRC formaldehyde committee provided several recommendations regarding evidence integration, including reviewing the use of weight-of-evidence guidelines, standardizing an approach to using them, developing uniform language to describe the strength of evidence on noncancer effects, and providing more integrative and transparent discussions of weight of evidence.
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From page 8... ...
Consequently, the premises and structure of the decision-making process should be as explicit as possible, and the basis for the determination needs to be connected explicitly to the evidence tables produced in the IRIS process. CALCULATION OF TOXICITY VALUES In addition to hazard identification, IRIS assessments typically derive toxicity values -- reference concentrations, reference doses, and unit risks -- that can be used with exposure assessments to derive quantitative risk estimates (see Figure S-1)
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From page 9... ...
Although subjective judgment remains an inherent feature of deriving toxicity values, EPA should develop formal methods for combining the results of multiple studies and selecting the final IRIS values with an emphasis on achieving a transparent and replicable process. EPA could also improve documentation of dose-response information by clearly presenting two dose-response values: a central estimate (such as a maximum likelihood estimate or a posterior mean)
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