Abstract
Evidence-based methodology, in particular systematic review, is increasingly being applied in environmental, public, and occupational health to increase the transparency, comprehensiveness, and objectivity of the processes by which existing evidence is gathered, assessed, and synthesized in answering research questions. This development is also changing risk assessment practices and will impact the assessment of uncertainties in the evidence for risks to human health that are posed by exposure to chemicals. The potential of evidence-based methodology for characterizing uncertainties in risk assessment has been widely recognized, while its contribution to uncertainty reduction is yet to be fully elucidated. We therefore present some key aspects of the evidence-based approach to risk assessment, showing how they can contribute to the identification and the assessment of uncertainties. We focus on the pre-specification of an assessment methodology in a protocol, comprehensive search strategies, study selection using predefined eligibility criteria, critical appraisal of individual studies, and an evidence integration and uncertainty characterization process based on certainty of evidence frameworks that are well-established in health care research. We also provide examples of uncertainty in risk assessment and discuss how evidence-based methodology could address those. This perspective, which neither claims to be comprehensive nor complete, is intended to stimulate discussion of the topic and to motivate detailed exploration of how evidence-based methodology contributes to characterization of uncertainties, and how it will lead to uncertainty reduction in the conduct of health risk assessment.
Highlights
ObjectivesThis handbook describes the methods and considerations for conducting a literature-based review of an agent, substance, mixture, or exposure circumstance selected for evaluation for listing in the Report on Carcinogens (RoC)
The evaluation of other relevant data considers whether there are convincing data demonstrating biologically plausible mechanisms or modes of action for cancer end points reported in humans and/or in experimental animals, or compelling data that the agent acts through mechanism(s) that do not operate in humans
The mechanisms by which a substance causes cancer are not completely known; mechanistic data have played a major role in the listing of several substances in the RoC
Summary
This handbook describes the methods and considerations for conducting a literature-based review (i.e., cancer hazard evaluation) of an agent, substance, mixture, or exposure circumstance (collectively referred to as “substance”) selected for evaluation for listing in the Report on Carcinogens (RoC). The cancer hazard evaluation is captured in a RoC monograph, and this handbook serves as a resource for those preparing the monographs, including Office of the RoC (ORoC) staff, contractor support staff, and technical advisors. The approach to conducting the cancer hazard evaluation incorporates principles of systematic review, with the goal of increasing transparency (to the public and others) on how the conclusions are reached and strengthening consistency across evaluations of different substances. For each substance under review, a protocol is developed that adapts these methods for scientific issues specific to the substance
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