An ad hoc committee of the National Academies of Sciences, Engineering, and Medicine will consider frameworks for integrating, documenting, and evaluating scientific evidence to assess causality of health and welfare effects by air pollutants as part of National Ambient Air Quality Standards (NAAQS) reviews conducted by the Environmental Protection Agency (EPA). The committee will

• Describe and assess available methods and frameworks for inferring causality of health or welfare effects within a NAAQS review. Based on those assessments, suggest how the number and description of causality categories in the hierarchy to classify the weight of evidence for causation (i.e., causal determinations) might be refined for more effective use in EPA’s Integrated Science Assessments (ISAs) that are prepared for NAAQS reviews. Indicate if those categories are necessarily mutually exclusive in making causal determinations from a body of evidence, and, if appropriate, identify methods to characterize the degree of confidence in a causal determination.

• Assess new advances for integrating and evaluating scientific evidence to inform causal determinations critical to EPA’s NAAQS reviews. Suggest emerging tools and approaches that might be used in the near and longer-term to integrate and synthesize evidence across studies and scientific disciplines. In addition, consider whether those tools and approaches might be used to assess consistency among independent studies within a discipline, coherence across different lines of evidence, and evidence of biological plausibility.

• Identify additional issues concerning potential confounders (i.e., other factors associated with both the pollutant and the effect) that EPA might consider when assessing causality for an individual criteria pollutant that is part of an atmospheric complex pollutant mixture.

The committee’s report will describe, in the context of ISAs, the types and characteristics of evidence most useful for forming a causal determination, and whether a single framework and practices related to it for assessing causality may be applied to both health and welfare effects. The report will make recommendations related to the development and use of ISA frameworks for causal determinations and describe priority research needed to improve those frameworks in the future.