The evolving science of systematic review in environmental health decision making

Abstract

Systematic review (SR) methods are increasingly being recommended and used to inform environmental health decisions. SR has the potential for long-term effects on public health, due to improved consistency of evidence review with lower bias. SR have been adapted from clinical medicine, where data is largely from randomized, controlled trials. Environmental health SRs often rely on data from human epidemiological studies to inform the relationship between exposures and adverse health outcomes.To bridge between SR in environmental health and the clinical sciences, authoritative bodies, U.S. agencies, and academic scientists developed and implemented validated, peer-reviewed SR methods including the Navigation Guide and the U.S. National Toxicology Program’s OHAT Approach. In contrast, US EPA under the Toxic Substances Control Act is using a significantly different approach, with potential implications for regulation of hazardous chemicals and public health.While there has been an increase in SR use, there are divergent approaches to key elements of the SR process, in particular assessing the risk of bias in observational design studies and evaluation of the quality of the body of evidence. Areas of concern for risk of bias include use of quantitative scoring methods and exclusion of studies based on one ‘critically deficient’ domain. When evaluating the quality of a body of evidence and synthesizing evidence into normative guidance, approaches in environmental health have adopted elements of GRADE (Grading of Recommendations Assessment, Development and Evaluation). However, there is still discussion about accounting for observational human studies and how to assess magnitude of effect.This presentation will highlight the current challenges associated with evaluating human epidemiological evidence, compare current approaches being used by EPA to validated best practice methods, and discuss important future considerations to ensure that the most important and critical types of evidence to inform environmental health decision making are protected.