NTP conducts scoping reviews to identify, categorize, and summarize the literature-based evidence evaluating whether exposure to environmental substances (e.g., chemicals, physical agents, and mixtures) may be associated with adverse health effects. These reviews serve as a foundational step in directing potential further inquiry by identifying areas that are data rich or data poor on project-specific key concepts such as: exposures, health effects, mechanisms, experimental model or study design, and evidence stream (human, experimental animal, in vitro models); however, they do not include a synthesis of the data. Depending on the goals and the available evidence, scoping reviews may include: (1) a summary of the research relating to specific questions or relatively broad topic areas, (2) a systematic evidence map—an interactive visual display of research relating to relatively broad topic areas that can be sorted, filtered, and categorized to illustrate the extent and types of evidence, or (3) both.

NTP conducts these health effects evaluations following the first three steps of the general methods outlined in the “Handbook for Conducting a Literature-Based Health Assessment Using the OHAT Approach for Systematic Review and Evidence Integration” ^†: (1) problem formulation, (2) literature search and selection of studies for inclusion, and (3) abbreviated data extraction to categorize published research by key concepts relevant to the goals of the review. The key feature in applying the systematic review approach to scoping reviews is the application of a transparent framework to document the methods.

^†OHAT is the abbreviation for Office of Health Assessment and Translation, which is within the Division of the National Toxicology Program at the National Institute of Environmental Health Sciences.