A Review of Exposure Assessment Methods Utilized in Studies of Disinfection Byproducts (DBPs) and Birth Defects

Abstract

BACKGROUND AND AIM: Epidemiologic studies of disinfection byproducts (DBPs) and birth defects have employed a variety of exposure assessment methods. Because there is 1) no gold standard exposure assessment method for DBPs, and 2) documented variability in exposure based on spatial, temporal, and personal behavior patterns, it is important to compare methods and understand their potential impact on health effect estimates. This question is particularly relevant for studies measuring exposures for developmental outcomes such as birth defects, with a narrow critical window. METHODS: We reviewed epidemiologic studies of DBPs and birth defects published prior to 2021. Information on exposure assessment methods and critical windows of pregnancy captured by exposure assessment was extracted by one author, with quality control by two authors. Data were organized and summarized based on complexity of the method, including their ability to characterize and address temporal or spatial variability and personal water-use patterns. RESULTS:We identified exposure assessment methods utilized in 21 studies of DBPs and birth defects; 6 studies used non-specific DBP indicators, such as water type or disinfection method;17 studies developed spatial, temporal, or spatiotemporal-informed estimates based on data collected by public monitoring systems in conjunction with additional modeling; 7 studies incorporated personal behavior information to help address route-specific exposure; 4 of these incorporated DBP uptake factors. Most studies incorporated 1 or 2 exposure assessment methods, while 5 studies included 3 or more approaches; 14 studies developed exposure estimates based on the critical window for birth defects. CONCLUSIONS:There is heterogeneity in exposure assessment methods among studies of DBPs and birth defects. These methods vary in complexity and capture distinct sources of DBP variation. The choice of metric affects the anticipated magnitude of exposure misclassification. More consistent consideration of spatiotemporal patterns and the critical window of development will improve exposure assessment in future studies. *Abstract does not reflect EPA policy KEYWORDS: Exposures, Exposure assessment, Birth outcomes, Water quality