Subchronic Exposure to Regulated Trihalomethanes and Haloacetic Acids: Do We Need to Refine Our Exposure Assessment? A Full-Scale Case Study in a Canadian Municipality.

Regulated disinfection byproducts (e.g., trihalomethanes and haloacetic acids) in drinking water networks fluctuate spatially and temporally, depending on water sources and treatment practices with higher concentrations during the summer. Trihalomethanes and haloacetic acids monitoring is based on yearly averages of quarterly measurements with maximum acceptable concentrations where extensive monitoring of disinfection byproducts is not required during those months. Because of concerns that exposures of a short duration could result in adverse reproductive and developmental outcomes, it is vital to study the temporal and spatial variations in exposure within complex systems such as networks. This paper uses an extensive data set in a network to study how domestic exposure may vary across the network and influence potential health risk estimation for key lifestages such as infants, toddlers, and adults. According to this study, the patterns and levels of subchronic exposure to those compounds vary spatially in the network. Subchronic hazard quotients to chloroform were also investigated and were below one, indicating that levels of exposure are less than the dose that may trigger toxicity for the selected end point. The information provided may assist public health authorities in evaluating the influence of DBP peaks on exposure and subchronic hazard quotients as well as in identifying areas of a distribution system with higher subchronic risks than others.