Total trihalomethanes (TTHMs) and other disinfection byproducts (DBPs) have been a concern in Flint, Michigan, in both delivered water and water from home water heaters. Historical TTHM data and DBP sampling results from Flint were combined with models for predicting hot water TTHMs to assess the probability of certain DBP concentrations. Results were compared with hot and cold water DBPs from a water system in Florida. Flint results were used to estimate cancer risk resulting from chronic exposure to hot water TTHMs, and compared to similar risk assessments in other water systems. Results indicate TTHM concentrations decreased in Flint following a return to water from the Detroit Water and Sewerage Department, and were very near the mean value for public drinking water systems in the United States. Measurement of other unregulated DBPs also indicated levels within the typical ranges. Monte Carlo simulations coupled with modeling of hot water TTHMs indicated a low probability of TTHMs exceeding 80 μg/L in Flint in 2016. The estimated cancer risk from exposure to TTHMs in Flint is similar to other areas. The methods used in this work can apply broadly to other water systems to de-escalate perceptions of risk following a water crisis
