Inhalation exposure to THMs from drinking water

Trihalomethanes (THMs) are significant disinfection byproducts (DBPs) in drinking water. To understand the magnitude of exposure to THMs for the people in southern Taiwan, models are used to estimate the inhalation exposure associated with drinking water based on raw water quality. Two parts of the model are used in this study, one for estimating THM concentration from raw water quality, and one for estimating inhalation exposure to people. Important raw water quality parameters, such as TOC, UV254, pH, temperature of a major water treatment plant in southern Taiwan were collected. An empirical THM formation model was then employed to predict the THM concentration at consumer' houses based on the water quality parameters collected. Difference between the predicted results and experimental data were found to be small, indicating that the model is appropriate. The predicted THM concentration distribution was used as an input parameter for the exposure models. Three major activities associated with probable inhalation exposure of THMs, including showering, dish washing and water boiling, were considered in the exposure models. The model results show that the mean inhalation exposure of THMs for showering, dish washing and water boiling are 44.9, 1.7, and 5.7 μg per day, respectively. The total inhalation exposure (summation of the three activities) was found to be comparable with that for ingestion, indicating that inhalation is an important pathway for THM exposure from drinking water.