Changes in blood trihalomethane concentrations resulting from differences in water quality and water use activities.

Water disinfection is extremely important for the protection of public health; however, it also forms by-products, including trihalomethanes (THMs). Previous studies of health effects from disinfection by-products have lacked accurate methods to quantify exposure over time. As a first step in establishing a better system for exposure assessment, the authors investigated which household water use activities cause a significant increase in internal dose concentrations of THMs. In this study, 7 subjects in 2 different cities carried out 12 common activities that involved water use. In 3 of these activities-bathing, showering, and washing dishes by hand-the blood concentrations of THMs increased substantially. Further analysis of the data suggested that tap water concentrations primarily controlled the blood concentrations from bathing exposure, whereas tap water concentrations and ambient air concentrations resulting from water use affected the blood concentrations from showering exposure. Further studies will focus on variables in these activities that can alter exposure.