Household exposures to drinking water disinfection by-products: whole blood trihalomethane levels

Exposure to drinking water disinfection by-products (DBPs), such as trihalo methanes (THMs), has been associated with bladder and colorectal cancer in humans. Exposure to DBPs has typically been determined by examining histori cal water treatment records and reconstructing study participants' water co nsumption histories. However, other exposure routes, such as dermal absorpt ion and inhalation, may be important components of an individual's total ex posure to drinking water DBPs. In this study, we examined individuals' expo sure to THMs through drinking, showering, or bathing in tap water. Thirty-o ne adult volunteers showered with tap water for 10 min ( n = 11), bathed fo r 10 min in a bathtub filled with tap water ( n = 10), or drank 11 of tap w ater during a 10-min time period (n = 10). Participants provided three 10 m i blood samples: one sample immediately before the exposure; one sample 10 min after the exposure ended; and one sample 30 min ( for shower and tub ex posure) or 1 h ( for ingestion) after the exposure ended. A sample of the w ater ( from the tap, from the bath, or from the shower) was collected for e ach participant. We analyzed water samples and whole blood for THMs (bromof orm, bromodichloromethane, dibromochloromethane, and chloroform) using a pu rge-and-trap/gas chromatography/mass spectrometry method with detection lim its in the parts-perquadrillion range. The highest levels of THMs were foun d in the blood samples from people who took 10-min showers, whereas the low est levels were found in the blood samples from people who drank 11 of wate r in 10 min. The results from this study indicate that household activities such as bathing and showering are important routes for human exposure to T HMs.