Study: Relationship Between Contact with Tap Water, Trihalomethane Exposure

Skin contact with and inhalation of trihalomethanes (THMs) result in significantly higher blood and exhaled breath concentrations than simply drinking the same tap water, according to a study published in the July issue of Environmental Health Perspectives.

THMs are chemical compounds that form as the result of a reaction between chlorine and natural organic matter in tap water. Elevated levels of THMs have been associated with cancer and adverse reproductive outcomes.

Although the authors emphasize that public health implications should not be inferred from their findings due in part to the small sample size of the study, the new study could help shape future epidemiologic investigations that explore the health effects of THMs in tap water.

In the study, seven participants in two controlled household environments in North Carolina and Texas performed 14 common household water use activities including ingestion of hot and cold tap water beverages, showering, washing clothes, washing hands, bathing, dish washing, and indirect shower steam exposure. Each testing facility was nearly identical in layout. One household had relatively high total THMs in tap water and the other had relatively low total THMs.

The researchers collected reference samples for the water supply, tap water, and ambient air before any water use activities began. They also collected samples of blood and exhaled breath before and after each activity.

Overall, the researchers found relatively high ratios of pre- to post-activity blood and breath THM levels following several activities, particularly those involving showering and bathing. Increased THM levels following dish washing by hand and exposure to shower steam were also notable.

After analysis of the data, the researchers discovered differences in THM concentration based on water temperatures. "All hot water use activities yielded a 2-fold increase in blood or breath THM concentrations for at least one individual. The greatest observed increase in blood and exhaled breath THM concentration in any participant was due to showering (direct and indirect), bathing, and hand dish washing," they wrote.

John R. Nuckols, of the Department of Environmental and Radiological Health Sciences at Colorado State University, was the lead author of the study. Other authors included David L. Ashley, Christopher Lyu, Sydney M. Gordon, Alison F. Hinckley, and Philip Singer. Funding sources for the research as reported by the authors included the National Center for Environmental Health (Centers for Disease Control and Prevention), the American Water Works Association Research Foundation, and the National Institutes of Health, National Cancer Institute, Occupational and Environmental Epidemiology Branch. The article can be accessed at

This article originally appeared in the 07/01/2005 issue of Environmental Protection.

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