For nearly a century, public water supplies have been treated with disinfectants to reduce or eliminate the risk of waterborne microbes. The most widely used disinfectant is chlorine, which reacts readily with organic matter to produce byproducts, including the suspected human carcinogen chloroform. Thus, although chlorine reduces microbial risks, it creates new potential health risks. Battelle, under the auspices of the U.S. Environmental Protection Agency’s (EPA) National Exposure Research Laboratory, recently completed a study of chloroform exposure while bathing.

Most humans in the United States are exposed to low levels of chloroform through ingestion, inhalation, or dermal contact. Bathing or showering can expose a person to chloroform via all three exposure routes. Studies have suggested that significant dermal exposure to chloroform occurs while showering. This dose is roughly comparable to that resulting from inhalation.

Battelle’s research indicates that water temperature exerts a strong effect on dermal absorption of chloroform while bathing or showering. Subjects bathed or showered in contaminated water while they breathed pure air through a face mask, and the chloroform in their exhaled breath was measured rapidly and continuously. Breath measurements can be used to estimate chemical exposure and detect changes in the concentration of chemicals in the blood with time because of the dynamic equilibrium between the concentration of a compound in the blood and its concentration in exhaled breath.

Among 10 subjects who participated in the bathing study, the mean amount of chloroform exhaled at the lowest bath-water temperature (30ºC) was 0.2 µg, while at the highest temperature (40ºC) it was 7 µg, a factor increase of more than 30. Virtually no chloroform was absorbed at 30ºC and the average maximum observed breath concentration was 3 µg/m³; this value increased to 45 µg/m³ at 40ºC.

The increase is explained by the heat management mechanisms of the body. At low water temperatures, the capillaries closest to the skin’s surface are assumed to undergo decreased blood flow, forcing the chloroform to diffuse across a greater distance to reach the blood. At high water temperatures, the opposite occurs. Shower experiments, conducted separately, showed essentially the same temperature effects.

The study made use of Battelle-developed breath measurement technology to monitor dermal exposure in real time. Measurements were made using a specially designed breath inlet device attached to a compact, commercially available mass spectrometer. The system allows for the measurement of a chemical at concentrations as low as one or two parts per billion in as little as 4 or 5 seconds. The technique is currently in use at Battelle in a separate EPA-sponsored study to determine dermal and inhalation exposure to the fuel additive methyl tert-butyl ether (MTBE).

For more information please contact Sydney M. Gordon at (614) 424-5278, gordon@battelle.org.