Impact/Purpose:

GENERIC RARE OBJECTIVE: The Regional Applied Research Effort (RARE) provides the Regions with a mechanism to address near term research needs through an ORD Laboratory/Center. Any applied research project that a Region identifies and that an ORD laboratory has the expertise to carry out will be considered if the three following conditions are met: 1) projects must be funded through an ORD Laboratory or Center, 2) the project must fall within the defined mission of the selected ORD Laboratory/Center, and 3) proposals must be research-oriented.

Description:

MTBE is a synthetic gasoline additive that has been found in a number of public drinking water systems in California and other states. Several of the highest concentrations have been found in drinking water wells in the City of Santa Monica, CA where levels as high as 610 ppb have been reported. The extensive MTBE contamination continues to be a threat to state drinking water supplies since it is highly soluble in water, does not readily biodegrade, and is not easily remediated or removed from water. MTBE has an objectionable taste and odor at very low levels, which has caused several states to establish drinking water standards ranging from 35 to 200 ppb. The U.S. EPA has an advisory of 20 to 40 ppb to avoid unpleasant taste and smell. This guideline has not been based on the potential human health risk associated with exposure to MTBE in drinking water via the ingestion, inhalation, and/or dermal routes. The human health risks associated with exposure to MTBE in drinking water are not well understood. There is evidence of chronic nephropathy and mortality in rats exposed to relatively high doses during chronic inhalation exposure, while carcinogenicity has not been quantified. Human exposure to MTBE in drinking water is not limited to the ingestion route, but is also possible via inhalation and dermal contact. Based on previous research and human exposure factor data, the maximum potential inhalation exposure is likely to occur while showering, whereas the maximum potential dermal exposure is likely to occur while bathing. Currently, it is unclear which activity and associated MTBE exposure routes pose the greatest risk to human health. However, to date, there has been extensive research related to chemical volatilization from showers to allow for an approximate inhalation dose estimate, but relatively few data are available to do the same for bathing. There have also been several studies that investigated the human uptake of MTBE via the inhalation route. Again, there are little to no data associated with the potential uptake of MTBE through the skin. Previous dermal research has shown significant uptake of other water contaminants (e.g.. chloroform) through the skin as a result of showering and/or bathing, and swimming in a pool. Due to the potentially significant human exposure to MTBE while bathing with contaminated water and the associated data gaps, the proposed research will focus on the following: to measure directly the uptake of MTBE via absorption through the skin and resulting metabolic activity, to measure air concentrations of MTBE and associated physiological parameters to estimate inhalation exposure while bathing, and to assess the relative contribution of inhalation and dermal exposure to MTBE while bathing.

Record Details: