Health Risk Issues Related to MTBE in Drinking Water
Despite the attention given to methyl tertiary butyl ether (MTBE) as a contaminant in ground water and surface water, the implications of such contamination for human health have not been clearly established to date. Limitations in the databases for both exposure and health effects have contributed to this situation. Systematic monitoring and probabilistic sampling of drinking water for MTBE contamination have been limited thus far, and therefore an accurate assessment of the potential for population exposures to MTBE has been difficult to make. Further complicating attempts to assess exposure potential is the possibility that the taste and odor characteristics of MTBE could reduce the likelihood of exposure, although the actual impact of taste and odor on water consumption has not been well documented. With respect to health effects, a substantial database on the inhalation toxicity of MTBE exists, but much less information has been available regarding the effects of MTBE by the oral route, particularly in drinking water. Available pharmacokinetics information now makes it possible to extrapolate from inhalation toxicity data in rodents to estimate health hazards of MTBE via the oral route in humans. However, several issues complicate the interpretation of MTBE health effects. These issues are currently being examined as part of the development of a cancer assessment and oral reference dose (RfD) by the U.S. Environmental Protection Agency. This presentation highlights and summarizes the foregoing topics, but it also offers a reminder that the potential health risks associated with MTBE in drinking water need to be considered ultimately in the broader context of a comparative evaluation of the full life-cycle environmental impacts of different fuel options, not just MTBE alone.