MTBE (methyl tertiary-butyl ether) is a volatile organic chemical that is commonly used as a fuel additive. It was first added to gasoline in the late 1970’s to improve engine performance and increase the octane rating of the gasoline. In 1995, as part of the Clean Air Act, MTBE levels in gasoline were increased by up to 15% in order to reduce emissions of carbon monoxide.
MTBE occurrence in drinking water can be due to leaks in underground and above ground petroleum storage tanks and pipelines. MTBE is a small molecule that is soluble in water, which allows it to move rapidly into groundwater.
MTBE falls into the category of volatile organic chemicals, or VOCs. Most of Acton’s wells are treated for VOCs by air stripping, which allows these chemicals to evaporate out of the water. In addition, land use restrictions within the zone of influence (Zone II) of each well control the use of MTBE.
Studies on the health effects of MTBE are limited. Short-term effects of high levels of MTBE in drinking water may include nausea, headache and drowsiness. There have been no studies on the long-term effects of MTBE on humans. In animal studies, short-term exposure has been shown to cause kidney problems. The long-term effects of MTBE in animals include increased tumor incidence as well as cancer. However, in many of these studies, MTBE was introduced directly into the stomach and at levels thousands of times greater than the levels typically found in drinking water. Ingestion of high levels of MTBE in drinking water should be rare, because at relatively low levels (well below those that may cause a health concern) MTBE will pose an objectionable taste and odor to most people.
Currently, MTBE is on the drinking water Contaminant Candidate List, where it will be further evaluated to determine if it should be regulated by the Safe Drinking Water Act. The Environmental Protection Agency has issued a Drinking Water Advisory Range of 20 to 40 micrograms per liter (ug/L), based on aesthetic reasons, such as taste and odor. The Massachusetts Department of Environmental Protection has adopted a Guideline (non-enforceable level) of 70 ug/L for MTBE. Exposure to water with levels of MTBE less than 70 ug/L should not cause any adverse health effects.