Unlike ethanol, MTBE can be shipped through existing pipelines, and its volatility is lower, making it easier to meet the emission standards. To address its unique air pollution problems, California has adopted similar, but more stringent requirements for its gasoline California RFG.
What are the air quality benefits of using reformulated gasoline RFG that contains oxygenates? RFG has been helping improve the air for millions of Americans since The use of RFG compared to conventional gasoline has resulted in annual reductions of smog-forming pollutants volatile organic compounds and nitrogen oxides and toxics such as benzene. Refiners are required to reduce the emissions of volatile organic compounds, toxics, and nitrogen oxides by 27, 22, and 7 percent, respectively, compared to the conventional gasoline they produced in A growing number of studies have detected MTBE in ground water throughout the country; in some instances these contaminated waters are sources of drinking water.
Low levels of MTBE can make drinking water supplies undrinkable due to its offensive taste and odor. The majority of the human health-related research conducted to date on MTBE has focused on effects associated with the inhalation of the chemical. When research animals inhaled high concentrations of MTBE, some developed cancers or experienced other non-cancerous health effects To date, independent expert review groups who have assessed MTBE inhalation health risks e. However, researchers have limited data about what the health effects may be if a person swallows ingests MTBE.
EPA's Office of Water has concluded that available data are not adequate to estimate potential health risks of MTBE at low exposure levels in drinking water but that the data support the conclusion that MTBE is a potential human carcinogen at high doses. Recent work by EPA and other researchers is expected to help determine more precisely the potential for health effects from MTBE in drinking water. EPA reviewed available health effects information on MTBE in its Drinking Water Advisory guidance and decided that there was insufficient information available to allow EPA to establish quantitative estimates for health risks and as such would not set health advisory limits.
The drinking water advisory document indicates that there is little likelihood that MTBE in drinking water will cause adverse health effects at concentrations between 20 and 40 ppb or below.
EPA will issue a secondary drinking water standard, based on taste and odor, by late Fall This taste and odor standard will serve as a guideline that states may adopt. In December , EPA issued a Drinking Water Advisory that states concentrations of MTBE in the range of 20 to 40 ppb of water or below will probably not cause unpleasant taste and odor for most people, recognizing that human sensitivity to taste and odor varies widely.
The advisory is a guidance document that recommends keeping concentrations below that range. EPA also reviewed the available information on health effects in the advisory and stated that there is little likelihood that MTBE concentrations between 20 and 40 ppb in drinking water would cause negative health effects.
As a means of gathering occurrence information, beginning in , EPA will require all large drinking water systems and a representative sample of small systems to monitor and report the presence of MTBE Unregulated Contaminant Monitoring Regulation. Though you cannot currently purchase a home testing kit, you can determine if your water contains MTBE the following ways.
If your drinking water is supplied by a public water system, you can contact the system directly and ask whether they monitor for MTBE and what levels, if any, have been detected.
In , most public water systems will be required to monitor for MTBE. If you have a private well, you may want to have your well water tested. Your local health department may be able to tell you if MTBE has been found in water in your area. There are opportunities for MTBE to leak into the environment and potentially get in drinking water sources wherever gasoline is stored, and there are opportunities for it to be spilled whenever fuel is transported or transferred.
While federal and state programs minimize the potential for leaks and spills, no system is foolproof. Contamination of drinking water sources can occur from leaking underground and above ground fuel storage tanks, pipelines, refueling spills, automobile accidents damaging the fuel tank, consumer disposal of "old" gasoline", emissions from older marine engines, and to a lesser degree, storm water runoff, and precipitation mixed with MTBE in the air EPA's Office of Ground Water and Drinking Water or USGS report.
Although there are no nation-wide data sets from which to fully characterize MTBE contamination of water, a growing number of studies to-date have detected MTBE in drinking water supplies throughout the country. Current data on MTBE levels in ground and surface waters indicate widespread and numerous detections at low levels of MTBE, with a more limited number of detections at higher levels only about 1 percent of concentrations are more than 20 parts per billion ppb as discussed in the Blue Ribbon Panel Report on Oxygenates in Gasoline.
Studies have shown that MTBE is detected in water roughly five times more often and at higher concentrations in areas of the country where federal RFG is sold i. However, releases from petroleum storage tanks, and pipeline breaks or other point sources can cause high concentrations of MTBE in water.
In , the city of Santa Monica learned that two of its drinking water wellfields, Charnock and Arcadia, were contaminated with MTBE at levels as high as ppb and 86 ppb respectively.
In response, the two wellfields, representing 50 percent of the city's drinking water supply were shut down and the city began purchasing replacement water. This incident was the first major water contamination which brought public attention to MTBE. Site-specific clean-up is underway. Because MTBE dissolves easily in water and does not "cling" to soil very well, it migrates faster and farther in the ground than other gasoline components, thus making it more likely to contaminate public water systems and private drinking water wells.
MTBE does not degrade breakdown easily and is difficult and costly to remove from ground water. MTBE is generally more resistant to natural biodegradation than other gasoline components. Some monitoring wells have shown little overall reduction in MTBE concentration over several years which suggests that MTBE is relatively persistent in ground water. Animal studies involving high doses of MTBE have shown effects such as skin and eye irritation.
Biomonitoring studies of blood MTBE can provide physicians and public health officials with reference values so that they can determine whether people have been exposed to higher levels of MTBE than the levels found in the general population.
Biomonitoring data can also help scientists plan and conduct research on exposure and health effects. Skip directly to site content Skip directly to page options Skip directly to A-Z link. National Biomonitoring Program. Section Navigation. Facebook Twitter LinkedIn Syndicate.
At room temperature, MTBE is a volatile, flammable and colorless liquid that dissolves rather easily in water. MTBE had been used in U. Between and , MTBE had been used at higher concentrations in some gasoline to fulfill the oxygenate requirements set by Congress in the Clean Air Act Amendments. A few cities, such as Denver, used oxygenates MTBE at higher concentrations during the wintertime in the late 's. Oxygen helps gasoline burn more completely, reducing harmful tailpipe emissions from motor vehicles.
In one respect, the oxygen dilutes or displaces gasoline components such as aromatics e. In another, oxygen optimizes the oxidation during combustion. Most refiners have chosen to use MTBE over other oxygenates primarily for its blending characteristics and for economic reasons.
Refiners could choose to use other oxygenates, such as ethanol. The two oxygenated gasoline programs were:.
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