The polemic 
 :In 1995 high levels of MTBE were unexpectedly discovered in the water wells of Santa Monica, California. Subsequent tests found tens of thousands of contaminated sites across the country. MTBE in groundwater is a health risk, and it also ruins the taste of the water even at low concentrations. The leakage problem is attributed to the intrinsic risk of underground tank leakage or fuel spills and to the lack of effective regulations for underground storage tanks. In many states the presence of MTBE is treated much more aggressively than mere fuel contamination, and correspondingly the cleanup costs can be much higher. MBTE is an extremely mobile chemical in groundwater. The fact that the EU does not predict the same problem in Europe may be merely indicative that the EU trails the U.S. in most technology areas of water pollution. . This report for the EU is severely flawed to the extent of laughable. It is self serving to placate the EU continued use of MTBE. Its level of analysis is primitive. For example, it dismisses the California experience with MTBE, saying California does not have sufficient precipitation compared to Europe to flush out the aquifers! 
 I reverted this to the old version, since this text adds a polemic tone to the article. This is not a discussion forum. When it's unknown, an encyclopedia states it's unknown. An encyclopedia doesn't argue for a specific point of view, possibly only mentions it. Some other changes were also made in the article, re-wording towards a political attack on MTBE, but I think that there's no reason to discuss those. Gasoline, especially reformate, contains quantitative amounts of carcinogens such as aromatics.