New York Times

New York State environmental officials last year compiled an internal list of more than 1,500 places where soil or water had been contaminated with M.T.B.E., a gasoline additive that makes water taste like turpentine and is a possible cause of cancer and other health problems.

The tally of M.T.B.E. sites is more than three times the number reported publicly in the state's toxic-spills database, which real estate buyers and suppliers of drinking water use to spot contamination problems.

A GASOLINE additive intended to reduce air pollution, in large-scale use on Long Island for less than 10 years, is rapidly moving though the region's groundwater, penetrating drinking water supplies.

The additive, M.T.B.E., for methyl tertiary butane ether, has been found in the highest concentrations in shallow wells near gas stations and industrial areas where petroleum spilled. It is also being detected in nearly one in five of the deeper public wells that are the Island's principal sources of drinking water.