The state of Pennsylvania has started lawsuits against dozens of oil companies and refiners, accusing them of contaminating groundwater with the gasoline additive methyl tertiary butyl ether (MTBE). The list of almost 50 companies includes some of the biggest oil and gas market players, such as Exxon Mobil, BP and Chevron, according to Bloomberg.

The state is seeking damages that would cover its costs for removing MTBE from groundwater reserves and for monitoring use of the additive. Since 1994 the state has spent approximately $738 million investigating and cleaning up some 3,400 gasoline spills and leaks, with a large number of these involving MTBE, legal documents claimed.

Two of the lawsuits filed in Philadelphia city courts were made public through statements by Attorney General Kathleen Kane and by Gov. Tom Corbett's office of general counsel. According to the Associated Press, the list of defendants includes MTBE producers, gasoline refiners, marketers and distributors which practically controlled the entire state market. The lawsuits claim that by the time these companies promoted gasoline with the additive, more eco-friendly alternatives were already available on the market.

Similar lawsuits have also been launched by New York City, Vermont and New Hampshire. Earlier this year the U.S. Supreme Court upheld a jury's decision that Exxon Mobil should pay a damage award of $104.7 million for contaminating New York City wells with MTBE, Bloomberg reported.