Gasoline vapors may contain methyl tert-butyl ester (IUPAC name 2-Methoxy-2-methylpropane). Worldwide production of "MTBE" has been constant at about 18 million tons/y (2005) owing to growth in Asian markets which are less subject to ethanol subsidies.)
(Another in series "If cars came with warning labels.")
Per that Wicked Pee thingee:
"In one case, the cost to oil companies to clean up the MTBE in wells belonging to Santa Monica is estimated to exceed $200 million. In another case, the City of New York estimated a $250 million cost for cleanup of a single wellfield in Queens, NY. More recently, a jury awarded the State of New Hampshire $236 million in damages in order to treat groundwater contaminated by MTBE."