Investigators found two metabolites (break-down products) of MTBE in men who volunteered to inhale small quantities of the additive. Throughout the world, MTBE is combined with gasoline to add extra oxygen, which makes fuel burn more cleanly and reduces air pollution. While the implications of the new findings are still unclear, it has been noted that at high exposure levels, MTBE may cause kidney and liver tumors is some laboratory rodents. Headache, nausea, nasal and eye irritation have been reported among humans who live in areas where MTBE-oxygenated gas is used. In 1994, 20.6 million tons of MTBE were produced.

Chemical Research in Toxicology September 20,1999;148:274-280.

COMMENT: Just another example of how we are all exposed to a tremendous amount of chemicals. This risk is clearly related to the population density of the area that you live in and is a strong reason to live in a less densely populated area.