MTBE

Reformulated gasoline; leaks from underground storage tanks and pipelines; fuel spills and boat engines; vehicle exhaust and vapors [1][2].

Breathing gasoline fumes while refueling, in traffic, or from attached garages; drinking contaminated private well water; inhaling vapors released during showering with contaminated water [1][2].

Short-term exposure can cause headache, dizziness, and eye/skin/airway irritation; high levels can affect the nervous system [1]. MTBE spreads quickly in groundwater and causes strong taste/odor at very low levels; there is no federal drinking-water standard [2]. IARC finds human cancer evidence inadequate (Group 3: not classifiable) [3].

Gas station attendants, fuel transport/workers and mechanics; people near leaking tanks, marinas, or heavy traffic; private well users; homes with attached garages [1][2].

Avoid breathing vapors when pumping gas (don’t top off, stand upwind, tighten the cap); ventilate attached garages; fix fuel leaks; test private wells near stations/marinas; use alternative water or an NSF-certified filter shown to reduce MTBE if contamination is found; follow local advisories [1][2].