Common Contaminants

Most leaking underground storage tank (lust) sites are contaminated by gasoline

Because most leaking underground storage tank (LUST) sites are contaminated by gasoline, the following constituents of gasoline are the typical contaminants of concern of LUST sites.

Benzene, toluene, ethylbenzene, and xylenes (referred to as the BTEX compounds) are the most common hazardous components of gasoline leaks.


Common LUST Contaminants

Benzene is the most hazardous of these compounds — its EPA Maximum Contaminant Level (MCL) is 5 parts per billion (ppb). Long-term exposures to benzene in drinking water at levels above the MCL increase the risk of cancer.

Toluene and ethylbenzene are not considered carcinogenic (cancer-causing). The EPA Maximum Contaminant Level (MCLs) are 1.0 and 0.7 parts per million (ppm), respectively. Over the long term, toluene and ethylbenzene damage the liver, kidneys, and central nervous system.

Xylenes are a mixture of compounds (ortho-, meta-, and para-xylene) with two methyl (-CH3) groups attached to a benzene ring. The EPA Maximum Contaminant Level (MCL) for total xylenes is 10 ppm. Xylenes also affect the liver, kidneys, and nervous system, but they are not considered nearly as hazardous as the first three.