Toluene is a member of the benzene, toluene, ethylbenzene, and xylene (BTEX) group of pollutants, which are volatile organic compounds (VOCs). VOCs are certain compounds that participate in atmospheric photochemical reactions; in other words, VOCs aid in smog and ground-level ozone formation. Though VOCs are released by plants, they are released in much greater quantities by anthropogenic sources. Toluene is a component of paint thinners, adhesives, some inks, rubber, pesticides, and nail polish, is an additive to gasoline, and is used in leather tanning. It most commonly enters surface or groundwater through petroluem spills, which accounted for 90 percent of all toluene spills in 1993. Additionally, the EPA found that the pollutant was present in the water or soil at 63 percent of domestic hazardous waste sites in 1991.
Fish and other aquatic organisms are sensitive to both acute and chronic toluene exposure, which can cause major nervous system and neurological damage. Toluene is also most hazardous when absorbed through the skin, which is the most common point of entry for aquatic organisms.