The chart to the left shows the percentage of each chemical in BTEX. The chemicals are described in detail below.
- Benzene is a typically found in gasoline and petroleum based products such as plastics, paints, detergents, cosmetics and synthetic rubber. The largest single-source of benzene emissions is tobacco smoke, which accounts for 50 percent of the nation's total benzene emissions. Auto exhaust is the second most common source of benzene, emitting 20 percent of the nation's total benzene emissions. Benzene is a known carcinogen, meaning that the Department of Health and Human Services has label it a cancer-causing agent.
- Toluene also naturally occurs in petroleum products and is commonly found in paints, oils, gums and resins. The U.S. Environmental Protection Agency (EPA) has classified toluene as non carcinogenic.
- Ethylbenzene is a fuel additive that can be found in paints and pesticides. Ethylbenzene has been classified as potentially carcinogenic.
- Xylene comes in three forms: meta-xylene, ortho-xylene and para-xylene. Ortho-xylene is the only naturally occurring form of xylene. All three forms can be found in printing, leather and rubber products. The EPA has classified xylene as non carcinogenic.
Known health effects
BTEX can affect human health if it is ingested, inhaled, or absorbed through skin. If BTEX is ingested it is typically done so through groundwater that has been contaminated by spills, storage tank leaks and overfills, and landfills. If water or soil are contaminated by BTEX the water or soil can be decontaminated. Activated carbon filtration removes BTEX from water and BTEX is biodegradable in soil if the conditions are right. BTEX has been shown to cause short-term health effects such as skin irritation, dizziness, tiredness, headaches, loss of coordination, and eye and nose irritation. In the long run, BTEX has been shown to cause kidney, heart and liver problems, leukemia and cancers in blood-forming organs. 
- United States Geological Survey, “BTEX,” accessed January 23, 2014
- Society of Petroleum Engineers, “Hydraulic Fracturing 101: What Every Representative, Environmentalist, Regulator, Reporter, Investor, University Researcher, Neighbor and Engineer Should Know About Estimating Frac Risk and Improving Frac Performance in Unconventional Gas and Oil Wells,” accessed January 30, 2014
- Ohio Bureau of Environmental Health, "BTEX," January 12, 2014
- Maryland Department of the Environment, "BTEX," February 12, 2007