Benzene is also a natural component of petroleum. Benzene is found naturally in the environment in low concentrations. It is a component of crude oil and is formed through incomplete combustion of organic materials. Benzene enters water and soil through petroleum seepage and weathering of exposed coal-containing strata. The magnitude of emissions from natural sources is not known but, based on concentrations in rural areas, it is believed to be generally low in comparison to anthropogenic sources.
Vehicle emissions are the major source of benzene released to the environment.
In Canada, the primary source of human exposure to benzene is ambient and indoor air. In this case, a major source is cigarette smoke. Fatalities from human exposure to high concentrations of benzene have been documented since the early 1900s. Since then there has been an increasing focus on the impacts of benzene at ever-lower levels of exposure. A strategy for further reductions, beyond 2000, will be developed through the consultation and analysis process.