Toluene is a liquid that occurs in petroleum and is a constituent of gasoline. Toluene can also be manufactured from other chemicals or in the process of baking coal to produce coke. Toluene has been used in a wide variety of products like paint, lacquer, rubber, paint thinners, glues, and fingernail polish, and to make other chemicals like nylon, plastics, and TNT.
Environmental Fate and Transport
Toluene evaporates quickly, so much of the toluene that is released to the environment ends up in the atmosphere or indoor air (e.g., when using products that contain toluene inside buildings). Toluene released to the ground may partially evaporate, but some may also move through the soil until it reaches groundwater. Because toluene is somewhat soluble in water, it can travel with groundwater as groundwater flows. Leaking underground storage tanks at gas stations are a common source of toluene (and other chemicals) in groundwater. There are microorganisms in the soil that can break down toluene, but this process often takes a long time, and toluene can persist in groundwater for years.
Most toluene exposure occurs via breathing vapors from products containing toluene. Exposure can also occur from drinking groundwater that has toluene dissolved in it. Workers in facilites that use toluene, smokers, and persons who intentionally breathe toluene-containing solvent to get high are likely to experience higher exposures. Persons who live in or near places where toluene has been released or disposed of may also experience higher exposures.
Some of the toluene that a person breathes may be breathed out as they exhale, but some will likely be absorbed into their bloodstream. Some of the toluene that a person touches may enter their body and enter their bloodstream. Toluene that a person ingests will likely be absorbed by their digestive tract and end up in their bloodstream. Our bodies usually break down toluene quickly and excrete the breakdown products within a day or so, but some of it may be stored in body fat.
Health effects from toluene exposure depend, among other things, on the dose and duration of exposure. There are many possible exposure effects, including but not limited to dizziness, headache, loss of consciousness, vision and hearing problems, loss of coordination, and confusion or even death. Exposure to high levels of toluene during pregnancy may affect subsequent development of children. Exposure to other chemicals or drugs at the same time that exposure to toluene occurs may produce different or more severe effects, and many of those interactions are not well understood. Studies in workers and animals exposed to toluene generally indicate that toluene is not carcinogenic (cancer-causing).
The preceding paragraphs are summarized from the Public Health Statement for Toluene published by the Agency for Toxic Substances and Disease Registry.
Additional Cancer Assessments
U.S. EPA's Integrated Risk Information System states that there is inadequate evidence to assess toluene's carcinogenic potential.
Toluene does not appear in the National Institute of Health's Report on Carcinogens (15th Edition).
The International Agency for Research on Cancer has determined that "Toluene is not classifiable as to its carcinogenicity to humans", and "There is inadequate evidence in humans for the carcinogenicity of toluene", and "There is evidence suggesting lack of carcinogenicity of toluene in experimental animals". (IARC, page 855).