EPA has classified toluene as a Group D, not classifiable as to human carcinogenicity . Exceedance of the RfC does not imply that an adverse health effect would necessarily occur. As the amount and frequency of exposures exceeding the RfC increase, the probability of adverse health effects also increases. The deliberate inhalation of paint or glue may produce high levels of exposure to toluene, as well as to other chemicals, in solvent abusers. Toluene exposure may also occur in the workplace, especially in occupations such as printing or painting, where toluene is frequently used as a solvent.
Automobile emissions are the principal source of toluene to the ambient air.
Toluene may also be released to the ambient air during the production, use, and disposal of industrial and consumer products that contain toluene. Metabolites measured in the urine are not specific to toluene, and testing must occur within 12 hours of exposure. CNS depression and death have occurred at higher levels of exposure. Cardiac arrhythmia has also been reported in humans acutely exposed to toluene. Constriction and necrosis of myocardial fibers, swollen liver, congestion and hemorrhage of the lungs, and tubular kidney necrosis were also reported.