Benzene and its methyl-derivatives: Derivation of maximum exposure levels in automobiles

Automobile drivers are exposed to several organic hydrocarbons. Concentrations measured in passenger compartments have been reported to range between 13 and 560 μg/m3 for benzene, 33-258 μg/m3 for toluene, 20-250 μg/m3 for xylene (mixed isomers) and 3-23 μg/m3 for trimethylbenzene (mixed isomers). These aromatic hydrocarbons are emitted from gasoline and from materials inside a car. In the present study we evaluated, whether these exposures pose a potential risk to the health of drivers. Therefore, we derived maximum exposure levels inside cars for chronic (ELIAchronic) and short-term (STELIA) exposure. The lowest ELIA'schronic for benzene, toluene, xylene and trimethylbenzene were 0.083, 1.2, 8.8 and 0.31 mg/m3, respectively. The respective STELIA's were 16, 30, 29 and 25 mg/m3. Obviously concentrations of toluene, xylene and trimethylbenzene inside cars do not exceed their individual STELIA's. In contrast, benzene seems to be problematic, since concentrations inside cars amount up to 0.56 mg/m3, which exceeds the ELIAchronic derived for benzene. This should not be underestimated, since benzene is a genotoxic carcinogen that probably acts by non-threshold mechanisms. In conclusion, concentrations of toluene, xylene and trimethylbenzene usually observed inside cars are unlikely to pose a risk to the health of drivers. A systematic toxicological evaluation of the risk associated with benzene exposure in cars seems to be necessary.