Estimation of absorption of aromatic hydrocarbons diffusing from interior materials in automobile cabins by inhalation toxicokinetic analysis in rats

Aromatic hydrocarbons, as well as aliphatic hydrocarbons, diffusing from interior materials in automotive cabins are the most common compounds contributing to interior air pollution. In this study, the amounts of seven selected aromatic hydrocarbons absorbed by a car driver were estimated by evaluating their inhalation toxicokinetics in rats. Measured amounts of these substances were injected into a closed chamber system containing a rat, and the concentration changes in the chamber were examined. The toxicokinetics of the substances were evaluated on the basis of the concentration–time course using a nonlinear compartment model. The amounts absorbed in humans at actual concentrations in automobile cabins without ventilation were extrapolated from the results obtained from rats. The absorbed amounts estimated for a driver during a 2 h drive were as follows (per 60 kg of human body weight): 30 µg for toluene (interior median concentration, 40 µg m^?3 in our previous study), 10 µg for ethylbenzene (12 µg m^?3), 6 µg for o‐xylene (10 µg m^?3), 8 µg for m‐xylene (11 µg m^?3), 9 µg for p‐xylene (11 µg m^?3), 11 µg for styrene (11 µg m^?3) and 27 µg for 1,2,4‐trimethylbenzene (24 µg m^?3). Similarly, in a cabin where air pollution was marked, the absorbed amount of styrene (654 µg for 2 h in a cabin with an interior maximum concentration of 675 µg m^?3) was estimated to be much higher than those of other substances. This amount (654 µg) was approximately 1.5 times the tolerable daily intake of styrene (7.7 µg kg^?1 per day) recommended by the World Health Organization. Copyright © 2010 John Wiley & Sons, Ltd.