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Keywords:

  • driver;
  • air pollution;
  • environmental contaminants;
  • extrapolation;
  • closed chamber system

Abstract

The interior air of an automobile cabin has been demonstrated in our previous studies to be contaminated by high concentrations of a large variety of aliphatic hydrocarbons diffusing from the interior materials. In the present study, the amounts of seven selected aliphatic hydrocarbons absorbed by the car driver were estimated by evaluating their inhalation toxicokinetics in rats. Measured amounts of the substances were injected into a closed chamber system in which a rat had been placed, and the concentration changes in the chamber were examined. The toxicokinetics of the substances were evaluated based on concentration–time courses using a nonlinear compartment model. Their absorption amounts in humans at the levels of actual concentrations in the cabins without ventilation were extrapolated from the results found with the rats. The absorption amounts estimated for a driver during a 2 h drive were as follows: 6 µg/60 kg of human body weight for methylcyclopentane (interior concentration 23 µg/m3 as median value in previous study), 5 µg for 2-methylpentane (36 µg/m3), 13 µg for n-hexane (65 µg/m3), 51 µg for n-heptane (150 µg/m3), 26 µg for 2,4-dimethylheptane (97 µg/m3), 17 µg for n-nonane (25 µg/m3) and 49 µg for n-decane (68 µg/m3). An inverse relationship was found between the exposure and absorption among the substances (e.g. between n-decane and 2,4-dimethylheptane). These findings suggest that not only the exposure concentrations but also the absorption amounts should be taken into account to evaluate the health effects of exposure to low concentrations of volatile compounds as environmental contaminants. Copyright © 2009 John Wiley & Sons, Ltd.