Approach to estimation of absorption of aliphatic hydrocarbons diffusing from interior materials in an automobile cabin by inhalation toxicokinetic analysis in rats

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 microg/60 kg of human body weight for methylcyclopentane (interior concentration 23 microg/m(3) as median value in previous study), 5 microg for 2-methylpentane (36 microg/m(3)), 13 microg for n-hexane (65 microg/m(3)), 51 microg for n-heptane (150 microg/m(3)), 26 microg for 2,4-dimethylheptane (97 microg/m(3)), 17 microg for n-nonane (25 microg/m(3)) and 49 microg for n-decane (68 microg/m(3)). 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.

Influence of the respirator on volatile organic compounds: an animal study in rats over 24 hours

“…Yoshida et al were able to demonstrate an observable absorption amount of 2-methylpentane by inhalation in a rat model based on the knowledge of well-known diffusion from, e.g. interior materials of an automobile cabin [39]. This supports our presumption of classifying 2-methylpentane as a 'resorbed VOC'.…”

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

“…Therefore, the amounts of aromatic hydrocarbons absorbed were suggested to show a tendency to increase with the number of carbon atoms. We also previously obtained similar results in an inhalation toxicokinetic study of rats exposed to some aliphatic hydrocarbons, that is, n-hexane (C6) < n-heptane (C7) < n-nonane (C9) < n-decane (C10) (Yoshida, 2010).…”

“…In our previous study (Yoshida, 2010), the absorbed amounts of n-heptane (C7), 2,4-dimethylheptane (C9), and n-nonane (C9) were estimated to be 2.3, 1.7 and 3.5 mg kg -1 of body weight, respectively, in rats exposed at a concentration of 50 mg m -3 for 2 h. The absorbed amounts of toluene (C7) or 1,2,4-trimethylbenzene (C9) were estimated to be higher than those of n-heptane (C7) or 2,4-dimethylheptane and n-nonane (C9), respectively, in rats exposed at the same concentration (Table 2). Therefore, among hydrocarbons with the same number of carbon atoms, aromatics were considered to be absorbed more easily than aliphatics.…”

“…The aim of the present study was to estimate the amounts absorbed by the driver of an automobile by examining the inhalation toxicokinetics of the seven aromatics in rats to obtain basic data for evaluating the health effects of exposure to the hydrocarbons on drivers, in conjunction with our previous results from a study on the aliphatic hydrocarbons (Yoshida, 2010). The results obtained for both hydrocarbons could be compared more accurately by using the same experimental methodology.…”

“…We estimated the amounts of seven aliphatic hydrocarbons absorbed by a driver (Yoshida, 2010), which were selected as the main compounds contributing to air pollution in automotive cabins on the basis of the results of our earlier studies (Yoshida and Matsunaga, 2006;Yoshida et al, 2006a, b). The estimation was conducted by examining the inhalation toxicokinetics of these compounds in rats.…”