Aromatic hydrocarbons in the atmospheric environment: Part I. Indoor versus outdoor sources, the influence of traffic

Six aromatic hydrocarbons (benzene, toluene, ethylbenzene and the three isomeric xylenes) were monitored in the indoor and outdoor air of 115 private non-smoker homes ( similar to 380 rooms), about half of which were located in two city streets in Hannover (Northern Germany) with high traffic density, the other half in rural areas with hardly any traffic at all. This environmental monitoring was complemented by human biomonitoring (i.e. the determination of aromatic hydrocarbons in blood and exhaled air). Particular attention was paid to benzene as a result of its carcinogenicity. In the city streets with high traffic density, an average benzene concentration of 3.1 mug m(-3) and in the rural areas of 1.8 mug m(-3) was found in these non-smoker homes tall data = geometric means), which reflects the influence of the traffic (automobile exhaust) on the benzene level found indoors. Source identification is also possible by determining the indoor/outdoor (I/O) concentration ratio. For the rooms facing the city street, this I/O ratio is close to 1 for all aromatic hydrocarbons studied with the exception of toluene (I/O = 3.5), while in the rural areas I/O ratios for the individual compounds ranging in 6-9 were determined, with the exception of benzene where the I/O ratio is only 1.5. These I/O ratios in the city street with high traffic density indicate that an equilibrium between indoor and outdoor air is almost reached. Indoor sources prevail only in the case of toluene. In contrast, in the rural area, indoor sources dominate for all aromatic hydrocarbons except benzene, the indoor level of which is mainly influenced by the outdoor air even in areas of very low traffic density. However, weak indoor sources must exist also for this compound even in non-smoker homes. The internal exposure of the non-smoking inhabitants of these homes to benzene is very low. Depending on the living area, mean values of 61-67 ngl(-1) benzene in blood and 0.9-1.2 mug m(-3) in the exhaled air were found. (C) 2001 Elsevier Science Ltd. All rights reserved.