Commuter exposure to volatile organic compounds under different driving conditions

The driving conditions that were tested for the in-vehicle concentrations o f selected volatile organic compounds (VOCs) included transport modes, fuel distributions, vehicle ventilation conditions, driving routes, commute sea sons, car models, and driving periods. This study involved two sampling sea sons (winter and summer). The in-auto/in-bus/fixed site ratio of the winter time mean concentrations was about 6/3/1 for total VOCs and 8/3/1 for benze ne. On the median, the in-auto/in-bus exposure ratio ranged from 1.5 to 2.8 for the morning commutes, and ranged from 2.4 to 4.5 for evening commutes, depending on the target compounds. The wintertime in-auto concentrations w ere significantly higher (p < 0.05), on the average 3-5 times higher, in a carbureted engine than in the three electronic fuel-injected cars. For the summertime in-auto concentrations of the target compounds except benzene, t here were no significant differences between low and high ventilation condi tions on the two urban routes. The urban in-auto benzene concentration was significantly higher (p < 0.05) under the low ventilation condition. For th e rural commutes, the in-auto concentrations of all target compounds were s ignificantly higher (p < 0.05) under the low ventilation condition. The in- auto VOC concentrations on the two urban routes did not differ significantl y, and they were greater than the rural in-auto concentrations, with the di fferences being significant (p < 0.05) for all target compounds. The summer time in-auto concentrations of benzene and toluene were greater than the wi ntertime in-auto concentrations, with the difference being significant(p < 0.05), while the concentrations of the other target compounds were not sign ificantly different between the two seasons. Neither car models nor driving periods influenced the in-auto VOC concentrations. (C) 1998 Elsevier Scien ce Ltd. All rights reserved.