Concentrations of 1,3-butadiene and benzene have been measured inside the cabins of both pre-1986 (non-catalyst-equipped) and post-1986 (catalyst-equipped) vehicles on freeway and urban driving routes around Sydney, Australia. Mean in-vehicle concentrations of 1,3-butadiene and benzene observed for the newer cars during the morning peak-hour were 5.5 +/- 2.1 and 22.1 +/- 4.1 ppb respectively. Corresponding values for the older, poorly maintained vehicle were 11.5 +/- 3.0 and 48.1 +/- 6.9 ppb, respectively, about double those of newer vehicles. I,3-Butadiene was only observed at significant concentrations inside the cabins of moving vehicles during peak-hour traffic. Concentrations of this species both in the ambient air, and in the vehicle cabins during freeway trips in non-peak periods, were near or below the detection limit of 0.1 ppb. Therefore, commuter trips are likely to be the major source of exposure to this compound. Both using the airconditioner and driving with the vents closed were the most effective ventilation conditions for minimising the exposure to fresh exhaust. For both conditions, trip average in-vehicle concentrations were about 70% of those in the air directly outside the vehicle. For vehicles left in a parking station during the day, exposures to 1,3-butadiene during evening commuter trips were observed to be about 1.2 times those in the morning peak-hour. Concentrations of volatile organic compounds measured inside buses were about 50% of those observed for newer cars. (C) 1997 Elsevier Science Ltd.
