Emissions of benzene, toluene, xylenes and 1,3-butadiene from a representative portion of the Australian car fleet

The exhaust emissions of the air toxics benzene, toluene, total xylenes and 1,3-butadiene have been measured in the cold transient (CT), cold stabilised (CS) and hot transient (HT) phases of the Australian Design Rule (ADR) 37/00 Drive cycle for 19 pre-1986 non-catalyst-equipped vehicles fuelled with leaded petrol, and 56 post-1985 catalyst-equipped vehicles fuelled with unleaded petrol. Per vehicle exhaust emissions, averaged over the 3 phases of the ADR 37/00 test, of 1,3-butadiene, benzene, toluene, and total xylenes for the older vehicles were about 19, 139, 240 and 164 mg km ^-1 respectively. The corresponding emissions for the better 46 of the 56 post-1985 vehicles tested were 1.7, 28.1, 36.4, and 27.0 mg km ^-1 respectively. The remaining 10 high polluting post-1985 vehicles had emission rates comparable to those vehicles not equipped with catalytic converters, suggesting that about 20% of post-1985 vehicles have malfunctioning or poorly operating catalysts. For the non-catalyst-equipped, pre-1986 vehicles, CS and HT emissions were about 60% of the CT emissions. For the better 46 post-1985 vehicles, average emissions during the CS and HT phases were about 20-25%, 12-16%, 11-14%, and 7-13% of the CT emissions for benzene, toluene, the xylenes, and 1,3-butadiene, respectively. The emissions from a small number (9) of non-catalyst-equipped, pre-1986 vehicles were determined using unleaded and leaded petrol. The emissions of all four target compounds were found to be significantly lower when unleaded petrol was substituted for leaded petrol. The greatest percentage emission reductions were observed for the CT phase, ranging from 25% for 1,3-butadiene to 35% for toluene. Emissions averaged over the 3 phases were reduced by 10% for, 1,3-butadiene and by 16-18% for the aromatic compounds. Per vehicle total (heat build and hot soak) evaporative emissions of 1,3-butadiene, benzene, toluene and xylenes from pre-1985 vehicles during the Sealed Housing Evaporative Determination tests were 36, 646, 679 and 260 mg per test, respectively. Corresponding values for the post-1985 vehicles were much lower at 14, 76, 131 and 65 mg per test, respectively. Heat build evaporative emissions of the four air toxics from pre-1986 vehicles were greater than those from the newer vehicles by factors ranging from 2.8 for 1,3-butadiene to 16 for benzene. The corresponding values for hot soak emissions were 1.8 and 5.2 respectively.