Roadside and in-vehicle concentrations of monoaromatic hydrocarbons

Airborne concentrations of benzene, toluene and the xylenes have been measu red inside passenger cars whilst driven along major roads in the city of Bi rmingham, UK, as well as immediately outside the car, and at the roadside. A comparison of concentrations measured in the car with those determined fr om immediately outside showed little difference, with a mean ratio for benz ene of 1.17 +/- 0.34 and for toluene 1.11 +/- 0.16 (n = 53). The ratio of i n-car to roadside concentration was rather higher at 1.55 +/- 0.68 for benz ene and 1.54 +/- 0.72 for toluene (n = 53). The roadside concentrations wer e typically several-fold higher than those measured at a background suburba n monitoring station within Birmingham, although much variation was seen be tween congested and uncongested roads, with concentrations adjacent to unco ngested roads similar to those measured at the background monitoring statio n. Measurements of benzene and toluene in a car driven on a rural road outs ide the city showed very comparable in-car and out-of-car concentrations st rengthening the conclusion that pollution inside the car is derived from po llutants outside entering with ventilation air. The exceptions were an olde r car where in-car concentrations appreciably exceeded those outside (in-to out-vehicle ratio = 2.3 for benzene and 2.2 for toluene where n = 5) indic ating probable self-contamination, and a very new car which built up increa sed VOC concentrations when stationary without ventilation (in-to out-vehic le ratio = 2.4 for benzene and 3.3 for toluene where n = 5). A further set of measurements inside London taxi cabs showed concentrations to be influen ced by the area within which the taxi was driven, the traffic density and t he presence of passengers smoking cigarettes. (C) 1998 Elsevier Science Ltd . All rights reserved.