[Exposure of the population to volatile organic compounds inside an automobile and a subway train]

Air quality, in particular in urban regions, is affected by the emissions of the traffic and meanwhile for some substances motor vehicles became the dominating source. For valid quantitative risk assessment of the general population it is necessary to have informations about the main routes of exposure. Therefore in a pilot study 1994 and two times in summer 1995 and winter 1996 aromatic hydrocarbons, carbon monoxide (CO) and carbon dioxide (CO2) were determined under different meteorologic conditions inside of a car (a two year old VW-Golf with a three-way catalyst) and in a subway-train. The car route followed the subway (31 km underground) and crossed the central parts of Berlin in streets with high traffic density. The mean values for benzene obtained during the three measurement periods inside the car were 21.1/21.5 and 21.6 micrograms/m3 (daily maximum: 31.9/26.3 and 35.0 micrograms/m3) and inside the subway 8.4/5.4 and 7.4 micrograms/m3 (daily maximum: 16.0/7.4 and 10.3 micrograms/m3). The mean levels of CO in the car were 6 ppm (summer) and 5 ppm (winter) respectively, with peak concentrations of 33 and 70 ppm (10-minutes maximum). In the subway the values were 2 ppm (summer and winter); (10-minutes maximum: 5 and 12 ppm). A comparison between the two types of traffic shows three times higher concentrations of benzene inside the car. Our results demonstrate that the exposure of car occupants to benzene has to be taken into account for risk assessment. The concentration of CO inside the car is three to four times higher than in the subway train. Compared with other studies we found only low concentrations of CO inside the car.