Benzene exposures caused by traffic in Munich public transportation systems between 1993 and 1997

Volatile aromatics benzene, toluene, xylenes, the BTX-aromatics. were measured between 1993 and 1997 in buses and trams in Munich center and along main roads during regular rides. The sampling time was between 07.00 and 00.00 h. A total of 631 probes were sampled and centrally analyzed. In the mean of 5 years we found 15.0 mg benzenerm3, 50% above the limit of the 23. BImSchV and 107.5 mg BTX aromatesrm3 along the strongly traffic loaded main streets. Splitting up these mean emissions into single years we observed a trend toward a decline of mean immissions of all volatile aromatics benzene from 23.8 mgrm3 to 7.4 mgrm3. and the sum of BTX aromatics from 147.5 mgrm3 to 59.4 mgrm3.. The measured hydrocarbon concentrations in Munich center were consistent with the long range theoretical calculations concerning the decrease of traffic-caused benzene immissions in cities. If the current trends continue, we can expect benzene concentrations to be below 5 mgrm3 by the year 2001 and below 2.5 mgrm3 by the year 2008. At these levels, the carcinogenic risk from benzene is probably less significant than the risks to public health from other car exhaust components.