PCDD/F Emissions from heavy duty vehicle diesel engines

The currently available information on PCDD/F emissions from diesel vehicles is briefly surveyed. Considerable uncertainty is identified concerning the emissions from heavy duty diesel trucks which have been measured only twice so far. These measurements led to emission factors differing by a factor of 200; similar discrepancy was also revealed by measurements of ambient air in traffic tunnels. New PCDD/F emission measurement results are presented which have been carried out at the exhaust systems of a stationary engine and of a modern heavy duty vehicle engine at transient operation conditions simulated on a test bench. PCDD/F concentrations in the exhaust gases were found to be in the range of control blank samples. Based on the highest concentration observed in the truck engine exhaust (9.7 pg I-TEQ/dry standard m3) a worst case estimate of the annual PCDD/F emission freight from diesel fuel combustion in the European countries of about 30 g I-TEQ/year is calculated. This emission appears to be irrelevant compared to the overall emission rate of more than 6,000 g I-TEQ/year being inventoried recently. Finally the possibilities to link congener/homologue profiles of diesel emission to profiles found in food or human samples are discussed.