PCDD/F emissions from heavy duty vehicle diesel engines

The currently available information on PCDD/F emissions from diesel vehicle s is briefly surveyed. Considerable uncertainty is identified concerning th e emissions from heavy duty diesel trucks which have been measured only twi ce so far. These measurements led to emission factors differing by a factor of 200; similar discrepancy was also revealed by measurements of ambient a ir in traffic tunnels. New PCDD/F emission measurement results are presente d which have been carried out at the exhaust systems of a stationary engine and of a modern heavy duty vehicle engine at transient operation condition s simulated on a test bench. PCDD/F concentrations in the exhaust gases wer e found to be in the range of control blank samples. Based on the highest c oncentration observed in the truck engine exhaust (9.7 pg I-TEQ/dry standar d m(3)) a worst case estimate of the annual PCDD/F emission freight from di esel 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. F inally the possibilities to link congener/homologue profiles of diesel emis sion to profiles found in food or human samples are discussed. (C) 1999 Els evier Science Ltd. All rights reserved.