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On-Road Sampling of Diesel Engine Emissions of Polychlorinated Dibenzo-p-Dioxin and Polychlorinated Dibenzofuran

The first known program to sample mobile heavy duty diesel engine emissions for polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran (“PCDD/F”) during highway and in-city driving routes was conducted. The post-muffler stacks of two diesel tractors hauling loaded trailers were sampled with a modified EPA Method 23 train. Extensive care was taken to ensure high data quality including sampling large volumes, repeat measurements, and high resolution mass spectroscopy. Analytical results from five tests showed significant yields of PCDD/F. The average emission factor obtained from this work was 0.029 nanograms (ng) international toxic equivalency (I-TEQ)/km. The upper limit of the 95% confidence interval provides an estimated emission factor of 0.106 ng I-TEQ/km. Based on these values and 1993 diesel truck travel estimates, the projected U.S. annual emissions from on-road diesel vehicles are 4.4 g I-TEQ/yr with a 95% confidence upper bound of 16.1 g I-TEQ/yr.