Panko JM, Benson SM, Kreider ML. Meta-analysis of lung cancer risk related to diesel exposure by occupation and evaluation of exposure response. Abstract #2976. Poster at Society of Toxicology Annual Meeting, New Orleans,LA, March 13–17, 2016.
In 2012, the International Agency for Research on Cancer (IARC) changed the designation of diesel exhaust from a probable to causal lung carcinogen. Their decision was based on a qualitative assessment of many cohorts that had diesel exposure but also could have had ex-posure to other lung carcinogens. They did not attempt to account for any potential co-exposures nor did they evaluate whether there was a dose response relationship for diesel exposure and cancer risk. Our objective was to conduct meta-analyses for three occupational cohorts that are often overlooked in the evaluation of diesel exhaust exposure and the risk of lung cancer: dock workers, heavy equipment operators, and diesel engine mechanics. In all, 17 peer-reviewed manuscripts (n = 7 for dockworkers, n = 8 for heavy equipment operators, and n = 9 for mechanics) met our inclusion criteria and specifically identified diesel exhaust as the exposure of interest. Pooled effect estimates (meta-RR) and their corresponding 95% confidence intervals (CI) were calculated for each occupational group using the DerSimonian and Laird random effects model. Heavy equipment operators (meta-RR = 1.38; 95% CI: 1.00, 1.89) and dock workers (meta-RR = 1.34; 1.07, 1.68) had compa-rable risks of lung cancer, but mechanics were not at an increased risk (meta-RR = 1.15; 95% CI: 0.93, 1.44). Using exposure estimates reported in the IARC monograph we calculated the median elemental carbon exposures from diesel emissions for dock workers (7 μg/m^3), diesel en-gine mechanics (20 μg/m^3), and heavy equipment operators (47.5 μg/m^3). In short, the diesel exposure estimates do not correspond to the risk estimates, which suggests the lack of a dose-response relationship. The increased risks observed could be related to exposures to other car-cinogens or other confounding factors. Hence, a finding of “risk” for any given diesel cohort may not necessarily mean the risk was related to diesel exhaust.