AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Diesel Exhaust Exposure and Lung Cancer: A Case Study in Data Access, Exposure Assessment, and Extended Analyses
Kenny Crump, Cynthia Van Landingham, ROGER MCCLELLAN, Private Consultant
Abstract Number: 560 Working Group: Health Related Aerosols
Abstract The International Agency for Research on Cancer (IARC) in 2012 classified diesel exhaust exposure as a "human carcinogen" largely based on findings from the Diesel Exhaust in Miners Study (DEMS). This action raises the question - Are results of analysis of the DEMS data sufficiently robust to support Quantitative Risk Assessment? DEMS was designed to test for an association between exposure to Diesel Engine Exhaust (DEE) and lung cancer in workers in 8 nonmetal mines from dieselization through 1997. Respirable Elemental Carbon (REC) was used as a metric for DEE and estimated from diesel equipment Horse Power (HP), earlier measurements of CO in the mines and assumed relationships among HP, CO, and REC. Cox proportional hazard models revealed a statistically significant association between REC and lung cancer in the total cohort and ever underground workers. Statistically significant associations were also observed in a nested case - control study controlling for smoking. The authors of this abstract gained access to DEMS data and extended the original analyses. Uncertainties in the REC estimates using CO as a surrogate for REC prompted us to develop alternative REC estimates using only HP and CFM. The alternative REC exposure estimates were applied in a conditional logistic regression of the case-control data. Trend slopes calculated with new REC estimates were not statistically significant. Slopes were smaller by a factor of 5 without control and factors of 12 with control for radon exposure compared to slopes in original analyses. A consistent lung cancer effect was not observed in always underground miners, a sub-group not originally analyzed. The varied results from different analyses should be considered in conducting quantitative risk assessments using DEMS data. This study illustrates the value of data sharing, construction of alternative exposure estimates and conduct of alternative analyses.