We expanded upon a previous pooled case-control analysis on diesel engine exhaust and lung cancer by including 3 additional studies and quantitative exposure assessment to evaluate lung cancer and subtype risks associated with occupational exposure to diesel exhaust, characterized by elemental carbon (EC) concentrations.
We used a quantitative EC job-exposure matrix for exposure assessment. Unconditional logistic regression models were used to calculate lung cancer odds ratios (ORs) and 95% confidence intervals (CI) associated with various metrics of EC exposure. Lung cancer excess lifetime risks (ELR) were calculated using life-tables accounting for all-cause mortality. Additional stratified analyses by smoking history and lung cancer subtypes were performed in men.
Our study included 16,901 cases and 20,965 controls. In men, exposure-response between EC and lung cancer was observed: ORs ranged from 1.09 (95% CI 1.00, 1.18) to 1.41 (95% CI 1.30, 1.52) for the lowest and highest cumulative exposure groups, respectively. EC-exposed men had elevated risks in all lung cancer subtypes investigated; associations were strongest for squamous and small cell carcinomas and weaker for adenocarcinoma. EC-lung cancer exposure-response was observed in men regardless of smoking history, including among never smokers. ELR associated with 45 years of EC exposure at 50, 20, and 1 μg/m3 were 3.0%, 0.99%, and, 0.04%, respectively, for both sexes combined.
We observed a consistent exposure-response relationship between EC exposure and lung cancer in men. Reduction of workplace EC levels to background environmental levels will further reduce lung cancer ELR in exposed workers.