Cancer Risk Associated With Exposure to Bitumen and Bitumen Fumes: An Updated Systematic Review and Meta-Analysis

Objective:To evaluate whether cancer risks are increased among bitumen (asphalt) workers.Methods:Systematic review and meta-analysis of cancer risks (lung, upper aerodigestive tract (UADT), esophagus, bladder, kidney, stomach, and skin) and bitumen exposure. Certainty in the epidemiological evidence that bitumen-exposed workers experience increased cancer risks was rated using Grading of Recommendations Assessment, Development and Evaluation criteria.Results:After excluding lower-quality studies, lung cancer risks were not increased among bitumen-exposed workers (meta-relative risk [RR] 0.94, 95% CI 0.74 to 1.20, eight studies). Increased risks of UADT and stomach cancers were observed (meta-RR 1.31, 95% CI 1.03 to 1.67, 10 studies and meta-RR 1.29, 95% CI 1.03 to 1.62, seven studies, respectively).Conclusions:Except for lung cancer, evidence for increased cancer risks among bitumen-exposed workers was judged to be of low certainty, due to inadequate exposure characterization and unmeasured confounders (coal tar exposure, smoking, and alcohol consumption).