Occupational exposures to polycyclic aromatic hydrocarbons and respiratory and urinary tract cancers: An updated systematic review and a meta-analysis to 2014

Exposure to polycyclic aromatic hydrocarbons (PAHs) has been associated with an excess risk of respiratory tract and bladder cancers in several industries, but the issue requires further quantification. We updated a previous systematic review by reviewing in details cohort studies on workers employed in selected industries with potential PAH exposure published between 2006 and 2014, and we summarized through a meta-analytic approach the main results of all available cohort studies published between 1958 and 2014 investigating cancers of the respiratory and urinary tracts. Thirteen papers on cohort studies investigating cancer risk in workers exposed to PAHs were retrieved through the literature search. These included workers from aluminum production industries (seven studies), iron and steel foundries (two studies), asphalt workers (two studies), and carbon black production (two studies). In the meta-analysis, an excess risk of respiratory tract cancers (mainly lung cancer) was found in iron and steel foundries [pooled relative risk (RR) 1.31, 95 % confidence interval (CI) 1.08-1.59 from 14 studies], while a weak excess risk (pooled RR 1.08, 95 % CI 0.95-1.23 from 11 studies) emerged for aluminum production. A borderline increase risk was also observed for cancer of the bladder in the aluminum production (pooled RR 1.28, 95 % CI 0.98-1.68 from 10 studies) and in iron and steel foundries (pooled RR 1.38, 95 % CI 1.00-1.91 from 9 studies). This updated review and meta-analysis confirm the increased risk from respiratory tract and bladder cancers in selected PAH-related occupations. It cannot be ruled out whether such excesses are due, at least in part, to possible bias or residual confounding.