Lung cancer incidence among workers biologically monitored for occupational exposure to lead: a cohort study

Objective Earlier studies have reported increased risks of lung, kidney and brain cancers for exposure to lead. The International Agency for Research on Cancer (IARC) Working Group evaluated inorganic lead and its compounds probably carcinogenic to humans. This study aimed to assess the association between blood lead level in occupational exposure and risk of lung cancer. Methods The study was based on the follow-up of lung cancer incidence during 1973-2014 among 20 729 employees biologically monitored for their occupational lead exposure in 1973-1983. Duration of employment in the monitored work was assessed using records from the Finnish Centre for Pensions; and potential confounding by other occupational carcinogens using longitudinal information on the occupation in censuses and the Finnish National Job-Exposure Matrix (FINJEM). Occupation- and gender-specific prevalence of regular tobacco smoking and the socioeconomic status were also utilized in the adjustments for potential confounding. Results Positive trends were found for the elevated blood lead levels on the lung cancer risk. Among employees with the duration of employment of >= 60 months, the relative risk (RR) of lung cancer was 1.72 [95% confidence interval (CI) 1.28-2.31] for mean blood lead 1.0-1.9 mu mol/L and RR 2.63 (95% CI 1.71-4.05) for mean blood lead >= 2.0 mu mol/L, compared with mean lead <0.5 mu mol/L. The studied potential confounders did not explain the findings on the increased risk for lead exposure. Conclusions The current study lends support to the findings that exposure to lead increases lung cancer risk. Increased risks were seen already at rather low blood lead levels.