Occupational Lead Exposure and Associations with Selected Cancers

The Shanghai Men's and Women's Health Study Cohorts
Background: Epidemiologic studies of occupational lead exposure have suggested increased risks of cancers of the stomach, lung, kidney, brain, and meninges; however, the totality of the evidence is inconsistent.
Objective: We investigated the relationship between occupational lead exposure and cancer incidence of these five sites in two prospective cohorts in Shanghai, China.
Methods: Annual job/industry-specific estimates of lead fume and lead dust exposure, derived from a statistical model combining expert lead intensity ratings with inspection measurements, were applied to the lifetime work histories of participants from the Shanghai Women's Health Study (SWHS; n=73,363) and the Shanghai Men's Health Study (SMHS; n=61,379) to estimate cumulative exposure to lead fume and lead dust. These metrics were then combined into an overall occupational lead exposure variable. Cohort-specific relative hazard rate ratios (RRs) and 95% confidence intervals (CI) comparing exposed to unexposed participants were estimated using Cox proportional hazards regression and combined by meta-analysis.
Results: The proportion of SWHS and SMHS participants with estimated occupational lead exposure was 8.9% and 6.9%, respectively. Lead exposure was positively associated with meningioma risk in women only (n= 38 unexposed and 9 exposed cases, RR = 2.4; 95% CI: 1.1, 5.0), particularly with above-median cumulative exposure (RR = 3.1; 95% CI: 1.3, 7.4). However, all 12 meningioma cases among men were classified as unexposed to lead. We also observed non-significant associations with lead exposure for cancers of the kidney (n= 157 unexposed and 17 ever exposed cases; RR = 1.4; 95% CI: 0.9, 2.3) and brain (n= 67 unexposed and 10 ever exposed cases; RR = 1.8; 95% CI: 0.7, 4.8) overall.
Conclusions: Our findings, though limited by small numbers of cases, suggest that lead is associated with risk of several cancers in women and men.

Source: Liao LM, Friesen MC, Xiang Y-B, Cai H, Koh D-H, Ji B-T, Yang G, Li H-L, Locke SJ, Rothman N, Zheng W, Gao Y-T, Shu X-O, Purdue MP. Environ Health Perspect, 2015.

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