Lung cancer risk among bricklayers in a pooled analysis of case-control studies

Abstract

Bricklayers may be exposed to several lung carcinogens, including crystalline silica and asbestos. Previous studies that analyzed lung cancer risk among these workers had several study design limitations. We examined lung cancer risk among bricklayers within SYNERGY, a large international pooled analysis of case-control studies on lung cancer and the joint effects of occupational carcinogens. For men ever employed as bricklayers we estimated odds ratios (OR) and 95% confidence intervals (CI) adjusted for study center, age, lifetime smoking history and employment in occupations with exposures to known or suspected lung carcinogens. Among 15,608 cases and 18,531 controls, there were 695 cases and 469 controls who had ever worked as bricklayers (OR: 1.47; 95% CI: 1.28-1.68). In studies using population controls the OR was 1.55 (95% CI: 1.32-1.81, 540/349 cases/controls), while it was 1.24 (95% CI: 0.93-1.64, 155/120 cases/controls) in hospital-based studies. There was a clear positive trend with length of employment (p < 0.001). The relative risk was higher for squamous (OR: 1.68, 95% CI: 1.42-1.98, 309 cases) and small cell carcinomas (OR: 1.78, 95% CI: 1.44-2.20, 140 cases), than for adenocarcinoma (OR: 1.17, 95% CI: 0.95-1.43, 150 cases) (p-homogeneity: 0.0007). ORs were still elevated after additional adjustment for education and in analyses using blue collar workers as referents. This study provided robust evidence of increased lung cancer risk in bricklayers. Although non-causal explanations cannot be completely ruled out, the association is plausible in view of the potential for exposure to several carcinogens, notably crystalline silica and to a lesser extent asbestos.

Keywords: bricklayers; case-control studies; epidemiology; lung neoplasms; occupational health.

Figure 1

Association between lung cancer risk and length of employment as bricklayers using restricted cubic splines (knots at 10th, 25th, 50th, 75th and 90th percentiles of length of employment, log-transformed), the SYNERGY study, 1985–2010. Note: A/B, occupations known (list A) or suspected (list B) to be associated with lung cancer; CI, confidence interval; OR, odds ratio. Vertical bars close to the horizontal axis indicate lung cancer cases.

Figure 2

Study-specific and overall meta-analytic odds ratios (OR) for bricklayers, the SYNERGY study, 1985–2010. Note: A/B, occupations known (list A) or suspected (list B) to be associated with lung cancer; CI, confidence interval; D+L, DerSimonian and Laird random effect estimate; I–V, inverse–variance fixed effect estimate.