Exposure to welding fumes increases lung cancer risk among light smokers but not among heavy smokers: evidence from two case–control studies in Montreal

Abstract

We investigated relationships between occupational exposure to gas and arc welding fumes and the risk of lung cancer among workers exposed to these agents throughout the spectrum of industries. Two population-based case–control studies were conducted in Montreal. Study I (1979–1986) included 857 cases and 1066 controls, and Study II (1996–2001) comprised 736 cases and 894 controls. Detailed job histories were obtained by interview and evaluated by an expert team of chemist–hygienists to estimate degree of exposure to approximately 300 substances for each job. Gas and arc welding fumes were among the agents evaluated. We estimated odds ratios (ORs) and 95% confidence intervals (CIs) of lung cancer using logistic regression, adjusting for smoking history and other covariates. The two studies provided similar results, so a pooled analysis was conducted. Among all subjects, no significant association was found between lung cancer and gas welding fumes (OR = 1.1; 95% CI = 0.9–1.4) or arc welding fumes (OR = 1.0; 95% CI = 0.8–1.2). However, when restricting attention to light smokers, there was an increased risk of lung cancer in relation to gas welding fumes (OR = 2.9; 95% CI = 1.7–4.8) and arc welding fumes (OR = 2.3; 95% CI = 1.3–3.8), with even higher OR estimates among workers with the highest cumulative exposures. In conclusion, there was no detectable excess risk of lung cancer due to welding fumes among moderate to heavy smokers; but among light smokers we found an excess risk related to both types of welding fumes.

Risk of lung cancer associated with six types of chlorinated solvents: results from two case–control studies in Montreal, Canada: Table 1

“…Previous reports from our group have discussed a number of strengths of our studies (including relatively high sample size, high participation rates, histological confirmation of diagnoses, intensive expert-based exposure assessment blinded to case/control status, and good control of potential confounding by smoking, socio-economic/demographic variables and other occupational carcinogens) as well as a number of limitations including limited statistical power, multiple inference in a ‘hypothesis-generating’ paradigm, a high proportion of proxy responses, and exposure assessment not based on local measurements and thus subject to error 24 25. We will not repeat those discussions here; suffice it to say that these results represent a valuable contribution to the evidence regarding the lung carcinogenicity of chlorinated solvents, but require caution in the interpretation of both null and ‘positive’ results.…”

Welding Fumes, a Risk Factor for Lung Diseases

“…A case-control study performed in Montreal showed a significant increase of risk for lung cancer both in gas (OR = 2.9) and arc (OR = 2.3) WFs in non/low smokers but not in moderate/heavy smokers. The authors concluded that results in heavy smokers might be due to the strong effect of tobacco smoking, which could mask the weak effect of WFs on lung cancer [158]. A recent prospective study revealed a positive relation between duration of exposure in years and lung cancer risk among heavy smokers.…”

Oxidative stress, telomere shortening, and DNA methylation in relation to low‐to‐moderate occupational exposure to welding fumes

“…Approximately 16,000 workers in Sweden are welders by occupation, and several million people worldwide are occupationally exposed to welding fumes [Antonini, ; IVL Svenska Miljöinstitutet]. Welding fumes have been categorized as a possible human carcinogen (Group 2B) [IARC, ], and studies show a 25%–40% increase in risk (measured as odds ratio) for lung cancer in welders [Hansen et al, ; Ambroise et al, ; 't Mannetje et al, ; Vallieres et al, ; Kendzia et al, ]. However, negative results have also been reported in large cohorts from Sweden and other countries [Sjögren et al, ; Danielsen et al, ; Gustavsson et al, ].…”