This issue of JOEH has been curated to focus on the current state of knowledge regarding welding fume exposure and health outcomes. In October 2017, the Synergist published an early announcement about the IARC Working Group’s assessment of the cancer risk of welding fumes.[Citation1] This announcement informed the industrial hygiene community about the upcoming reclassification of welding fumes as a known carcinogen (Group 1), an update from the 1990 determination of its possible carcinogen status (Group 2B).[Citation2] In September 2018, the IARC released a monograph that included the official determination that welding fumes are a Group 1 carcinogen.[Citation3] Both case-control and cohort studies consistently identified a positive association between lung cancer and working as a welder across country, occupational settings, and time. A limitation of the data is that welding fume exposures were seldom measured in these studies, and the exposures were assigned through indicators (job titles, industry sector, welding processes) or by expert assessment or self-report by study participants.
While exposure data were limited in many studies, the increased risk of lung cancer was observed with increased duration of employment. The IARC Working Group concluded that the increased risk of lung cancer for welders was observed regardless of the material or welding method used. It is important to note that welding fumes, even without the presence of known carcinogens (chromium VI, nickel), are included in this Group 1 designation.
From a mechanistic perspective, the IARC evaluated whether welding fumes met the required qualifying characteristics to be a carcinogen. The Working Group reported there was strong evidence of chronic inflammation and immunosuppression. There was moderate evidence that welding fumes are genotoxic, induce oxidative stress and alter cell proliferation and cell death, but weak evidence that they modulate receptor-mediated effects (limited studies). Many of these characteristics were demonstrated in exposures to both stainless steel (with known carcinogenic metal components) and mild steel (without these carcinogenic metals).
Other cancer outcomes were assessed by IARC. Positive associations between welding and kidney cancer were found, but bias and confounding by exposures to solvents could not be ruled out. Other cancers had limited data (leukemia, non-Hodgkin’s lymphoma, head/neck cancers) or inconsistent findings (brain cancers, bladder cancers). The IARC Working Group did identify sufficient evidence regarding the postulate that UV radiation from welding causes ocular melanoma, showing increased rates for welders experiencing eye burns, a proxy for UV exposure. The ultraviolet light from welding is also now classified as a known human carcinogen, with a Group 1 designation.
In advance of the monograph’s release, the question of what the industrial hygiene and exposure assessment communities need to do with this information was posed by professionals at the 2018 American Industrial Hygiene Conference & Exposition (AIHce). Employers should include this cancer designation in hazard communication to welders, but the issue of workers’ exposures and whether exposures to iron (from mild steel) play a role in the development of cancer needs discussion. In November 2018, JOEH sent out requests for manuscripts on the topic of welding fume exposure and health outcomes for this June issue, referencing the new IARC monograph. All articles in this special issue have been peer reviewed using the standard double-blind review process used by JOEH.
The goal of this issue is to ensure that the profession understands the current state of knowledge regarding welding fume exposure and health outcomes, including where we still have questions. Technical articles in this issue provide information on exposure characterization for welding (and other metal) exposures. Two commentaries on the IARC monograph are also included in this issue. The first examines whether this finding should change how we assess exposures to welding fumes, and the second summarizes the state of knowledge of tumor formation from welding fumes. These commentaries provide suggested future directions that we hope sparks additional discussion and research that will improve our understanding of the risks of welding fume exposures and necessary precautions to protect welders.
Editor-in-Chief, JOEH
Reference
- Mirer F.: Risky Business: Ironing Out Welding Carcinogenicity? Synergist, Oct:10–11, 2017.
- International Agency for Research on Cancer: Chromium, nickel, and welding. In IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, World Health Organization (ed.). Geneva, 1990, pp. 447–525.
- International Agency for Research on Cancer: Welding, Molybdenum Trioxide, and Indium Tin Oxide. In IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Volume 118, World Health Organization (ed.). Lyon, France, 2018, pp. 36–265. Available at http://publications.iarc.fr/569.