In March of this year (here), we reported that the Health and Safety Executive (HSE) Workplace Health Expert Committee had reacted to an International Agency for Research on Cancer (IARC) Monograph, which concluded that exposure to mild steel welding fumes is associated with elevated risk of lung cancer and kidney cancer in humans.
Welding involves heating materials, often metallic in nature, to sculpt and join. When vaporised (gaseous) metals are cooled in the air, the condensation reaction creates very fine solid particles that constitute potentially damaging welding fumes.
The exact composition of these fumes can depend upon the type of metals involved, the type of welding process, and the type of occupational setting where the welding is performed. For example, stainless steel usually produces fumes that contain high concentrations of nickel compounds and chromium, whereas other types of steel often produce fumes that contain high concentrations of fine particulate matter, such as soot, dust and chemicals.
As a result of the 2017 Monograph findings, the 1989 classification of welding fumes as ‘possibly carcinogenic to humans’ (Group 2B) was upgraded to ‘carcinogenic to humans’ (Group 1).
Effective from February 2019, the HSE followed suit by reclassifying welding fumes (including mild steel welding fumes) as a human carcinogen, triggering an immediate change in enforcement expectations in affected industries, such as:
- Plant maintenance; and
- Hydraulic fracturing, or fracking.
It is estimated that there are around 110 million workers exposed to welding fumes worldwide. Was this a well-timed decision?
Incidentally, the HSE reclassification has coincided with a new study, published in the Occupational & Environmental Medicine journal, on the link between exposure to welding fumes and lung cancer.[i]
This was a meta-analysis of case-control and cohort studies, whereby the University of Utah researchers investigated 17 million participants from 45 previously published studies.
Results showed that exposed workers (‘ever’ exposed) had a 52.5% higher lung cancer rate (weighted average) than non-exposed (‘never’ exposed) workers and when the researchers considered the effects of contributing risk factors, including cigarette smoke and asbestos, there was still a 17% greater risk of developing lung cancer among exposed workers.
The study authors established that:
‘[The] results support the conclusion that exposure to welding fumes increases the risk of lung cancer, regardless of the type of steel welded, the welding method (arc vs gas welding) and independent of exposure to asbestos or tobacco smoking’.
Although it was evaluated that ‘shipyard welders’, ‘mild steel welders’ and ‘stainless steel welders’ had a 32%, 44% and 38% higher risk of lung cancer onset than non-exposed workers, respectively, the study was limited by its inability to ascertain how cancer risk varied between ‘flux-core arc’, ‘gas metal arc’, and ‘gas tungsten arc’ welding processes.
Naturally, the study was also limited by the strength of the pool of data available for review. In this instance, the researchers could not assess how lung cancer risk changed with increasing duration of welding exposure.
The meta-analysis did not go on to explain whether, or how, welding fumes directly cause lung cancer. To do so would have exceeded its initial purpose.
When prompted for comment, Paul Cullinan, an Occupational and Environmental Health Researcher at Royal Brompton Hospital and Imperial College London, who was not involved with the meta-analysis, told Reuters:
‘The process can take decades of exposure. Workers and their employers need to continue to contain welding fume so that it isn’t inhaled in large quantities. The best way to do this is through the use of local “exhaust” ventilation which carries the fume away from the worker’s breathing zone. Second best is the use of protective masks’.[ii]
Despite the fact that research on welding fume carcinogenicity is still relatively young, this latest study would appear to support the HSE decision to respect the 2017 IARC Monograph.
[i] Honaryar MK, Lunn RM, Luce D, et al Welding fumes and lung cancer: a meta-analysis of case-control and cohort studies Occupational and Environmental Medicine 2019;76:422-431 <https://oem.bmj.com/content/76/6/422> accessed 23 May 2019.
[ii] Lisa Rapaport, ‘More evidence welding fumes raise lung cancer risk’ (21 May 2019 Reuters) <https://uk.reuters.com/article/us-health-welding-cancer/more-evidence-welding-fumes-raise-lung-cancer-risk-idUKKCN1SR2IA> accessed 22 May 2019.