Ultraviolet radiation from welding and possible risk of skin and ocular malignancy

The overwhelming majority of skin cancers are caused by exposure to ultraviolet radiation (UVR) from the sun. However, it is possible that non-solar sources of UVR (such as arc welding) may also cause cancer. The purpose of this review is to explore the evidence that radiation from arc welding may significantly increase the risk of skin or ocular malignancy in welders, those working near them, or occasional users of arc welding processes, such as mechanics, sculptors and farmers.

Ultraviolet radiation and cancer

The full spectrum of UVR can be classified into three groups, based on wavelength: ultraviolet A (UVA) (400–315 nm), ultraviolet B (UVB) (315–280 nm) and ultraviolet C (UVC) (280–100 nm).

Over 98% of solar UVR exposure is in the form of UVA. It penetrates the skin more deeply than UVB or UVC, but is less associated with DNA damage. This may mean that UVA is least likely to produce skin malignancies.

UVB accounts for less than 2% of our solar UVR exposure, as much of it is absorbed in the upper atmosphere. UVB is responsible for most of the DNA damage within skin cells, and arguably most of the resultant skin cancers.

UVC exposure is insignificant for most people, as solar UVC is readily absorbed in the atmosphere before reaching the earth’s surface. Knowledge of the effects of UVC on skin is less clear, but it may be as dangerous to skin as UVB.

Arc welding produces the full spectrum of UVR. The short distance between the arc and the welder’s skin may not be sufficient to absorb most of the UVB and UVC. Arc welders may therefore be at significantly increased risk of developing actinic skin and ocular damage, including malignancy, particularly if they have inadequate protection. Furthermore, thermal burns from hot metal can occur when welding and contribute to this risk.

Review of the evidence

A literature search was conducted in December 2003 using the PubMed (www. ncbi.nlm.nih.gov/PubMed) and Blackwell Synergy (www. blackwell-synergy.com/servlet/useragent?func=showHome) electronic databases. The key search terms used were basal cell carcinoma, squamous cell carcinoma, skin cancer, melanoma, weld, welding, arc, radiation and ultraviolet. We searched for all relevant material over the past 30 years.

Of the five articles we found that commented on cases of skin cancer possibly attributable to welding, only one was a case–control study of the risk of skin cancer from arc welding. This study, by Emmett et al, observed that welders often had skin erythema and small scars from burns, but did not find a link between welding and the development of skin cancer. Several features of the study are noteworthy. The researchers studied only one workplace, which was described as having “well run welding operations which use and enforce current safety standards”. The welders “predominantly welded mild steel”. Their average age was relatively young (43 years), and they had been working for the same employer for an average of 16.9 years. As skin cancer often occurs decades after the significant UVR exposure, it is conceivable that the UVR skin damage experienced by workers in the study by Emmett et al had not yet manifested as malignancy. Furthermore, the study did not include examination for naevi. At the time, the relationship between atypical naevi and melanoma was not understood. We now recognise that multiple atypical naevi are associated with a significantly greater risk of developing melanoma.