Most skin cancers are caused by solar ultraviolet radiation (UVR) and it is believed that the most dangerous part of the UVR spectrum is Ultraviolet B (UVB) (315 – 280 nm). Fortunately, most of UVB is screened from the earth's surface by the outer atmosphere. Arc welding produces the full spectrum of UVR, including UVB. It is therefore likely that welders will be exposed to a greater risk of skin cancer than the rest of the population. Nevertheless, there has been minimal exploration to determine whether the UVR from arc welding is causing skin cancer.
The only major study of skin cancer from arc welding involved examining welders who were careful to protect themselves. The workers did not demonstrate an increased incidence of skin cancers in this study. Cancers may take years to develop and there was no follow-up of these workers to see if an increased incidence of cancers developed over time. Further, the radiation protection observed by these welders may not be typical of the welding industry as a whole. As such, the study cannot be extrapolated beyond this safe workplace and these young welders. Further studies are needed examining welders in their senior years, ensuring there is a lengthy time for their skin to have developed cutaneous malignancies. In contrast to cutaneous malignancies, there is evidence that welding increases the risk if ocular malignant melanoma. Just as we urge the public to protect themselves from UVR, we need to consider similar advice to arc welders
The overwhelming majority of skin cancers are caused by exposure to ultraviolet radiation (UVR) from the sun. However, there are non-solar sources of UVR that may also cause cancer. The purpose of this review is to explore the evidence that radiation from the welding arc may also be a significant risk to welding trades people, people near arc welding trades people and to occasional users of arc welding processes such as mechanics, sculptors and farmers.
A literature search was conducted using Pubmed and Synergy. The key words used in the search were: “basal cell carcinoma”, “squamous cell carcinoma”, “skin cancer”, “melanoma”, “weld”, “welding” “arc”, “radiation” and “ultraviolet”.
Ultraviolet Radiation and Cancer:
The full spectrum of UVR can be classified into three groups based on wavelength. Ultraviolet “A” (UVA) spans UVR with the longest wavelength (400 – 315 nm). Over 98% of solar UVR exposure is UVA. UVA penetrates the skin more deeply than Ultraviolet “B” (UVB) or Ultraviolet “C” (UVC), but is less associated with DNA damage and the formation of pyrimidine dimmers. 283 284
UVB includes UVR with shorter wavelengths (315 – 280 nm). UVB accounts for less than 2% of our solar UVR exposure because much of it is absorbed in the upper atmosphere. UVB accounts for most of the DNA damage within skin cells and most of the resultant skin cancers. 283 284
UVC covers the range of UVR with the shortest wavelength (280 – 100 nm). UVC exposure is insignificant for most people because solar UVC is readily absorbed in the atmosphere before the damaging radiation reaches the earth’s surface. Knowledge of the effects of UVC on skin is less clear. However, UVC may be as dangerous to skin as UVB. 284 285
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 be at significantly increased risk of developing actinic skin damage including malignant melanoma and non-melanoma skin cancer (NMSC), particularly if they have inadequate protection.
Apart from producing UVR, arc welding can also produce thermal burns on the skin of welders. Such burns may also contribute to skin developing skin cancer.286
Review of evidence
Table 2 summarizes the limited studies into the risk of skin cancer from arc welding. The only formal case control study was by Emmett and co-workers 287, who studied 77 welders, 75 other workers exposed to welding and 58 non-exposed workers. Emmett did not find a link between welding and the development of cancer on the skin of welders.
A number of features of the Emmett study are noteworthy. They studied one workplace, described by Emmett as “a plant where both management and workers were careful to maintain hygienic practices. . . well-run welding operations which use and enforce current safety standards. . .’ He also said that; ‘… it is not believed these results can be extrapolated to welding operations which do not employ good practices.”
The study looked at relatively young people. The average age of the workers examined was 45. The average age of welders was 43 and they had been working for the same employer for an average of 16.9 years. Skin cancer often occurs decades after the significant UVR exposure. It is conceivable that the UVR skin damage experienced by those workers had not manifested as actinic changes because they were relatively young.
The Emmett study involved workers welding predominantly with mild steel. Higher intensity welding such as welding aluminium was not explored. Formal medical histories of those examined were not available.
Furthermore, the Emmett study did not include examination for naevi. At the time the relationship between atypical naevi and malignant melanoma was not understood. We now recognize that multiple atypical naevi are associated with a significant increase in the subsequent incidence of malignant melanoma.288
The evidence linking ocular melanoma with welding is contradictory (Table 2). In an overview on the topic, Tenkate 289, 290 postulated that UVR from arc welding was one of the most intense artificial sources of optical radiation.
Effect of Welding Technique on UVR Exposure:
Lyon 291 describes common welding techniques and variables and the relative radiation exposure from each. These variables and their impact on UVR are summarized in Table 3.
UVR is associated with arc welding processes which include manual metal arc, gas metal arc (GMA) and gas tungsten arc welding. GMA welding generally produces the most radiation of the common welding processes and aluminium is generally welded by GMA welding. (Table 4)
It should be noted that not all welding processes involve striking an arc. These forms of welding produce minimal UVR. Welding processes and their UVR emissions are summarized in Table 5.
Skin protection is essential to minimize UVR exposure. Suitable protection while arc welding includes wearing suitable gloves as well clothing over the arms and forearms down to the gloves. For welding trades-people working in an uncomfortable environment, operator comfort and convenience are a major factor. In particular, the radiant heat from welding can be quite uncomfortable and welding on a hot day compounds the problem. The temptation is to discard heavy welders’ clothing in favour of light, summer clothing. The wearing of short sleeved shirts and / or no gloves while welding places the skin of the forearm and hand at considerable UVR exposure. Many welders recognize the red triangle that develops over the manubrium. This erythema commonly results from the welder forgetting to fasten the top shirt buttons before welding.
Aside from full time welders, there are many trades-people who perform welding as a small part of their occupation (eg; motor mechanics) and these people often find it inconvenient to put on protective clothing in order to undertake a quick job.
A third group of welding workers, sculptors and trades-people doing highly intricate work, also experience difficulties in achieving fine details with heavy clothing over their forearms and thick gloves on their hands.
Furthermore, while trades-people are invariably educated in health and safety issues when learning to weld, other workers in the same workplace may not be. It is common to see welders working in a factory with thick clothing and a suitable mask while other people in the vicinity have little or no skin protection. Sometimes these are assistants supporting the metal being fused. Exposure to UVR of all people working in the area of a welding arc should be considered.
While there remain many unanswered questions regarding arc welding and skin cancer risk, there are some principles that we can consider in prevention of skin cancer. These include:
When skin cancer patients deny a significant history of sun exposure, arc welding should be considered a possible cause.
Welders can be advised regarding appropriate clothing and be encouraged to choose sunscreens that include UVC protection. Workers welding aluminium risk the highest exposures to artificial UV and can be so advised.
The lack of quality studies means there is uncertainty about the risk of skin cancers from arc welding operations and further investigations are needed.
Issues that should be considered in any future study include:
· Examining workers who commenced welding at least 25 years prior to the study.
· Workers using varying arc welding processes, shielding gases and metals.
· Part time welders who do not adequately protect themselves.
· Examining for atypical naevi as well as actinic keratoses, NMSC and malignant melanoma.
· Obtaining histology on any suspicious lesions.
· Background actinic damage from solar UVR.
· Similarly, other risk factors such as skin type need consideration.