Letter to the Editor

Scand J Work Environ Health 1995;21(1):65-68    pdf

doi:10.5271/sjweh.10

Does welding stainless steel cause cancer?

by Marini F, Ferré M-P, Gross H, Mantout B, Huvinen M, Beaufils D, Cunat P-J, Bozec C

In his paper on the role of chemical species and exposure characteristics in cancer among persons occupationally exposed to chromium compounds, Langård (1) presents the welding of stainless steel as an activity potentially presenting a carcinogenic risk because of the presence of hexavalent chromium compounds in welding fumes. He supports this position directly from epidemiologic studies by the International Agency for Research on Cancer (IARC) (2) and Sjögren (3, 4). He also refers more indirectly to the studies by Becker (5, 6). We do not agree with his position or the interpretation he made of the results of the various studies in which the welding of stainless steel (which means potential exposure to hexavalent chromium) was specifically addressed by epidemiologists. The IARC study is certainly the most relevant and significant one. It was a multinational study carried out in nine European countries on 11092 mild steel and stainless steel welders. A distinction was made between four categories of welders according to potential exposure to hexavalent chromium (table 1). Table 2 contains standardized mortality ratios (SMR) on which comparisons can be made in relation to the statement made by Langård. It is surprising that Langård has concluded that the SMR of 157 for the "stainless steel welders 10 years of employment" was "indicating that stainless steel welders are more likely to die from lung cancer than welders as a whole [p 00]" without having reported any of the other figures available in the Simonato paper in relation to other categories of welders implied in the comparison, that is, 176 for "predominantly stainless steel welders" and, especially, 173 for "mild steel welders"! Any hypothesis of a role played by hexavalent chromium compounds in an excess of cancers was ruled out by Simonato in his conclusions: "The excess mortality from lung cancer is present among shipyard welders, mild steel welders, and stainless steel welders, but it does not appear to be related to duration of employment or cumulative exposure to total fumes, total Cr, Cr VI, or Ni [p 00]". The only conclusion which can be drawn from these figures is that the mild steel welders in this cohort were at higher risk of lung cancer than the stainless steel welders were. The SMR for lung cancer among welders as a whole, when all the relevant studies are considered together, is on the order of 140. The cause of this excess is attributed by most experts first to asbestos and then to smoking. It should be remembered that there were five mesotheliomas observed in the European cohort. These two biases are also addressed in the Simonato paper. KH Jöckel, reporting on a case-referent study on lung cancer and welding in Germany concluded: "The present study supports the hypothesis that some, if not all, of the excess of risk observed in the literature may be due to exposure to asbestos [p 00]" (7). The lack of clear evidence for a role of the "stainless" characteristic of the steel in the excess of lung cancers can also be demonstrated by considering the following three studies made on subcohorts of the IARC/European cohort: the Swedish by Sjögren (3, 4), the German by Becker (5, 6), both quoted by Langård, and the French by Moulin (8), not quoted by Langård. Sjögren found five cases of lung cancer versus 2.5 expected. This low number of cases is not sufficient for a generalization. Asbestos was also involved. Becker, in 1985 and 1991, published the following results of a German cohort of 1213 welders of stainless steel: 1985 6 cases (SMR 95), 1991 14 cases (SMR 113) with the additional observation of three mesotheliomas attributed to the presence of asbestos. Since no statistically significant excess of lung cancer was found for these stainless steel welders, any role of chromium (or nickel) remains unsupported. Becker himself has written: "Lung cancer mortality only weakly increased after the removal of the effects of smoking and a part of the elevation must clearly be attributed to asbestos exposure . . . Thus the second follow-up of the German welder' s study does not yet allow final conclusions [p 00]". Among a French cohort of 2721 welders (all types of welding) Moulin found an SMR of 124 (19 cases) for all welders, an SMR of 159 (9 cases) for mild steel welders, SMR of 92 (3 cases) for stainless steel welders, and an SMR of 103 (2 cases) for "predominantly Cr VI." -- figures consistent with the aforementioned ones. Overall, we are supported by the statement by IARC in its monograph no 49 (9) (also cited by Langård as reference 10 in his paper): "A large European cohort study, including three cohorts reported previously, detected statistically significant increases in both the incidence of and mortality from lung cancer but demonstrated no consistent difference in cancer risk among stainless-steel welders as compared to mild-steel welders or to shipyard welders. In addition, five deaths were due to mesothelioma [p 00]." IARC also placed this industrial activity in group 2B of its categories for carcinogens as follows: "There is limited evidence in humans for the carcinogenicity of welding fumes and gases . . . . Welding fumes are possibly carcinogenic to humans (group 2B) [p 00]."