A multicentre cohort of 11 092 male welders from 135 companies located in nine European countries has been assembled with the aim of investigating the relation of potential cancer risk, lung cancer in particular, with occupational exposure. The observation period and the criteria for inclusion of welders varied from country to country. Follow up was successful for 96-9% of the cohort and observed numbers of deaths (and for some countries incident cancer cases) were compared with expected numbers calculated from national reference rates. Mortality and cancer incidence ratios were analysed by cause category, time since first exposure, duration of employment, and estimated cumulative dose to total fumes, chromium (Cr), Cr VI, and nickel (Ni). Overall a statistically significant excess was reported for mortality from lung cancer (116 observed v 86-81 expected deaths, SMR = 134). When analysed by type of welding an increasing pattern with time since first exposure was present for both mild steel and stainless steel welders, which was more noticeable for the subcohort of predominantly stainless steel welders. No clear relation was apparent between mortality from lung cancer and duration of exposure to or estimated cumulative dose of Ni or Cr. Whereas the patterns of lung cancer mortality in these results suggest that the risk of lung cancer is higher for stainless steel than mild steel welders the different level of risk for these two categories of welding exposure cannot be quantified with precision. The report of five deaths from pleural mesothelioma unrelated to the type of welding draws attention to the risk of exposure to asbestos in welding activities.The first study reporting an increased risk for lung cancer among welders was the case-control study by Breslow et al.' Since that time, several case-control studies of lung cancer have reported findings for welders,"' and a number of cohort studies of welders' mortality have been carried out."24 Most of these studies, along with several analyses of routine mortality data, have reported excesses of mortality from lung cancer ranging from 30% to 50%. Few studies, however, have investigated the potential carcinogenic effect of exposures to specific welding fumes.They have been reviewed by Peto" and by the International Agency for Research on Cancer (IARC).26 Welders are exposed to welding fume, which in the case of stainless steel welding contains the carcinogens nickel (Ni) and chromium (Cr). Also, some welders are at risk of exposure to asbestos (particularly in shipyards) and suspected carcinogens such as silica dust.27 Many earlier studies did not subdivide welders by type of exposure; therefore the major aim of this study has been the separation of stainless steel welders, potentially exposed to Cr and Ni, from mild steel welders and welders in shipyards. This historical prospective study is unable, as in most such studies, to measure the potential confounding effect of smoking habits.The IARC coorganised with the European Regional Offiice of the World Health Org...

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The proportion of lung cancer due to occupational exposure has been estimated by computing the attributable risk in the population (ARp) from various case-control studies. Different criteria have been used in including occupational exposures from published studies: (i) exposure to lung carcinogens according to a job-exposure matrix approach; (ii) occupations in which an increased risk of lung cancer has been established; (iii) occupations in which an increased risk of lung cancer has been suggested; and (iv) occupations associated with a statistically significant increase of lung cancer. Only studies in which the confounding effect of smoking was controlled for have been included. We found a wide variability of ARp estimates, mainly due to the different geographical locations of the studies, while they seem to be only moderately affected by the different criteria of inclusion of the relevant occupational exposures. Studies using job-exposure matrices gave ARps ranging from 0.6% to 35%. When a list of recognized carcinogenic exposures was used for the selection of the relevant occupations, the estimates varied between 2.4% and 40%. From the studies reviewed it also appears that tobacco smoking has a very limited confounding effect. Various limitations of the exercise are discussed.

FLETCHER AC, ADES A. Lung cancer mortality in a cohort of English foundry workers. Scandj work environ health 10 (1984) 7-16. A cohort of males who started work between 1946 and 1965 inclusive in nine English steel foundries and who worked in these foundries at least one year has been followed prospectively until 1978. Mortality from lung cancer was significantly raised among workers employed in the foundry and fettling shop areas (standardized mortality ratios 142 and 173, respectively). Most occupational categories in these two areas had more lung cancer deaths than expected, but the standardized mortality ratios were the largest for the furnace bricklayers, fettlers, and heat treatment furnacemen. There was some evidence of risk increasing with length of employment. There were marked differences in the standardized mortality ratio for lung cancer between study foundries. By year of entry the lung cancer risk was fairly constant, in contrast to the improvement in mortality from diseases of the respiratory system over the same period.

A welding process exposure matrix has been developed relating 13 welding process-welded metal combinations to average exposure levels for total welding fumes, total chromium, chromium (VI) and nickel. Quantitative estimates were derived from consultation of literature sources and of some company data. This matrix was applied to the welding histories of 11,092 welders in the framework of an IARC multicentre study. When detailed welding history was not available at the individual level the average company welding practice profile was applied. No dose-response relationship emerged for lung cancer risk with cumulative dose of the carcinogens chromium (VI) and nickel for stainless steel welders. Dilution of the dose-response relationship could result from between-plant and within-plant variability, and exposure in jobs not accounted for in the study, but not from the partial use of company versus individual data. It is also possible that there is no increased risk related to chromium and nickel exposure in this group of workers. Matrix exposure estimates would need to be validated and the matrix possibly refined by comparison with a variety of comprehensive welding exposure data sets.