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Objectives: To study the mortality from lung cancer from exposures to hard metal dust at an industrial site producing hard metals--pseudoalloys of cobalt and tungsten carbide--and other metallurgical products many of which contain cobalt.Methods: A historical cohort was set up of all subjects who had worked for at least 3 months on the site since its opening date in the late 1940s. A full job history could be obtained for 95% of the subjects. The cohort was followed up from January 1968 to December 1992. The exposure was assessed by an industry specific job exposure matrix (JEM) characterising exposure to hard metal dust from 1 to 9 and other possibly carcinogenic exposures as present or absent. Smoking information was obtained by interview of former workers. Standard lifetable methods and Poisson regression were used for the statistical analysis of the data.Results: Mortality from all causes was close to the expected (standardised mortality ratio (SMR) 1.02, 399 deaths) whereas mortality from lung cancer was significantly increased among men (SMR 1.70; 46 deaths, 95% confidence interval (95% CI) 1.24 to 2.26). By workshop, lung cancer mortality was significantly higher than expected in hard metal production before sintering (SMR 2.42; nine deaths; 95%CI 1.10 to 4.59) and among maintenance workers (SMR 2.56; 11 deaths; 95%CI 1.28 to 4.59), whereas after sintering the SMR was lower (SMR 1.28; five deaths; 95%CI 0.41 to 2.98). The SMR for all exposures to hard metal dust at a level >1 in the JEM was in significant excess (SMR 2.02; 26 deaths; 95%CI 1.32 to 2.96). The risks increased with exposure scores, duration of exposure, and cumulative dose reaching significance for duration of exposure to hard metal dust before sintering, after adjustment for smoking and known or suspected carcinogens.Conclusion: Excess mortality from lung cancer was found among hard metal production workers which cannot be attributed to smoking alone. This excess occurred mostly in subjects exposed to unsintered hard metal dust. [ABSTRACT FROM AUTHOR]

A job exposure matrix (JEM) was developed by a committee of experts using the DELPHI method, in the French hard metal industry, in order to assess occupational exposures to cobalt along with tungsten carbide resulting from the industrial process. This JEM is part of a nested case-control study, carried out within the historical cohort of workers ever employed in these factories, aimed at assessing lung cancer risk. The committee included 8 experts: hygienists, chemical engineers, occupational physicians and epidemiologists. The JEM was developed in four stages: (i) visit of factories, (ii) definition of lines (job-periods) and columns (exposures) of the JEM, (iii) definition of coding procedures, (iv) coding the cells of the JEM. This last stage used a method derived from the DELPHI method. Throughout the study period 1945-1994. 320 job-periods and 21 agents were defined. A quantitative assignment (level 0 to level 9) along with a frequency code (1 to 3) was attempted for 4 agents, whereas only a qualitative assignment (non exposed/exposed, i.e. 0/l) was done for the other agents. An additional probability code (1 to 3) was assigned to all agents. This procedure led to 46 columns and 14,720 cells in the JEM. When applying the DELPHI method, the consensus of the committee was obtained for 85% of all cells after the first individual assignment of experts, 88% after the second individual assignment and 100% after the third assignment by the experts all together. In order to validate the JEM, these expert assignments will be brought together with the results of exposure measurements that were performed in some workplaces of these factories. The JEM will also be linked with the data base of the case-control study for the exposure assessment of cases and controls.