OBJECTIVE--The objective of this study was to provide an extended follow-up of workers in three Swedish plants producing man-made vitreous fibers (MMVF). METHOD--Mortality and cancer incidence was investigated among 3539 male and female workers, employed for at least one year before 1978. Mortality was followed from 1952 to 1990 and cancer incidence from 1958 to 1989. National and regional mortality and cancer incidence rates were used to calculate the expected numbers. RESULTS--Twenty-seven lung cancer deaths were observed compared with 23 expected (standardized mortality ratio 117, 95% confidence interval 81-176), based on regional mortality. With a latency time of 30 years, the lung cancer risk was significantly elevated, but not trend was found for the standardized mortality ratio with increasing duration of exposure to MMVF. The lung cancer and stomach cancer mortality was higher in the rock wool industry than in the fiber glass industry. Fiber exposure from 1938 to 1990 was estimated in the two rock wool plants by applying a model for historical fiber exposure estimation, specific for different job titles in the rock wool production industry. No relationship was found between individually cumulated rock wool fiber exposure and lung cancer or stomach cancer risk. CONCLUSIONS--The numbers of lung cancers and stomach cancer cases were low and did not therefore allow more general conclusions regarding the cancer hazard for exposed workers. A large European study in progress will probably allow more precise conclusions.
We have updated the follow-up of cancer mortality for a cohort study of man-made vitreous fiber production workers from Denmark, Finland, Norway, Sweden, United Kingdom, Germany, and Italy, from 1982 to 1990. In the mortality analysis, 22,002 production workers contributed 489,551 person-years, during which there were 4,521 deaths. Workers with less than 1 year of employment had an increased mortality [standardized mortality ratio (SMR) = 1.45; 95% confidence interval (CI) = 1.37-1.53]. Workers with 1 year or more of employment, contributing 65% of person-years, had an SMR of 1.05 (95% CI = 1.02-1.09). The SMR for lung cancer was 1.34 (95% CI = 1.08-1.63, 97 deaths) among rock/slag wool workers and 1.27 (95% CI = 1.07-1.50, 140 deaths) among glass wool workers. In the latter group, no increase was present when local mortality rates were used. Among rock/slag wool workers, the risk of lung cancer increased with time-since-first-employment and duration of employment. The trend in lung cancer mortality according to technologic phase at first employment was less marked than in the previous follow-up. We obtained similar results from a Poisson regression analysis limited to rock/slag wool workers. Five deaths from pleural mesothelioma were reported, which may not represent an excess. There was no apparent excess for other categories of neoplasm. Tobacco smoking and other factors linked to social class, as well as exposures in other industries, appear unlikely to explain the whole increase in lung cancer mortality among rock/slag wool workers. Limited data on other agents do not indicate an important role of asbestos, slag, or bitumen. These results are not sufficient to conclude that the increased lung cancer risk is the result of exposure to rock/slag wool; however, insofar as respirable fibers were an important component of the ambient pollution of the working environment, they may have contributed to the increased risk.
This report gives an account of the Swedish contribution to the joint European epidemiologic study on production workers in the man-made mineral fiber (MMMF) industry. The information sources utilized and the follow-up procedure, making extensive use of record-linkage operations extracting data from computerized data banks, are described in some detail. The follow-up with regard to vital status, deaths and causes of death, diagnosed cancers, and emigration could essentially be based on such techniques. The problems of tracing immigrant and emigrant subpopulations are given particular attention. The exposed Swedish cohort consisted of 3,600 persons giving 61,690 person-years of observation. A total of 524 deaths was observed in the cohort, 230 cohort members had emigrated during the period of observation (147 of whom could be traced to other Nordic countries), and 62 other persons were lost to follow-up. It was observed that most of the persons contracting lung cancer in the Swedish cohort had been exposed during relatively short periods of time, ie, during one to four years of employment. This finding applied to both the rock-wool and glass-wool industry. The authors point out that the observed excess risk in lung cancer deaths may also have other explanations than occupational exposure to MMMF.