Biomedical subjects
Publications and source records attributed to S Langård.
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The total mortality and the incidence of cancer was studied among a cohort of employees at the six oldest ferrosilicon and ferromanganese plants in Norway. The cohort consisted of 6494 men employed for more than 18 months before 1970 and has been followed up from 1953 to 1982. The standardised incidence ratio (SIR) for cancer (all sites) was 0.94. The observed number of cancers was as expected for lung cancer (SIR = 0.99) and for most of the other cancer sites studied. A statistically significant reduction of stomach cancer was found (SIR = 0.72). There was an increased incidence of lung cancer (SIR = 1.75) and cancer of the prostate (SIR = 1.56) in the workers at one ferrosilicon plant and of colonic cancer (SIR = 1.90) at another ferrosilicon plant.
The overall mortality and the incidence of cancer have been studied among male employees at a plant producing calcium carbide. The cohort was defined as all men employed at the plant for at least 18 months in the period 1953 to 1970 and was classified according to 10 occupational categories. The 790 men have been observed from 1953 to 1983 and the incidence of cancer in the cohort has been compared with national incidence rates. A significant excess of colonic cancer (standardised incidence ratio, SIR = 2.09) and of prostatic cancer (SIR = 1.78) was found, and also a slight excess of lung cancer among furnace and maintenance workers (SIR = 1.56). The possible exposure of the workers to polycyclic aromatic hydrocarbons, asbestos, and cadmium is discussed.
A cross-sectional population study. Scand J Work Environ Health 12 (1986) 561-566. In order to study the number of persons previously exposed to asbestos in the general population, an investigation with a self-administered questionnaire and a screening with 10 X 10-cm chest radiographs was conducted among 28,216 men aged 40 years and over in nine municipalities in the county of Telemark, Norway. Among the 21,453 subjects who answered the questionnaire in the primary screening, 3,888 (18.1%) reported previous occupational exposure to asbestos. Of the exposed subjects 2,368 (61.4%) were less than 60 years of age, and 2,611 (69.9%) had been exposed for the first time after 1950. In regard to the degree of exposure, 77.7% considered their previous exposure to be light. Past and present smoking habits were recorded for all the subjects, and a high-risk group of 1,734 subjects with past exposure to asbestos and present smoking was identified. Approximately 270 incident cases of lung cancer can be expected among the 21,453 study subjects during the next 10 years, and it is estimated that about 110 of these cases will occur in the high-risk group with combined asbestos-cigarette exposure.
The proportion of lung cancer related to occupational exposure to respiratory carcinogens and other workplace contaminants has been studied in a hospital-based case-referent study of 176 incident cases and 176 referents, recruited from the medical ward of two county hospitals in southern Norway. On the basis of job title and exposure information, three different approaches for the estimation of etiologic fraction were used, all based upon a trichotomous categorization of the exposure variable. Among the definitely exposed subjects, the etiologic fraction for lung cancer related to occupational exposure factors was from 22 to 35%, increasing to 37-47% when the "possibly exposed" categories were included. When asbestos was the only factor to be eliminated, the etiologic fraction estimate suggested a 23% reduction in the lung cancer incidence in the study population. More than 90% of the lung cancer cases would theoretically have been prevented if smoking had been completely removed. The relative merits of preventing one or several of the study factors simultaneously is discussed.
In a hospital-based case-referent study of 176 incident lung cancer cases, ascertained during a five-year period from two county hospitals, the role of asbestos exposure and smoking has been studied. Information on asbestos exposure was obtained from personal interviews, and allocated to four exposure categories, according to the intensity and duration of the exposure. Twenty-five percent of the cases and 10% of the referents had been moderately to heavily exposed to asbestos during their working career. A statistically significant trend in risk ratio related to the degree of exposure was observed, with a more than fourfold risk among the heavily exposed. The strongest association was found between asbestos exposure and small cell carcinoma, and the weakest association between asbestos exposure and adenocarcinoma. Very high risk ratios were observed among asbestos-exposed subjects who were heavy smokers, and the interaction observed between asbestos and smoking conformed more closely to a multiplicative model than to an additive one. The results suggest that the observed association between lung cancer and occupational exposures in this study was, to a large extent, due to asbestos exposure. Information on such exposure was missing in 90% of the medical records of these patients.
The role of occupational exposures and smoking in the development of lung cancer has been studied among 176 male incident lung cancer cases and 176 referents admitted to two county hospitals in southeast Norway during 1979-1983. After the allocation of all occupational titles in the Nordic Classification of Occupations into three exposure groups according to potential exposure to respiratory carcinogens and other contaminants, each subject was classified according to exposure status of main occupation and number of years in each exposure category. An excess risk of lung cancer was observed both among those in possibly exposed occupations and among those definitely exposed. A more than threefold excess risk was observed among subjects with more than 30 years in exposed occupations. Exposure to 22 agents/processes was further assessed by a separate questionnaire and estimated simultaneously in a logistic regression model. Elevated risks were associated with exposure to asbestos and several other agents/processes, which largely correlated to each other. Smoking was strongly associated with all histological subtypes of lung cancer, while for occupational exposures the risk ratio was highest for small cell carcinoma and lowest for adenocarcinoma. Very high risk ratios for lung cancer were observed among heavy smokers in exposed occupations.
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The incidence of cancer was studied in a cohort of 287 men who were exposed to asbestos at a nitric acid production plant from 1928 onwards. During the observation period from 1953 through 1980 all cancer cases among the cohort members were identified in The Cancer Registry. For the whole cohort 42 cases of cancer were observed versus 30.6 expected. The figures for cancer of the lungs and pleura combined were 17 observed versus 3.7 expected. The corresponding figures for a heavily exposed subcohort were 11 observed and 1.2 expected. In that group there was also an increased incidence of colon cancer with 3 cases observed against 0.8 cases expected. Within the whole cohort four cases of pleural and one case of peritoneal malignant mesothelioma were found. There was also an increased incidence of malignant melanoma of the skin with 3 cases observed against 0.6 expected. For cancer cases that were registered as of unknown origin there were 7 cases observed and 1.4 expected. There was no increased rate ratio for cancer at any site before 20 years after the first asbestos exposure. The smoking habits of all cohort members were recorded and the relative rates for lung cancer were calculated in relation to smoking habits. In common with previous studies the results indicate a multiplicative model for the interaction between asbestos exposure and smoking in regard to lung cancer risk.
The aim of this study was to investigate the incidence of cancer among 318 male employees of a niobium mining company which was only operated between 1951 and 1965. Many of the workers, especially underground miners, were exposed to the daughters of radon and thoron and also to thorium. The accumulated doses to the workers from short-lived radon and thoron daughters in the mine atmosphere were assessed to be relatively low; up to 300 working-level months. During the follow-up period 1953-1981, 24 new cases of cancer were observed compared to an expected number of 22.8. Twelve cases of lung cancer had occurred versus 3.0 expected. Among the 77 miners, 9 cases of lung cancer were observed against 0.8 expected. Associations between the occurrence of lung cancer and exposure to alpha radiation and smoking were found. For the radon and thoron daughter exposure, about 50 excess cases per million person-years at risk per working-level month were observed.
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Although the high exposures to metallic aerosols that were formerly encountered in the primary nickel industry are no longer prevalent, large occupational groups, such as welders, are currently exposed to moderate levels and may therefore be at some degree of health risk. Examination of the world literature reveals a number of epidemiological studies which demonstrate a slight excess risk of respiratory tract cancer incidence among the general welding population. Several of these studies are suggestive of the possibility that there may be a larger excess risk exclusively limited to those welding cohorts who are exposed to nickel and chromium in the fumes from the welding of stainless and high alloy steels. Such a hypothesis, although supported in part by in vitro and in vivo genotoxicity tests, can only be verified by international collaboration in specifically designed epidemiological studies using a uniform protocol.
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The results of a follow-up study on the incidence of lung cancer in 133 workers producing zinc chromate pigments are presented. By the end of 1972 three cases of lung cancer had occurred in a sub-cohort of 24 workers who had been employed for over three years. The same group of workers has now been followed up to December 1980 and three further cases of lung cancer were found. The observed/expected ratio was 44 in this group, virtually the same as at the end of 1972. Five of the six patients smoked. Only one had been exposed to chromates other than zinc chromates.
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The possible association between selected cancers and polluted work places has been studied in a hospital-based, case-control study. By dividing all jobs in the participants working career into "polluted" and "clean", a crude measure for the total industrial exposure a worker experiences throughout his life was established. Among 103 age-matched, case-control pairs the overall estimated relative risk (RR) for exposed subjects (greater than or equal to 10 years in a polluted work place) of developing cancer compared to nonexposed (less than 10 years in a polluted work place) was 1.1. The only subgroup where a significant difference was found between the cases and the controls was the lung cancer subgroup (RR = 4.0, p = 0.02, two-tailed). When the 30 lung cancer cases were compared to an alternative control group consisting of 60 subjects matched for age and smoking habits, an estimated RR of 4.5 was found. A moderate, but not significant association between lung cancer and definite asbestos exposure was also found (RR: 2.3). As most workers are exposed to a variety of industrial agents throughout their working careers, further development of methods for characterizing combined exposures are needed, both for retrospective and prospective purposes.