In order to investigate the prevalence of asbestos-related diseases, a cross-sectional population study was conducted among 28,216 men aged 40 years in nine municipalities of the county of Telemark, Norway. In a primary radiographic screening 10 X 10-cm chest radiographs were taken of 21,483 persons. In two independent readings of the radiographs, pleural changes were observed in 6.9 and 8.5% of the study subjects. Radiographic findings in the primary screening led to 1,431 subjects being selected for a reexamination. On the basis of occupational histories and 40 X 40-cm chest radiographs, it was concluded that 470 of these subjects (2.2% of the screened population) had radiographic changes consistent with an asbestos-related disorder. Among these, 86 had lung fibrosis (82 in combination with pleural plaques) and 384 had pleural plaques only. There were marked differences in the occurrence of asbestos-related disorders between the seven urban and two rural communities studied, and agreement was observed between the occurrence of such disorders and the degree and duration of the reported asbestos exposure. The study presents evidence that asbestos-related disorders may be more prevalent in the general male population than has been recognized earlier.
A sample of 1388 10 x 10 cm chest X-rays from a previous population screening of males aged 40+ years were reevaluated by use of the ILO classification. There were 1036 films of subjects from an industrialized town, and 352 from a rural community. The observed rates of parenchymal changes (profusion > or = 1/0) at the reevaluation were 1.3% in the urban community and 3.4% in the rural community. The corresponding figures for pleural changes were 5.0% and 0.6%, respectively. Based on additional questionnaire information on asbestos exposure, it was found that the radiographic changes were probably related to past asbestos exposure for 2.3% of the subjects from the urban community and 0.6% from the rural community. In cases of asbestos-related illnesses the mean time since first exposure to asbestos was 35.9 years, whereas the mean duration of the exposures was 11.4 years. The results seem to indicate that the ILO reassessment of the radiographs was more sensitive in detecting pleural changes than the previous clinical screening of both small and large films.
A previous study on the incidence of cancer in a cohort of 286 asbestos-exposed electrochemical industry workers observed from 1953 through 1980 has been extended with another 8 years of follow-up. The incidence of cancer was derived from the Cancer Registry of Norway, and the expected figures were calculated by a life table method. During the extended follow-up period from 1981 through 1988, among the cohort members there were 12 new cancer cases versus 14.2 expected (SIR 85, 95% CI 44-158). In a lightly exposed sub-cohort, the extended follow-up revealed 4 cases of lung cancer or pleural mesothelioma (ICD, 7th revision 162-163) versus 1.6 cases expected (SIR 256, 95% CI71-654). In a heavily exposed sub-cohort, the corresponding figures were 3 and 0.5 (SIR 588, 95% CI 118-1,725).
The findings of a previous chest X-ray screening, determined without using standardized criteria, were reassessed by means of the ILO classification. Of 470 radiographs that had been determined as showing asbestos-related changes, 430 were categorized according to the ILO Classification. Small opacities with profusion greater than or equal to 1/0 were described in 39 (52%) of 75 participants who, on the original clinical reading, had been determined as having lung fibrosis, and in 45 (12.7%) of 355 who were determined as having pleural changes only. When considering circumscribed pleural thickening at the chest wall or diaphragm, as categorized by the ILO Classification, such changes were present in 401 (93.7%) of 428 subjects with pleural changes as determined on the clinical reading. In addition to the improved sensitivity and specificity achieved, the ILO Classification also allows comparison with other studies. The most apparent disadvantage of the ILO system is that it cannot firmly separate the various types of asbestos-related pleural changes. The study revealed that the previous asbestos exposure of the case subjects had occurred in many different workplaces and occupations.
Prevalence of disease related to previous exposure to asbestos was investigated in a cohort of 394 men who had worked for more than a year at a magnesium plant before 1970. Radiography showed lung fibrosis in nine men (2.3%) and pleural plaques in 40 men (9.5%). Prevalence rates varied considerably between sub-groups subjected to different modes of exposure. For the whole cohort there was a positive correlation between prevalence rate of radiographic changes and duration of work entailing exposure to asbestos. Subjects with pleural changes had more dyspnoea than found in an external reference material. Vital capacity and forced expiratory volume in one second was significantly reduced for the whole cohort. A significant reduction in lung function was found among a larger proportion of subjects with pleural changes than among subjects with no radiographic indications of such changes. The results unveil a need for similar surveys among workers in other energy-intensive industries where a similar mode of exposure to asbestos may be assumed.
OBJECTIVES: A Norwegian coke plant that operated from 1964 to 1988 was investigated to ascertain whether the male workers in this plant had increased morbidities of cancer or increased mortality from specific causes, particularly associated with specific exposures at the coke plant. METHODS: Personal data on all the employees of the plant were obtained from the plant's archives. With additional data from the Norwegian Bureau of Statistics we identified 888 male former workers at the plant. Causes of death were obtained from the Norwegian Bureau of Statistics, and cancer diagnoses from the Norwegian Cancer Registry. The results were compared with national averages adjusted for age. Specific exposures were estimated with records of actual measurements done at the plant and interviews with former workers at the plant. RESULTS: A significant excess of stomach cancer (standardised incidence ratio (SIR) 2.22, 95% confidence interval (95% CI) 1.01 to 4.21) was found. Mortality from ischaemic heart disease and sudden death was positively associated with work in areas which entailed peak exposures to CO. When considering work in such areas the past 3 years before death, the association was significant (p = 0.01). The last result is based on only two deaths. CONCLUSIONS: Considering the short follow up time and the small size of the cohort the results should be interpreted with a certain caution. The positive results would justify a re-examination of the cohort at a later date.
About 20% of al lung cancers among men are attributable to occupational exposure. During the years 1991 through 1993, Norwegian doctors reported 161 (4.6%) of 3.510 incidents of cancer in Norwegian men to the Labour Inspection as probably caused by occupational exposure. The proportion of such assumed occupational lung cancer cases varied with geographical region from 0.7% to 6.7%. Notification of an occupational cancer can be justification for economic benefits to the patient and his/her family. The most common assumed causes of the 161 cases notified as occupational lung cancers were asbestos dust exposure (148 cases), exposure to nickel (21 cases), and exposure to stone dust containing crystalline silica (18 cases). The predominating occupations of the patients at the time of the assumed carcinogenic exposure were machinist, industrial worker in metallurgical or chemical industry, mechanic, or metal worker (metal sheet worker, welder).
The prevalence of respiratory symptoms and lung function impairment was studied in a sample of men from a population screening of asbestos-related disorders. When the rates were adjusted for age and smoking habits, 83 subjects with lung fibrosis had an increased prevalence of respiratory symptoms, in particular, phlegm when coughing and breathlessness grades 1-3. Among 200 subjects under 70 years of age who had pleural plaques only, a statistically significant increase was observed in the prevalence of breathlessness grade 1 compared to an external reference population. Among 98 asbestos-exposed subjects who had normal chest X-rays, there was an increase in the prevalence of breathlessness grade 2, cough during the day, and phlegm when coughing. There was a higher proportion of subjects with lung fibrosis who were below 80% of the predicted values for forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) than in the other groups. There was also a higher proportion of subjects with pleural plaques only who were below 90% of the predicted value for FVC than in a group of 90 subjects without asbestos exposure. In accordance with previous studies, these results indicate that pleural plaques in asbestos workers may be of greater importance as a clinical feature than has been recognized in the past.
The purpose of this study was to examine respiratory symptoms and lung function (forced vital capacity [FVC] and forced expiratory volume in 1 second [FEV1]) as related to changes in smoking habits in subjects previously exposed to asbestos. The study was linked to a smoke-ending program among asbestos-exposed males. Subjects were recruited from a population-based survey, and 231 smokers met for the baseline consultation. The baseline prevalences of cough, chronic cough, and dyspnea among smokers were 68.0%, 44.6%, and 42.4%, respectively. Both smoke-ending (n = 10) and tobacco reduction (n = 52) during the 2-year follow-up resulted in remission of cough and chronic cough, whereas dyspnea was unaffected. When the 2-year measurements of FVC and FEV1 were adjusted for the respective baseline measurements, FEV1 tended to improve in subjects who had quit during the study, relative to the continuing smokers. It was concluded that both smoke-ending and reduction of tobacco consumption resulted in reduction of cough and chronic cough, but not of dyspnea. The study further suggests a possible positive effect of smoking cessation on FEV1, but not merely by reduction of tobacco consumption.