Mortality among employees of an Ontario factory manufacturing insulation materials from amosite asbestos

The mortality of workers from an Ontario factory manufacturing amosite asbestos insulation materials under poorly controlled environmental conditions is reported here. Seven (58%) of 12 deaths among exposed workers 10 or more years after first exposure were due to malignancies; four (25%) were from lung cancer, and there were two deaths from peritoneal mesothelioma. Those dying from mesothelioma were 47 and 49 years of age. Three (25%) of 12 deaths were from respiratory disease, two were attributed to asbestosis (in men 42 and 53 years of ages), and one to pneumonia in a 54-year-old male.     

Mortality experience of glass fibre workers.

A historical prospective mortality study was conducted at an insulating wool plant in Ontario, Canada, on 2576 men who had worked for at least 90 days and were employed between 1955 and 1977. Eighty eight deaths were found in the 97.2% of men traced. Mortality was compared by the person-years method with that of the Ontario population. Measurements taken since 1977 show very low fibre concentrations. The overall standardised mortality ratio (SMR) was 78%, significantly below 100. Among plant only employees, seven deaths were attributed to lung cancer compared with 4.22 expected, a non-significant excess (SMR = 166; 95% confidence limits 67 to 342). No confirmed cases of mesothelioma were observed and no other disease was significantly increased in plant workers.     

The mortality of amphibole miners in South Africa, 1946-80.

A cohort was established in 1981 of all 7317 white male employees in the amosite and crocidolite mines in South Africa whose names had appeared in the personnel records (initiated between 1945 and 1955) of the major companies. Some of the men had been employed as early as 1925, but only 8% had had more than 10 years of service. Three subcohorts were defined: 3212 men whose only exposure to asbestos was to amosite; 3430 exposed to crocidolite; and 675 to both amphiboles. No deaths or losses to view occurred before 1946, and 5925 men (81%) were known to be alive at the end of 1980. Losses to view numbered 167 (2%), and there had been 1225 deaths (17%), an excess of 331 over the number of deaths expected on the basis of the mortality of all white South African males. The fibre related excesses were of mesothelioma, lung cancer, and other respiratory diseases, but there were other excesses perhaps mainly related to socioeconomic factors including lifestyle. When cause of death was determined according to "best evidence" (after study of clinical, radiological, biopsy, and necropsy reports in conjunction with the death certificate), there were 30 deaths due to mesothelioma (22 pleural, six peritoneal, two other) and 65 due to cancer of trachea, bronchus, and lung. Various analyses of these deaths showed that crocidolite had higher toxicity than amosite for lung cancer and this was most pronounced for mesothelioma; there can now be no question that crocidolite is far more dangerous than amosite at least in so far as mesothelioma is concerned. Nevertheless, crocidolite induced mesothelioma appeared only in men who had been exposed for long periods, at least 12 months, but on average about 15 years.     

The mortality of amphibole miners in South Africa, 1946-80.

A cohort was established in 1981 of all 7317 white male employees in the amosite and crocidolite mines in South Africa whose names had appeared in the personnel records (initiated between 1945 and 1955) of the major companies. Some of the men had been employed as early as 1925, but only 8% had had more than 10 years of service. Three subcohorts were defined: 3212 men whose only exposure to asbestos was to amosite; 3430 exposed to crocidolite; and 675 to both amphiboles. No deaths or losses to view occurred before 1946, and 5925 men (81%) were known to be alive at the end of 1980. Losses to view numbered 167 (2%), and there had been 1225 deaths (17%), an excess of 331 over the number of deaths expected on the basis of the mortality of all white South African males. The fibre related excesses were of mesothelioma, lung cancer, and other respiratory diseases, but there were other excesses perhaps mainly related to socioeconomic factors including lifestyle. When cause of death was determined according to "best evidence" (after study of clinical, radiological, biopsy, and necropsy reports in conjunction with the death certificate), there were 30 deaths due to mesothelioma (22 pleural, six peritoneal, two other) and 65 due to cancer of trachea, bronchus, and lung. Various analyses of these deaths showed that crocidolite had higher toxicity than amosite for lung cancer and this was most pronounced for mesothelioma; there can now be no question that crocidolite is far more dangerous than amosite at least in so far as mesothelioma is concerned. Nevertheless, crocidolite induced mesothelioma appeared only in men who had been exposed for long periods, at least 12 months, but on average about 15 years.     

Insulation workers in Belfast. 3. Mortality 1940-66

Elmes, P. C., and Simpson, Marion J. C. (1971).Brit. J. industr. Med.,28, 226-236. Insulation workers in Belfast. 3. Mortality 1940-66. One hundred and seventy men were identified as making up the total population of insulation workers in Belfast in 1940. This is an analysis of all the information about deaths that has emerged from tracing these men up to the end of 1966. Five remain untraced, and the mortality experience of the remainder is compared with that of other men in Northern Ireland over the period. There were 98 deaths when only 37 were expected. The number of deaths occurring exceeded those expected throughout the period 1940-66 and the increase was statistically significant during the period 1950-55 and onwards. There was an especially high mortality (compared with other Northern Ireland males) due to cancer of the lung, mesothelioma of the pleura and peritoneum, cancer of the gastrointestinal tract, and fibrotic lesions of the lungs. The ratio of observed over expected deaths was 2·6 for all causes, 3·9 for all cancers, and 17·6 for cancers of the lower respiratory tract and pleura. Those men finally classified as dying from lung cancer showed evidence of lung fibrosis whereas those classified as dying from mesothelioma did not. Comparisons within the group failed to show any relationship between age at first exposure or duration of exposure and the excessive mortality. There were too few non-smokers to show the significance of smoking.     

An historical prospective mortality study of the Sarnia Division of Dow Chemical Canada Inc., Sarnia, Ontario (1950-1984)

We examined the mortality experience of 3,479 male Dow Canada employees who were employed at Sarnia Division for at least 12 continuous months during the years 1945 through 1983, utilizing the Canadian Mortality Data Base maintained by Statistics Canada, covering 1950-1984. We analyzed cause-specific mortality using male, age and calendar-year-adjusted death rates for Canada and Ontario. Total mortality was significantly below expectation whether the entire follow-up period (240 observed vs. 366.9 expected) or a 15-year latency period (171 observed vs. 290.4 expected) was considered. Statistically significant fewer observed deaths were found for all respiratory cancer, cancer of the bronchus and lung, circulatory disease, ischemic heart disease, cerebrovascular disease, digestive disease, cirrhosis and other liver disease and deaths due to accidents, poisonings and violence. The observation of three deaths due to mesothelioma, a rare cancer often associated with asbestos exposure, was a significant finding as was a statistically significant elevation of observed deaths in the category "other forms of heart disease".     

The Handling of Workmen’s Compensation Claims

Few data exist concerning the comparative neoplastic potential in man of the several kinds of asbestos. In particular, there has been no evidence concerning whether the amosite variety is carcinogenic. The matter is of practical importance, since amosite use in the United States has sharply increased. The mortality experience of a group of 230 men previously employed in an amosite asbestos factory was studied during the years 1960 through 1971. Total deaths were more than twice the number anticipated: 46.4 were expected, and 105 occurred. Some 14 deaths were due to asbestosis. Both lung cancer and mesothelioma were found in considerable excess. Two or three deaths from lung cancer were expected, and 25 occurred. There were five deaths from mesothelioma. Occupational exposure to amosite asbestos can be associated with serious cancer hazard; its continued industrial use requires rigorous control.     

Mortality of asbestos workers in England and Wales 1971-81

A national study of British asbestos workers is briefly described and the mortality experience of 31 150 male asbestos workers in England and Wales who had been medically examined at least once as part of that survey is presented. The survey population is divided into workers with occupational exposure to asbestos before the inception of the 1969 Asbestos Regulations and those who worked with asbestos only after 1969. Of the 1128 who had died, 897 had worked before 1969; 34 of the death certificates received for these men mentioned mesothelioma and for another nine asbestosis was reported in the absence of mesothelioma or lung cancer. A statistically significant excess of lung cancer (SMR 136) was found. For the post-1969 workers, one case of asbestosis and one case of mesothelioma were reported, but further investigation of these cases showed probable occupational exposure to asbestos many years before 1969. The time from first exposure for this section of the population is too short to exclude an excess of asbestos related disease. The most noticeable excess of asbestos related disease was seen among the insulation workers who had more than twice (SMR 256) the expected number of deaths from lung cancer, and for whom almost 10% of all death certificates mentioned mesothelioma. No excess of any alimentary tract cancer was found and the population showed a significant deficit of large bowel cancer mortality (SMR 54).     

Mortality of asbestos workers in England and Wales 1971-81.

A national study of British asbestos workers is briefly described and the mortality experience of 31 150 male asbestos workers in England and Wales who had been medically examined at least once as part of that survey is presented. The survey population is divided into workers with occupational exposure to asbestos before the inception of the 1969 Asbestos Regulations and those who worked with asbestos only after 1969. Of the 1128 who had died, 897 had worked before 1969; 34 of the death certificates received for these men mentioned mesothelioma and for another nine asbestosis was reported in the absence of mesothelioma or lung cancer. A statistically significant excess of lung cancer (SMR 136) was found. For the post-1969 workers, one case of asbestosis and one case of mesothelioma were reported, but further investigation of these cases showed probable occupational exposure to asbestos many years before 1969. The time from first exposure for this section of the population is too short to exclude an excess of asbestos related disease. The most noticeable excess of asbestos related disease was seen among the insulation workers who had more than twice (SMR 256) the expected number of deaths from lung cancer, and for whom almost 10% of all death certificates mentioned mesothelioma. No excess of any alimentary tract cancer was found and the population showed a significant deficit of large bowel cancer mortality (SMR 54).     

Mortality from Lung Cancer and Other Causes among Workers in an Asbestos Textile Factory

An account is given of work in an asbestos textile factory and of the steps taken to reduce exposure to dust since the introduction of the Asbestos Industry Regulations in 1931.

Measurements of the amount of dust to which men were exposed in the scheduled areas have been made by various methods since 1951, but the data obtained by these methods are not directly comparable. Measurements made since 1960 show that the mean yearly dust level has been fairly constant from year to year and has varied from place to place between 1 and 8 particles (5 to 100 microns long and at least three times as long as they were wide) per c.c. of air.

Chrysotile was used predominantly in the factory, but small amounts of crocidolite were also processed at all relevant periods.

Death rates have been recorded for all the 256 men who were employed for at least 20 years in the scheduled areas since the first man completed 20 years' exposure in 1916, and for the 538 men and 220 women who were employed for at least 10 years in the scheduled areas but were never employed in these areas before 1933.

The results show a substantially increased mortality for men who were exposed for 10 or more years before 1933 (48 deaths from all causes against 17·1 expected).

The increased mortality among these men can be accounted for by an increased mortality from cancer of the lung (12 deaths against 1·2 expected) and from diseases of the respiratory and circulatory systems associated with asbestosis.

Men employed before 1933, but for less than 10 years, showed an increased mortality from lung cancer (5 deaths against 2·6 expected), but no significant increase from other causes. Men and women who were exposed only since January 1, 1933, have had a mortality experience close to the national average.

Analysis of the trends in mortality shows (1) a decrease in mortality from lung cancer and other deaths associated with asbestosis with reduction in length of employment before 1933, and (2) an increase in mortality from lung cancer and other deaths without asbestosis with age.

Twenty-three cases of lung cancer occurred in men who had been employed in the scheduled areas for at least 20 years. One was regarded as a pleural mesothelioma and the rest (approximately 18 in excess of expected) appear to have been ordinary bronchial carcinomas.

Four other mesotheliomas have been diagnosed since 1963, all in men and women with less than 10 years' exposure, one with only seven months' exposure, and one in a man who had been employed in the scheduled areas only since 1937.

The results provide grounds for believing that the occupational hazard of bronchial carcinoma has been largely eliminated, but the data are insufficient to estimate the extent of the risk which may remain.

     

A follow-up study of agricultural chemical production workers.

This retrospective follow-up study evaluated the mortality experience of 4,323 men employed at a plant in Alabama (AL) that manufactures agricultural and other chemicals. On average, there were 18 years of follow-up per subject during the study period of 1951 to 1987. The observed numbers of deaths among cohort members were compared with the numbers expected on the basis of United States (US) and AL general population mortality rates. The all causes standardized mortality ratio (SMR), computed using US rates as the referent, was 97 (233 observed/240 expected deaths) for whites and 68 (47/69) for blacks. White subjects had more than expected deaths from buccal cavity and pharynx (BCP) cancer [SMR = 388; 95% confidence interval (CI) = 125-905] and from esophageal cancer (SMR = 417; 112-1,067). Their lung cancer mortality rate was 50% higher than the rate of US white men and 14% higher than the rate of AL white men. Each of these three cancers has strong nonoccupational determinants, the roles of which were not assessed and which may have been responsible in whole or in part for the observed increases. The excesses of lung and esophageal cancer were concentrated among short-term employees, an observation which also argues against a causal link with occupational factors. Black men experienced no increased mortality from BCP, esophageal or lung cancer, but results for blacks were imprecise. For white and black subjects combined, there were 3 observed versus 0.62 expected deaths due to soft tissue sarcoma (p = 0.05). The job histories of subjects with this type of cancer did not suggest any shared occupational exposure.     

Mesothelioma and asbestos in the Province of Quebec, 1969-1972

All records of patients who died of mesothelioma in the Province of Quebec during the period 1969-1972 were collected and reviewed. Asbestos exposure in this group was compared with that in two control groups, one of persons dying of accidental causes and the other of those dying of cardiovascular disease. The mortality rate for mesothelioma was estimated at between 2.3 and 2.8 per million per year. Men were affected twice as frequently as women, this difference being related exclusively to pleural mesothelioma. The incidence in urban regions was much higher than in rural areas, and areas involved in mining showed an incidence in the expected range. Thirty-four percent of the patients with mesothelioma and only 2% of controls had histories of direct exposure to asbestos. This exposure was related to asbestos processing and not its production. No woman gave a history of occupational exposure to asbestos. It appeared that chrysotile may be less related to the production of mesothelioma than other types of asbestos fibers.     

Mortality of glass filament (textile) workers

A historical prospective mortality study was conducted at a glass filament plant in Ontario, Canada. The cohort consisted of 1465 men and women who had worked for a total of at least one year between 1951 (when the operations began) and 1986. Ninety six deaths were found in the 96% of persons traced. Mortality was compared by the person-years method with that of the Ontario population. An estimate of cumulative dust exposure was made based on long term employees' recollections of past conditions. Overall mortality was below that expected (standardised mortality ratio (SMR) = 76) based on 82 deaths. There were 11 deaths due to lung cancer; slightly but not significantly more than expected (SMR = 136, p = 0.31). Analysis by both duration of employment and cumulative exposure showed this increase to be inconsistent with an occupational aetiology.     

Mortality of glass filament (textile) workers.

A historical prospective mortality study was conducted at a glass filament plant in Ontario, Canada. The cohort consisted of 1465 men and women who had worked for a total of at least one year between 1951 (when the operations began) and 1986. Ninety six deaths were found in the 96% of persons traced. Mortality was compared by the person-years method with that of the Ontario population. An estimate of cumulative dust exposure was made based on long term employees' recollections of past conditions. Overall mortality was below that expected (standardised mortality ratio (SMR) = 76) based on 82 deaths. There were 11 deaths due to lung cancer; slightly but not significantly more than expected (SMR = 136, p = 0.31). Analysis by both duration of employment and cumulative exposure showed this increase to be inconsistent with an occupational aetiology.     

A mortality study among workers in an English asbestos factory.

The previous report on this cohort study of workers in an asbestos textile factory (Knox et al., 1968) showed little evidence of increased mortality among workers who had entered the factory after the implementation in 1932 of the first Asbestos Industry Regulation (1931) but observed that no firm conclusions could be drawn, as little carcinogenic effect would be expected for 20 years after first exposure. A further 8 1/2 years of follow-up has revealed some asbestos-related disease in this latter group, although very much less than for employees first exposed before 1933. Among the 963 workers first exposed in 1933 or later, mortality was increased for carcinoma of the bronchus (31 deaths; 19-3 expected for all lung cancers) and non-malignant respiratory disease (35 deaths, 25-0 expected), and a further 5 deaths were attributed to pleural mesothelioma.     

Mortality among members of a heavy construction equipment operators union with potential exposure to diesel exhaust emissions

A historical prospective mortality study was conducted on a cohort of 34 156 male members of a heavy construction equipment operators union with potential exposure to diesel exhaust emissions. This cohort comprised all individuals who were members of the International Union of Operating Engineers, Locals 3 and 3A, for at least one year between 1 January 1964 and 31 December 1978. The mortality experience of the entire cohort and several subcohorts was compared with that of United States white men, adjusted for age and calendar time. The comparison statistic was the commonly used standardised mortality ratio (SMR). Historical environmental measurements did not exist, but partial work histories were available for some cohort members through the union dispatch computer tapes. An attempt was made to relate mortality experience to the union members' dispatch histories. Overall mortality for the entire cohort and several subgroups was significantly lower than expected. When cause specific mortality was examined, however, the study provided suggestive evidence for the existence of several potential health problems in this cohort. Mortality from liver cancer for the entire cohort was significantly high. Although mortality from lung cancer for the entire cohort was similar to expected, a positive trend by latency was observed for lung cancer. A significant excess of mortality from lung cancer was found among the retirees and the group for whom no dispatch histories were available. Other dispatch groups showed no evidence of lung cancer excess. In addition, the total cohort experienced significant mortality excess from emphysema and accidental deaths.     

Mortality among employees at a plastics and resins research and development facility.

OBJECTIVES--The study was undertaken to update a previous study of employees from a resins and plastics research and development facility and to further examine the mortality of these employees with particular emphasis on deaths due to pancreatic cancer. METHODS--This retrospective cohort study examined mortality from 1962 to 1992 for 257 men who were employed for at least one year during a 14 year period from 1962 to 1975 at a plastics and resins research and development facility. During the operative period, the primary activities involved applications and process development for polypropylene, polystyrene, epoxy resins, and to a lesser extent high density polyethylene. RESULTS--The cohort was young and was followed up for an average of 26 years. Although mortality for all causes among employees who worked at least one year at this facility was low (standardised mortality ratio (SMR) 0.74), the death rate from cancer was moderately higher than that of the general population (14 observed and 9.4 expected deaths). There were four observed and 0.5 expected deaths from pancreatic cancer among men who worked at this facility for at least one year, which resulted in a statistically increased SMR of 8.88 (95% confidence interval 2.42-22.74). All cases of pancreatic cancer had "laboratory" jobs, and their ages at death were relatively young compared with deaths in the general population from pancreatic cancer. Lung cancer mortality was high but not significant with seven observed and 3.5 expected deaths. There were no deaths due to non-malignant respiratory disease (1.9 expected). CONCLUSIONS--The increased cancer mortality was entirely due to excess deaths from pancreatic and lung cancers. No causative agent or process for these cases of pancreatic cancer has been identified. This study shows no increased colorectal cancer mortality as was found among another group of workers involved in the manufacture of polypropylene.     

Mortality among members of a heavy construction equipment operators union with potential exposure to diesel exhaust emissions.

A historical prospective mortality study was conducted on a cohort of 34 156 male members of a heavy construction equipment operators union with potential exposure to diesel exhaust emissions. This cohort comprised all individuals who were members of the International Union of Operating Engineers, Locals 3 and 3A, for at least one year between 1 January 1964 and 31 December 1978. The mortality experience of the entire cohort and several subcohorts was compared with that of United States white men, adjusted for age and calendar time. The comparison statistic was the commonly used standardised mortality ratio (SMR). Historical environmental measurements did not exist, but partial work histories were available for some cohort members through the union dispatch computer tapes. An attempt was made to relate mortality experience to the union members' dispatch histories. Overall mortality for the entire cohort and several subgroups was significantly lower than expected. When cause specific mortality was examined, however, the study provided suggestive evidence for the existence of several potential health problems in this cohort. Mortality from liver cancer for the entire cohort was significantly high. Although mortality from lung cancer for the entire cohort was similar to expected, a positive trend by latency was observed for lung cancer. A significant excess of mortality from lung cancer was found among the retirees and the group for whom no dispatch histories were available. Other dispatch groups showed no evidence of lung cancer excess. In addition, the total cohort experienced significant mortality excess from emphysema and accidental deaths.     

Twenty years' follow-up study of asbestos workers

This report describes a cohort study conducted on workers who were employed in a factory mainly manufacturing asbestos yarn and cloth and were followed from 1964 to 1981. A total of 208 workers (73 males and 135 females) could be traced and 15 deaths were observed by the end of 1983. Among them, three had lung cancer and its relative risk was 6.8 (p less than 0.05) computed based on the age, sex and year specific death rates of Osaka Prefecture. One case of peritoneal mesothelioma was also found. The period from first asbestos exposure to death of these four cases of asbestos-related malignancies was more than 25 yr. In the analysis of the employees who had more than 1 yr of exposure to asbestos and those who had already been engaged in this factory at the beginning of the observation, the relative risk of lung cancer was 8.1 and 13.6, respectively.     

Mortality of workers manufacturing friction materials using asbestos

A mortality (1942-80) study was carried out on 13460 workers of a factory producing friction materials. The only type of asbestos used was chrysotile, except during two well-defined periods before 1945 when crocidolite was used, and over 99% of the population was traced. Compared with national death rates there were no detectable excesses of deaths due to lung cancer, gastrointestinal cancer, or other cancers; 11 deaths were due to pleural mesothelioma. A case-control study was carried out on deaths due to mesothelioma; this showed that eight workers had been exposed to crocidolite and another was possibly exposed intermittently to crocidolite. The other two had been employed for most of their working lives outside the factory, and their mesotheliomas could not be definitely attributed to exposure to chrysotile. Limiting the study to cases and controls who had exposure to 5 fibres/ml of chrysotile asbestos it was found that five of the six cases compared with two of the 10 controls had also been exposed to crocidolite. The probability (1:36) of this occurring were there no association with crocidolite is most unlikely. A case-control study was also carried out on deaths due to lung cancer and gastrointestinal cancer to investigate the dose-response relationships between these tumours and exposure to chrysotile. Measured and estimated fibre concentrations were available for the different jobs over the period of the study. No dose-response relationships were observed, but the exposures were low with only 5% of men accumulating 100 fibre-years/ml. The experience at this factory over a 40-year period showed that chrysotile asbestos was processed with no detectable excess mortality.