Health of workmen in the chromate-producing industry in Britain.

In a follow-up study of 2715 men who had worked for at least one year at the three chromate-producing factories in Britain between 1948 and 1977 only 298 were lost to follow-up, and the average number of person-years in the study was 16.3. One hundred and sixteen deaths from lung cancer occurred in these men, with only 48.0 expected (O/E = 2.4; p less than 0.001). For men employed at the factory, which is still in operation, the relative risk of lung cancer has decreased from over 3.0 before plant modification to about 1.8 in those who have worked only since plant modification. A multivariate analysis was used in an attempt to unravel the overlapping influence of duration of employment, length of follow-up, plant modification, factory, age at entry to work, and estimated degree of chromate exposure. The major dependent factor appeared to be duration of employment; in addition the analysis suggested that modifications in the plant and work environment had been associated with an appreciable reduction of the excess risk from lung cancer.     

Exposures to silica mixed dust and cohort mortality study in tin mines: exposure-response analysis and risk assessment of lung cancer

BACKGROUND: Mineral dusts that contain crystalline silica have been associated directly or indirectly with the development of pneumoconiosis or silicosis, non-malignant respiratory diseases, lung cancer, and other diseases. The health impacts on workers with silica mixed dust exposure in tin mines and dose-response relationships between cumulative dust exposure and the mortality from lung cancer are investigated. METHODS: A cohort of 7,837 workers registered in the employment records in 4 Chinese tin mines between 1972 and 1974 was identified for this study and the mortality follow-up was traced through 1994. Of the cohort, the cause of death was ascertained for 1,061 (97%) of the 1,094 deceased workers. Standardized mortality ratios (SMRs) were calculated for all workers, non-exposed workers, and dust-exposed workers with different exposure levels, silicotics, and non-silicotics based on Chinese national rates. RESULTS: The mortality from all causes in four tin mines was nearly the same as the national mortality. Malignant neoplasm, cerebrovascular disease, and cardiovascular disease accounted for 68.6% of all deaths. Mortality excess from lung cancer, liver cancer, all malignant diseases, and non-malignant respiratory diseases was observed among dust-exposed workers; a 50-fold excess of pneumoconiosis was observed. There was an upward trend for SMRs of lung cancer was noted from no exposure to low, medium, and high exposure levels (SMRs=1.29, 2.65, 2.66, 3.33). The shape of the exposure-response curve for risk of lung cancer at high exposure levels was inconsistent in these four mines. CONCLUSIONS: The findings indicated a positive dose-response relation between exposure to cumulative dust and the mortality of lung cancer. High arsenic content in dust particles, together with crystalline silica, may play an important role in causing increased mortality from lung cancer.     

Lung cancer mortality among workers making lead chromate and zinc chromate pigments at three English factories

Lung cancer mortality among 1152 men working at three English chromate pigment factories was studied from the 1930s or 1940s until 1981. Workers at factory C were exposed only to lead chromate and experienced normal mortality (Obs/Exp deaths 7/6.45). Workers at factories A and B were exposed to both lead and zinc chromate; mortality was normal among those who had only low exposure (O/E 7/6.95). For workers with high or medium exposure lung cancer mortality was significantly raised among men remaining at least a year after entering service at factory A during 1932-54 (O/E 21/9.45) and at factory B during 1948-67 (O/E 11/2.50). At factory A, 1933-46 entrants staying only 3-11 months were not affected (O/E 6/5.04) and 1955-63 entrants also appeared unaffected (O/E 2/2.00); working conditions there improved in 1955. The hazard at factories A and B affected workers who left after one year as well as those with longer service, and latent intervals were unusually short. The results indicate that moderate or heavy exposure to zinc chromate may give rise to a severe risk of developing lung cancer, but that exposure which is relatively mild or lasts less than a year may not constitute an effective risk. The results provide no indication that lead chromate induces lung cancer in man, even under conditions conducive to lead poisoning.     

Lung cancer mortality among workers making lead chromate and zinc chromate pigments at three English factories.

Lung cancer mortality among 1152 men working at three English chromate pigment factories was studied from the 1930s or 1940s until 1981. Workers at factory C were exposed only to lead chromate and experienced normal mortality (Obs/Exp deaths 7/6.45). Workers at factories A and B were exposed to both lead and zinc chromate; mortality was normal among those who had only low exposure (O/E 7/6.95). For workers with high or medium exposure lung cancer mortality was significantly raised among men remaining at least a year after entering service at factory A during 1932-54 (O/E 21/9.45) and at factory B during 1948-67 (O/E 11/2.50). At factory A, 1933-46 entrants staying only 3-11 months were not affected (O/E 6/5.04) and 1955-63 entrants also appeared unaffected (O/E 2/2.00); working conditions there improved in 1955. The hazard at factories A and B affected workers who left after one year as well as those with longer service, and latent intervals were unusually short. The results indicate that moderate or heavy exposure to zinc chromate may give rise to a severe risk of developing lung cancer, but that exposure which is relatively mild or lasts less than a year may not constitute an effective risk. The results provide no indication that lead chromate induces lung cancer in man, even under conditions conducive to lead poisoning.     

A "lugged" analysis of lung cancer risks in UK carbon black production workers, 1951-2004

BACKGROUND: Previously published analyses of excess lung cancer risks in UK carbon black production workers attracted no confident interpretation. METHODS: The mortality of a cohort of 1,147 male manual workers from five UK factories manufacturing carbon black was investigated for the period 1951-2004. All subjects were first employed in the period 1947-74 and were employed for 12 months or more. Limited work histories were available to calculate estimates of individual cumulative exposure to carbon black. RESULTS: Based on serial rates for the general population of England and Wales, significantly elevated mortality was observed for lung cancer (Obs 67, SMR 146, P < 0.01) but not for all other causes combined (Obs 426, SMR 106). There was highly elevated lung cancer mortality at two of the plants (SMR 230, Obs 35) but no excess mortality at the other three plants combined (SMR 104, Obs 32). Analyses by period since leaving employment indicated elevated lung cancer risks were limited to those workers with some employment in the most recent 15 years. SMR analyses found an overall positive significant trend between lung cancer risks and cumulative carbon black exposure received in the most recent 15 years. Poisson regression analyses provided different results depending on which variables were adjusted for. CONCLUSIONS: The findings suggest that carbon black, or chemicals associated with the production of carbon black, had an effect on later stages of lung cancer carcinogenesis at two of the plants but that no such effect was found at the other plants.     

Mortality from respiratory cancer and other causes in United Kingdom chromate production workers.

This report updates a 1981 study of mortality at three United Kingdom chromate producing factories, and pays special attention to workers engaged after major plant and process changes were completed during 1958-60. The study covers 2298 payroll workers in post on 1 January 1950 or entering employment up to 30 June 1976 and remaining at least one year, with mortality observed up to 31 December 1988. Expected numbers of deaths were calculated from national death rates adjusted for social class and area differences. At the two largest factories 1422 men starting work before the process changes showed a highly significant excess of deaths from lung cancer (observed deaths/adjusted expected deaths (obs/expA) 175/88.97, adjusted standardised mortality ratio (SMRA) 197). They also had a significant excess of deaths from nasal cancer (obs/expA 4/0.26, SMRA 1538); the four affected men all had over 20 years of employment. Six hundred and seventy seven men starting work after the completion of process changes showed no excess of lung cancer deaths (obs/expA 14/13.7, SMRA 102, 95% confidence interval (95% CI) 56-171), but the possibility of the risk persisting at a reduced level cannot be excluded. The risk among earlier entrants affected men with two or more years of employment and was highest among those working for 10 years or longer (SMRA 225). The relative risk was already raised 5-14 years after first employment; it was highest in the 25-40 year period, but was still raised 50 years after first exposure. The risk showed most clearly at young ages, with a SMRA of 355 for ages under 50 (obs/expA 21/5.91). The excess was greater among men in jobs with high exposure to chromates (obs/expA 151/61.73, SMRA 245) than among men in less exposed jobs (obs/expA 21/19.57, SMRA 107). Less evidence of a lung cancer excess was found among 199 men employed at a third small factory (obs/expA 12/9.91, SMRA 121). No risk was apparent in further groups of 214 salaried works staff (obs/expA 1/2.53), or 95 workers at an adjacent fertiliser plant (obs/expA 3/3.95). No significant excesses of deaths from cancers of other sites were found.     

Mortality from respiratory cancer and other causes in United Kingdom chromate production workers

This report updates a 1981 study of mortality at three United Kingdom chromate producing factories, and pays special attention to workers engaged after major plant and process changes were completed during 1958-60. The study covers 2298 payroll workers in post on 1 January 1950 or entering employment up to 30 June 1976 and remaining at least one year, with mortality observed up to 31 December 1988. Expected numbers of deaths were calculated from national death rates adjusted for social class and area differences. At the two largest factories 1422 men starting work before the process changes showed a highly significant excess of deaths from lung cancer (observed deaths/adjusted expected deaths (obs/expA) 175/88.97, adjusted standardised mortality ratio (SMRA) 197). They also had a significant excess of deaths from nasal cancer (obs/expA 4/0.26, SMRA 1538); the four affected men all had over 20 years of employment. Six hundred and seventy seven men starting work after the completion of process changes showed no excess of lung cancer deaths (obs/expA 14/13.7, SMRA 102, 95% confidence interval (95% CI) 56-171), but the possibility of the risk persisting at a reduced level cannot be excluded. The risk among earlier entrants affected men with two or more years of employment and was highest among those working for 10 years or longer (SMRA 225). The relative risk was already raised 5-14 years after first employment; it was highest in the 25-40 year period, but was still raised 50 years after first exposure. The risk showed most clearly at young ages, with a SMRA of 355 for ages under 50 (obs/expA 21/5.91). The excess was greater among men in jobs with high exposure to chromates (obs/expA 151/61.73, SMRA 245) than among men in less exposed jobs (obs/expA 21/19.57, SMRA 107). Less evidence of a lung cancer excess was found among 199 men employed at a third small factory (obs/expA 12/9.91, SMRA 121). No risk was apparent in further groups of 214 salaried works staff (obs/expA 1/2.53), or 95 workers at an adjacent fertiliser plant (obs/expA 3/3.95). No significant excesses of deaths from cancers of other sites were found.     

A Study of the mortality of female asbestos workers

Newhouse, M. L., Berry, G., Wagner, J. C., and Turok, M. E. (1972).Brit. J. industr. Med.,29, 134-141. A study of the mortality of female asbestos workers. A cohort study of over 900 women employed at an asbestos factory making both textiles and insulation materials is described. It extends the information about asbestos-related disease at this factory which was previously available only for male workers. The cohort was defined as all the women who started employment at the factory between 1936 and 1942 and the main analysis was of mortality up to the end of 1968. This analysis was made in relation to job, length of exposure, and age at first exposure. Compared with national rates there was excess overall mortality among those who worked in jobs with low to moderate exposure partly accounted for by deaths from cancer. In the group with severe exposure, who had worked in the factory for less than two years, there was an excess of cancer of the lung and pleura. However, the most marked increased mortality was in those with severe exposure who had worked for more than two years in the factory; in this group there were excess deaths from cancer of the lung and pleura, from other cancers, and from respiratory diseases. There were no significant trends of excess mortality with age at first exposure. The smoking habits of some of the deceased women were obtained and the indications were that the proportion of smokers in the cohort was higher than the national rate. This could account for some of the excess mortality but the trend of this excess with exposure indicated the role of asbestos. Necropsy reports and/or histological material were obtained for 43% of those who had died. Three deaths registered as cancer of the pleura were identified as pleural mesothelial tumours; in all there were 11 mesotheliomas, six of pleural and five of peritoneal origin.     

Lung cancer among workers in chromium chemical production

BACKGROUND: An elevated risk of lung cancer among workers in chromate production facilities has previously been reported. This excess risk is believed to be the result of exposure to hexavalent chromium. There have been mixed reports about whether trivalent chromium exposure is also associated with an excess lung cancer risk. Previous studies of measured hexavalent chromium exposure and lung cancer risk have not examined cigarette smoking as a risk factor. METHODS: A cohort of 2,357 workers first employed between 1950 and 1974 at a chromate production plant was identified. Vital status of the workers was followed until December 31, 1992. Work histories of cohort members were compiled from the beginning of employment through 1985, the year the plant closed. Annual average exposure estimates, based on historical exposure measurements, were made for each job title in the plant for the years 1950-1985. These exposure estimates were used to calculate the cumulative hexavalent chromium exposure of each member of the study population. Following closure of the plant, settled dust samples were collected and analyzed for hexavalent and trivalent chromium. The trivalent/hexavalent concentration ratios in each plant area were combined with historic air-sampling data to estimate cumulative trivalent chromium exposure for each individual in the study cohort. Smoking status (yes/no) as of the beginning of employment and clinical signs of potential chromium irritation were identified from company records. RESULTS: Cumulative hexavalent chromium exposure showed a strong dose-response relationship for lung cancer. Clinical signs of irritation, cumulative trivalent chromium exposure, and duration of work were not found to be associated with a risk of lung cancer when included in a proportional hazards model with cumulative hexavalent chromium exposure and smoking. Age-specific data on cumulative hexavalent chromium exposure, observed and expected numbers of lung cancer cases, and person-years of observation are provided. CONCLUSIONS: Cumulative hexavalent chromium exposure was associated with an increased lung cancer risk; cumulative trivalent chromium exposure was not. The excess risk of lung cancer associated with cumulative hexavalent chromium exposure was not confounded by smoking status. The current study offers the best quantitative evidence to date of the relationship between hexavalent chromium exposure and lung cancer. Am. J. Ind. Med. 38:115-126, 2000. Published 2000 Wiley-Liss, Inc.     

Mortality among aircraft manufacturing workers

OBJECTIVES: To evaluate the risk of cancer and other diseases among workers engaged in aircraft manufacturing and potentially exposed to compounds containing chromate, trichloroethylene (TCE), perchloroethylene (PCE), and mixed solvents. METHODS: A retrospective cohort mortality study was conducted of workers employed for at least 1 year at a large aircraft manufacturing facility in California on or after 1 January 1960. The mortality experience of these workers was determined by examination of national, state, and company records to the end of 1996. Standardised mortality ratios (SMRs) were evaluated comparing the observed numbers of deaths among workers with those expected in the general population adjusting for age, sex, race, and calendar year. The SMRs for 40 cause of death categories were computed for the total cohort and for subgroups defined by sex, race, position in the factory, work duration, year of first employment, latency, and broad occupational groups. Factory job titles were classified as to likely use of chemicals, and internal Poisson regression analyses were used to compute mortality risk ratios for categories of years of exposure to chromate, TCE, PCE, and mixed solvents, with unexposed factory workers serving as referents. RESULTS: The study cohort comprised 77,965 workers who accrued nearly 1.9 million person-years of follow up (mean 24.2 years). Mortality follow up, estimated as 99% complete, showed that 20,236 workers had died by 31 December 1996, with cause of death obtained for 98%. Workers experienced low overall mortality (all causes of death SMR 0.83) and low cancer mortality (SMR 0.90). No significant increases in risk were found for any of the 40 specific cause of death categories, whereas for several causes the numbers of deaths were significantly below expectation. Analyses by occupational group and specific job titles showed no remarkable mortality patterns. Factory workers estimated to have been routinely exposed to chromate were not at increased risk of total cancer (SMR 0.93) or of lung cancer (SMR 1.02). Workers routinely exposed to TCE, PCE, or a mixture of solvents also were not at increased risk of total cancer (SMRs 0.86, 1.07, and 0.89, respectively), and the numbers of deaths for specific cancer sites were close to expected values. Slight to moderately increased rates of non-Hodgkin''s lymphoma were found among workers exposed to TCE or PCE, but none was significant. A significant increase in testicular cancer was found among those with exposure to mixed solvents, but the excess was based on only six deaths and could not be linked to any particular solvent or job activity. Internal cohort analyses showed no significant trends of increased risk for any cancer with increasing years of exposure to chromate or solvents. CONCLUSIONS: The results from this large scale cohort study of workers followed up for over 3 decades provide no clear evidence that occupational exposures at the aircraft manufacturing factory resulted in increases in the risk of death from cancer or other diseases. Our findings support previous studies of aircraft workers in which cancer risks were generally at or below expected levels.       

Diesel exhaust exposure and mortality among males in the American Cancer Society prospective study

In 1982, the American Cancer Society enrolled over 1.2 million American men and women in a prospective mortality study of cancer and other causes in relation to different risk factors. The 2-year mortality of 461,981 males aged 40-79 years with known smoking habit has been analyzed in relation to exposure to diesel exhaust (DE) and to employment in selected occupations related to DE exposure. The relative risk (RR) for all causes of death for those exposed was 1.05 (95% confidence interval [CI]: 0.97-1.13). For lung cancer, the RR was 1.18 (95% CI: 0.97-1.44). A dose-response effect was present. Railroad workers, heavy equipment operators, miners, and truck drivers had a higher mortality both for all causes and for lung cancer when compared with subjects with other occupations and no exposure to DE. Truck drivers exposed to DE were not at excess risk of lung cancer if compared with truck drivers unexposed to DE, but a trend of increasing risk with duration of exposure was suggested. DE exposure was also associated with increase in mortality for accidents, cerebrovascular disease, arteriosclerosis, and cirrhosis of the liver. An association based on small numbers was also present for Hodgkin's disease and lymphoid leukemia. No association with chronic non-neoplastic pulmonary diseases or with bladder cancer was found.     

A case-control study of employment experience and lung cancer among rubber workers

In this case-control study the detailed employment histories of 121 rubber plant employees who died of lung cancer from 1964 through 1973 were compared to those of 448 plant employees (controls) who died of other causes during the same calendar period. All subjects were white male hourly employees. Lung cancer cases and controls were matched individually on year of birth and year of first hire at the plant. Results of matched analyses indicated that there was no association between lung cancer mortality and employment in either rubber compounding and mixing jobs or curing jobs. Men who had worked for at least five years in rubber reclaim operations, where there was potentially heavy exposure to particulates and fumes, experienced a twofold increase in lung cancer risk. In addition, there was a 70% excess of lung cancer risk among men employed in making special products, where the primary production activity was fuel cell manufacturing. The latter two findings were marginally statistically significant.     

A case-control study of lung cancer among refinery workers

This case-control study examined the relationship between lung cancer and the work histories of male employees at a large Texas refinery. The study included 112 lung cancer deaths observed between 1946 and 1987 and 490 matched controls. Employment histories were obtained from personnel records, and smoking information was available from medical records. Both stratification methods and conditional logistic regression were used in data analyses. Overall employment in four general job categories (administrative, engineering/laboratory, process, maintenance/mechanical) was not associated with lung cancer mortality. Results by hire period (< 1940, 1940+) showed that workers hired into process jobs before 1940 had a nonsignificantly elevated odds ratio (OR) of 1.71 (95% confidence interval [CI] = 0.85-3.45) compared with nonprocess workers hired before 1940. Among process workers hired before 1940, there was a significant trend toward increasing OR with increasing duration of employment in process jobs, and the association with lung cancer was strongest among smokers in the highest duration category of 30+ years (OR = 2.98, 95% CI = 1.07-8.31). Latency analyses of process workers hired before 1940 indicated that their lung cancer risk had peaked between 30 and 50 years since first employment. Definitive statements about causal factors are limited because results among process workers were based on small numbers of subjects in some exposure categories, and there was no information on specific workplace exposures. The OR for maintenance/mechanical jobs after adjustment for smoking was 1.00 (95% CI = 0.55-1.82). Furthermore, there was no pattern in relation to duration of employment in maintenance/mechanical jobs. The results from this study do not support the hypothesis that work in maintenance/mechanical jobs increases lung cancer risk. On the basis of analyses in this study, it is unlikely that asbestos exposure contributed to excess lung cancer mortality. Additional analyses were conducted for specific maintenance jobs with potential exposure to asbestos and by duration in jobs with occasional or routine asbestos exposure. No significant increase in lung cancer was found in any subgroup. Furthermore, there was no significant trend toward lung cancer risk in relation to duration of employment in jobs with asbestos exposure.     

Study of two cohorts of workers exposed to methyl methacrylate in acrylic sheet production

OBJECTIVES—To study mortality among 4324 workers at two United Kingdom factories, Darwen, Lancashire and Wilton, Cleveland, producing polymethyl methacrylate (PMMA) sheet. The Darwen factory is still active, but the Wilton one was closed in 1970. Also, to investigate patterns of mortality after exposure to methyl methacrylate; in particular, mortality from colon and rectal cancer.
METHODS—All male employees at the Darwen factory with a record of employment in 1949-88 and all men ever employed at the Wilton factory (1949-70) were investigated. The vital status of both cohorts was ascertained on 31 December 1995. The exposure of 1526 subjects at the Darwen plant who were engaged from 1949 onwards could be characterised. The mean duration of exposure was 7.6 years at 13.2 ppm (8 hour time weighted average), although exposures in some work groups were as high as 100 ppm. It was not possible to calculate the cumulative exposure of workers first employed at the Darwen plant before 1949 or workers at the Wilton factory.
RESULTS—In the Darwen cohort, 622 deaths were identified and a further 700 deaths in the Wilton cohort. Mortalities for the cohort were compared with national and local rates and expressed as standardised mortality ratios (SMRs). In the subcohort of Darwen workers with more than minimal exposure to MMA, reduced mortalities compared with national and local rates, were found for all causes (SMR 94), and colorectal cancer (SMR 92), but mortality from all cancers was slightly increased (SMR 104). No relations were found with cumulative exposure to MMA. In the subcohort of Wilton workers, mortality from all causes of death was significantly reduced (SMR 89), but mortality from all cancers (SMR 103) and colorectal cancer (SMR 124) were increased. The excess of colorectal cancer was confined to employees with less than 1 year of employment.
CONCLUSION—The study provided no clear evidence that employment at the factories or exposure to MMA had adversely affected the mortalities of workers.


Keywords: methyl methacrylate; mortality     

Lung cancer in a non-ferrous smelter: the role of cadmium

Lung cancer mortality was examined in a cohort of 4393 men employed at a zinc-lead-cadmium smelter. There was an excess of lung cancer (overall SMR = 124.5, 95% confidence interval 107-144) which was particularly evident for those employed for more than 20 years. A statistically significant trend in SMRs with increasing duration of employment was apparent. Quantitative estimates of exposure to cadmium and ordinal rankings for lead, arsenic, zinc, sulphur dioxide, and dust were used to calculate cumulative exposures from job histories. Matched logistic regression was used to compare the cumulative exposures of cases of lung cancer to those of controls matched for date of birth and date of starting work and surviving at the time of death of the matched cases. The increasing risk of lung cancer associated with increasing duration of employment could not be accounted for by cadmium and did not appear to be restricted to any particular process or department. Although lung cancer mortality was associated with estimates of cumulative exposure to arsenic and to lead, it was not possible to determine whether the increased risk might be due to arsenic, lead, or to other contaminants in the smelter. These results are compared with findings from other non-ferrous smelters.     

Lung cancer in a non-ferrous smelter: the role of cadmium.

Lung cancer mortality was examined in a cohort of 4393 men employed at a zinc-lead-cadmium smelter. There was an excess of lung cancer (overall SMR = 124.5, 95% confidence interval 107-144) which was particularly evident for those employed for more than 20 years. A statistically significant trend in SMRs with increasing duration of employment was apparent. Quantitative estimates of exposure to cadmium and ordinal rankings for lead, arsenic, zinc, sulphur dioxide, and dust were used to calculate cumulative exposures from job histories. Matched logistic regression was used to compare the cumulative exposures of cases of lung cancer to those of controls matched for date of birth and date of starting work and surviving at the time of death of the matched cases. The increasing risk of lung cancer associated with increasing duration of employment could not be accounted for by cadmium and did not appear to be restricted to any particular process or department. Although lung cancer mortality was associated with estimates of cumulative exposure to arsenic and to lead, it was not possible to determine whether the increased risk might be due to arsenic, lead, or to other contaminants in the smelter. These results are compared with findings from other non-ferrous smelters.     

Follow up study of workers manufacturing chrysotile asbestos cement products.

A cohort study has been carried out of 2167 subjects employed between 1941 and 1983 at an asbestos cement factory in England. The production process incorporated the use of chrysotile asbestos fibre only, except for a small amount of amosite during four months in 1976. Measured airborne fibre concentrations available since 1970 from personal samplers showed mean levels below 1 fibre/ml, although higher levels had probably occurred previously in certain areas of the factory. No excess of lung cancer was observed in the mortality follow up by comparison with either national or local death rates, and analyses of subgroups of the workforce by job, exposure level, duration of employment, duration since entry, or calendar years of employment gave no real suggestion of an asbestos related excess for this cause of death. There was one death from pleural mesothelioma and one with asbestosis mentioned as an associated cause on the death certificate, but neither is thought to be linked to asbestos exposure at this factory. Other suggested asbestos related cancers, such as laryngeal and gastrointestinal, did not show raised risks. Although the durations of exposure were short in this study, the findings are consistent with two other studies of workers exposed to low concentrations of chrysotile fibre in the manufacture of asbestos cement products which reported no excess mortality.     

Follow up study of workers manufacturing chrysotile asbestos cement products

A cohort study has been carried out of 2167 subjects employed between 1941 and 1983 at an asbestos cement factory in England. The production process incorporated the use of chrysotile asbestos fibre only, except for a small amount of amosite during four months in 1976. Measured airborne fibre concentrations available since 1970 from personal samplers showed mean levels below 1 fibre/ml, although higher levels had probably occurred previously in certain areas of the factory. No excess of lung cancer was observed in the mortality follow up by comparison with either national or local death rates, and analyses of subgroups of the workforce by job, exposure level, duration of employment, duration since entry, or calendar years of employment gave no real suggestion of an asbestos related excess for this cause of death. There was one death from pleural mesothelioma and one with asbestosis mentioned as an associated cause on the death certificate, but neither is thought to be linked to asbestos exposure at this factory. Other suggested asbestos related cancers, such as laryngeal and gastrointestinal, did not show raised risks. Although the durations of exposure were short in this study, the findings are consistent with two other studies of workers exposed to low concentrations of chrysotile fibre in the manufacture of asbestos cement products which reported no excess mortality.     

Dust exposure and mortality in chrysotile mining, 1910-75.

We report a further follow-up of a birth cohort of 11 379 workers exposed to chrysotile. The cohort consisted of 10 939 men and 440 women, born 1891-1920, who had worked for at least a month in the mines and mills of Asbestos and Thetford Mines in Quebec. For all subjects, length of service and estimates of accumulated dust exposure were obtained, with a smoking history for the vast majority. Three methods of analysis, two based on the "man-years" methods, the other a "case-and-multiple-controls" approach, gave results consistent with one another and with previous analyses. By the end of 1975, 4463 men and 84 women had died. Among men, the overall excess mortality, 1926-75 was 2% at Asbestos and 10% at Thetford Mines, much the dustier region. The women, mostly employed at Asbestos, had a standardised mortality ratio (SMR) all causes, 1936-75) of 0.90. Analysis of deaths 20 years or more after first employment showed that in men with short service (less than five years) there was no discernible correlation with dust exposure. Among men employed at least 20 years, there were clear excesses in those exposed to the heaviest dust concentrations. Reanalysis in terms of exposure to age 45 showed definite and consistent trends for SMRs for total mortality, for lung cancer, and for pneumoconiosis to be higher the heavier the exposure. The response to increasing dose was effectively linear for lung cancer and for pneumoconiosis. Lung cancer deaths occurred in non-smokers, and showed a greater increase of incidence with increasing exposure than did lung cancer in smokers, but there was insufficient evidence to distinguish between multiplicative and additive risk models. There were no excess deaths from laryngeal cancer, but a clear association with smoking. Ten men and one woman died from pleural mesothelioma. If the only subjects studied had been the 1904 men with at least 20 years' employment in the lower dust concentrations, averaging 6.6 million particles per cubic foot (or about 20 fibres/cc), excess mortality would not have been considered statistically significant, except for pneumoconiosis. The inability of such a large epidemiological survey to detect increased risk at what, today, are considered unacceptable dust concentrations, and the consequent importance of exposure-response models are therefore emphasised.     

Lung cancer mortality among workers in the European production of man-made mineral fibers--a Poisson regression analysis.

One hundred and eighty-one lung cancer deaths among workers during 301,085 person-years in European man-made mineral fiber production between 1930-1955 and 1982 were analyzed according to Poisson regression models including age, calendar period, country, and exposure variables. Time since first employment was the variable most strongly associated with lung cancer risk in both the rock-slag wool and glass wool subcohorts. Workers in the early technological phase were at higher risk than those in other categories, particularly in rock-slag wool production. No clear trend with duration of employment was suggested. No major changes occurred in the interpretation of the results when workers with less than one year of employment or less than 20 years since first exposure were excluded. The original results, based on analyses for standardized mortality ratios, were confirmed, and workers with a short duration of employment or a short time since first employment did not need to be excluded from the analysis.