A cohort mortality and nested case-control study of French and Austrian talc workers

Objectives: To study whether the mortality from non-malignant and malignant respiratory diseases of workers employed in French and Austrian talc mines and mills is related to their long term occupational exposure.     

An updated cohort mortality study of workers at a northeastern United States petroleum refinery

An update of a cohort study of 4855 employees at a Paulsboro, New Jersey refinery was conducted to further examine mortality patterns. The earlier study investigated refinery workers employed for a minimum of 1 year between 1 January 1946 and 1 January 1979. The vital status of these workers was ascertained through 1979. The update extended enrollment in the study and vital status follow-up for an additional 8 years (1980–1987). As in the previous study, mortality from all causes [standardized mortality ratio (SMR) = 87; 95% confidence interval (95% CI): 83–91] was significantly lower than expected compared with the general population. Total cancer mortality was also lower than expected (SMR = 96; 95% CI: 86–106). A borderline significant mortality increase in prostatic cancer was found (SMR = 144; 95% CI: 106–190). This increase was similar to the nonsignificant increase reported in the original study (SMR = 135; 95% CI: 90–196). The excess was of comparable magnitude among white males and nonwhite males, although it was not significant for the latter. Detailed analysis indicated that the prostatic cancer was not likely to be related to employment at the refinery. Mortality from lymphatic and hematopoietic cancers was similar to the expected mortality. Mortality from overall leukemia was as expected and detailed analyses by specific cell type showed no increase. An increase in mortality occurred from non-Hodgkin's lymphoma among male workers (SMR = 132; 95% CI: 74–217). The increase was not statistically significant and unlikely to be associated with refinery employment. Mortality from multiple myeloma among male employees was lower than expected (SMR = 74; 95% CI: 20–190). Mortality from asbestos-related diseases (pulmonary fibrosis, lung cancer, malignant mesothelioma) was also lower than expected among male workers. No cause-specific mortality was found to be associated with duration of employment at the refinery, including several causes which have been reported to be elevated in previous studies. The findings of this updated study indicate, as in the previous report, the generally favorable mortality experience of Paulsboro refinery workers.The work for this study was performed at Mobil Corporate Medical Department     

A cohort mortality study and a case-control study of workers potentially exposed to styrene in the reinforced plastics and composites industry

The cohort consisted of 15,908 men and women who worked for at least six months between 1948 and 1977 in 30 participating manufacturing plants in the reinforced plastics and composites industry. These workers were occupationally exposed to the working environment in the industry, which included exposure to styrene. Cause specific mortality analyses were performed based on the standardised mortality ratio (SMR) with the United States population as a comparison. No significant excess of cause specific mortality was found for the total cohort. Mortality from cancer was slightly less than expected (SMR = 88.1). For cancer of the respiratory system, a small non-significant excess was detected (SMR = 116.1). For lymphatic and haematopoietic cancer, a non-significant deficit was found (SMR = 73.3). The observed mortality from leukaemia was similar to that expected (five observed v 4.76 expected deaths). The plants with hot processes (injection moulding, centrifugal casting, compression moulding, continuous lamination, and pultrusion) experienced a significantly increased SMR (177.9) for respiratory cancer, which was more than twice that (78.3) for those with cold processes (resin mixing, lay up and spray up, bag moulding, and filament winding). As potential exposure to styrene from hot processes is considerably less than that from the cold processes, this finding could not be attributed to occupational exposures. A subsequent nested case-control study consisting of 40 cases of deaths from respiratory cancer was conducted. Further information on detailed work history, occupational exposures, and smoking history was collected. The case-control study did not show any significant association between respiratory cancer and direct exposure to styrene (contained in polyester resins), duration of exposure to styrene, the type of process (hot or cold), or whether a resin was used. A statistically significant association (relative risk = 7.33) was found between cigarette smoking and respiratory cancer among the study subjects.     

A cohort mortality study among titanium dioxide manufacturing workers in the United States.

Although titanium dioxide (TiO2) is generally regarded as a nontoxic mild pulmonary irritant, some laboratory studies have reported lung adenomas in rats exposed to high levels of TiO2. Limited data on health effects among humans exist. A retrospective cohort mortality study was conducted among 4241 TiO2 workers who were employed for at least 6 months, on or after January 1, 1960, at four TiO2 plants in the United States. Exposure categories, defined by plant, job title, and calendar years in the job, were created to examine mortality patterns in those jobs where the potential for TiO2 exposure is greatest. Standardized mortality ratios (SMRs) and their 95% confidence intervals (CI) were calculated to compare the mortality pattern of the workers with the general background population. Relative risks were estimated and trend tests were conducted to examine risk of disease among different exposure level groups in internal analyses. Workers experienced a significantly low overall mortality (SMR = 0.8; 95% CI = 0.8-0.9). No significantly increased SMRs were found for any specific cause of death. Deaths from lung cancer were as expected, and SMRs for this cancer did not increase with increasing TiO2 levels. Workers in jobs with greatest TiO2 exposure had significantly fewer than expected total deaths (SMR = 0.7; 95% CI = 0.6-0.9). Internal analyses revealed no significant trends or exposure-risk associations for total cancers, lung cancer, or other causes of death. Results from our study indicate that the exposures at these United States plants are not associated with increases in the risk of death from cancer or other diseases. Moreover, workers with likely higher levels of TiO2 exposure had similar mortality patterns to those with less exposure, as internal analyses among workers revealed no increase in mortality by level of TiO2 exposure.     

A cohort mortality study and a case-control study of workers potentially exposed to styrene in the reinforced plastics and composites industry.

The cohort consisted of 15,908 men and women who worked for at least six months between 1948 and 1977 in 30 participating manufacturing plants in the reinforced plastics and composites industry. These workers were occupationally exposed to the working environment in the industry, which included exposure to styrene. Cause specific mortality analyses were performed based on the standardised mortality ratio (SMR) with the United States population as a comparison. No significant excess of cause specific mortality was found for the total cohort. Mortality from cancer was slightly less than expected (SMR = 88.1). For cancer of the respiratory system, a small non-significant excess was detected (SMR = 116.1). For lymphatic and haematopoietic cancer, a non-significant deficit was found (SMR = 73.3). The observed mortality from leukaemia was similar to that expected (five observed v 4.76 expected deaths). The plants with hot processes (injection moulding, centrifugal casting, compression moulding, continuous lamination, and pultrusion) experienced a significantly increased SMR (177.9) for respiratory cancer, which was more than twice that (78.3) for those with cold processes (resin mixing, lay up and spray up, bag moulding, and filament winding). As potential exposure to styrene from hot processes is considerably less than that from the cold processes, this finding could not be attributed to occupational exposures. A subsequent nested case-control study consisting of 40 cases of deaths from respiratory cancer was conducted. Further information on detailed work history, occupational exposures, and smoking history was collected. The case-control study did not show any significant association between respiratory cancer and direct exposure to styrene (contained in polyester resins), duration of exposure to styrene, the type of process (hot or cold), or whether a resin was used. A statistically significant association (relative risk = 7.33) was found between cigarette smoking and respiratory cancer among the study subjects.     

Retrospective cohort mortality study of cancer among sewage plant workers

There is little known about the incidence of cancer among sewage workers. In this paper we examine findings from a retrospective cohort study of 487 white male sewer authority workers employed between January 1950 and October 1979. Vital status was ascertained for 93% of the cohort yielding a total of 6,886 person years. Total mortality from all causes was comparable to that of the general white male U.S. population (Standardized Mortality Ratio [SMR] = 0.91, 95% Confidence Interval [CI] = 0.77-1.07). The cohort was subdivided into those not exposed, and sewer workers who were exposed to sewage effluent, sludge, or wastewater containing chemicals including potential carcinogens. Among the nonexposed group, mortality from all causes was significantly low (SMR = 0.55, 95% CI = 0.33-0.88). Among the exposed sewer workers, mortality from all causes was not significantly different from that of the general white male U.S. population (SMR = 1.00, 95% CI = 0.84-1.19). Mortality from all cancers among exposed sewer workers was slightly higher than that of the general population (SMR = 1.19, 95% CI = 0.79-1.7). Statistically significant elevated mortality ratios were seen for cancer of the larynx (SMR = 7.93, 95% CI = 1.59-23.96), and cancer of the liver (SMR = 5.4, 95% CI = 1.10-16.05). Careful study of the medical and occupational histories of these cases suggested that larynx cancer was possibly work-related, while liver cancer was not. A group estimated to be the highest exposed, composed predominantly of operatives, had a higher directly adjusted death rate from all malignant neoplasms combined compared to all other workers (rate ratio = 1.64). These findings of increased risk of cancer among exposed sewage workers, especially operators, are based on small number of cases and should be interpreted with caution. Studies of larger cohorts are needed to clarify the risk of these cancers among sewage workers.     

Retrospective mortality cohort study of Italian workers compensated for silicosis

Objectives

To estimate cause specific mortality in a large cohort of Italian workers compensated for silicosis.

Methods

The cohort included 14 929 subjects (14 098 men and 831 women) compensated for silicosis between 1946 and 1979, alive on 1 January 1980, and resident in Tuscany (a region of central Italy with 3 547 000 inhabitants). Mortality follow up ranged from 1980 to 1999. Vital status and the causes of death were determined by linkage with the regional mortality registry and with the national mortality database. The cohort mortality rates were compared to the rates of the local reference population. SMRs and their 95% confidence intervals were computed assuming a Poisson distribution of the observed deaths. Specific SMR analyses were performed according to the level of disability, the year of compensation assignment, and the job type.

Results

A significant excess mortality was observed in male silicotics for cancer of the lung, trachea, and bronchus and cancer of the liver, respiratory diseases (silicosis, asbestosis, antracosilicosis, and other pneumoconiosis), and for tubercolosis. Statistically significant mortality excess was observed in female silicotics for respiratory diseases (specifically silicosis and other pneumoconiosis) and tuberculosis. Analyses for period of compensation assignment showed a twofold increased SMR for biliary tract cancer among female workers and for liver cancer among male workers compensated before 1970.

Conclusions

The excess mortality from respiratory tract cancers and respiratory tract diseases detected in Italian compensated silicotics are in agreement with previous epidemiological studies. Although the twofold increased risk for liver cancer among males is suggestive of a possible association with silica dust exposure, the finding needs to be confirmed.     

A retrospective cohort mortality study of workers exposed to formaldehyde in the garment industry

In order to assess the possible human carcinogenicity of formaldehyde we conducted a retrospective cohort mortality study of workers exposed for at least three months to formaldehyde in three garment facilities which produced permanent press garments. A total of 11,030 workers contributing 188,025 person-years were included in the study. Vital status was successfully ascertained through 1982 for over 96% of the cohort. The average (TWA) formaldehyde exposure at the three plants monitored in 1981 and 1984 by NIOSH was 0.15 ppm but past exposures may have been substantially higher. In general, mortality from nonmalignant causes was less than expected. A statistically significant excess in mortality from cancers of the buccal cavity (SMR = 343) and connective tissue (SMR = 364) was observed. Statistically nonsignificant excesses in mortality were observed for cancers of the trachea, bronchus and lung (SMR = 114), pharynx (SMR = 112), bladder (SMR = 145), leukemia and aleukemia (SMR = 113), and other lymphopoietic neoplasms (SMR = 170). Mortality from cancers of the trachea, bronchus and lung was inversely related to duration of exposure and latency. In contrast, mortality from cancers of the buccal cavity, leukemias, and other lymphopoietic neoplasms increased with duration of formaldehyde exposure and/or latency. These neoplasms also were found to be highest among workers first exposed during a time period of high potential formaldehyde exposures in this industry (1955-1962). However, it should be recognized that these findings are based on relatively small numbers and that confounding by other factors may still exist. The results from this investigation, although far from conclusive, do provide evidence of a possible relationship between formaldehyde exposure and the development of upper respiratory cancers (buccal), leukemias, and other lymphopoietic neoplasms in humans.     

A cohort mortality study of forestry workers exposed to phenoxy acid herbicides

A cohort mortality study was undertaken of forestry workers at a public electrical utility who had worked for six months or more during 1950-82 and who were routinely exposed to herbicides including phenoxy acids. A total of 1222 men with 25 274 years at risk experienced 80 deaths. Ascertainment of vital state at the end of follow up was 95.5%. The male population of the province (Ontario) was used as the reference group. Overall, no excess mortality was found in this cohort relative to the reference population. A statistically significant increase in deaths occurred, however, due to suicide (SMR = 210, 95% confidence interval, 95% CI 105-376) for the cohort as a whole. No deaths were seen due to cancers such as soft tissue sarcoma and non-Hodgkin's lymphoma that have been cited by other authors as being associated with exposure to phenoxy acid herbicides. Although the cohort is not large, the absence of deaths due to these cancers is consistent with findings from other studies with sufficient numbers to allow examination of specific risks. The cohort is still young, however, and at the end of follow up most had not reached an age when increased incidence of cancer would normally be expected.     

A cohort mortality study of workers exposed to chlorinated organic solvents in Taiwan

PURPOSE: A retrospective cohort mortality study based on standardized mortality ratios (SMRs) was conducted to investigate the possible association between exposure to chlorinated organic solvents and various types of cancer deaths. METHODS: Vital status and causes of death of study subjects were determined from January 1, 1985 to December 31, 1997 by linking cohort data with the National Mortality Database. Person-year accumulation began on the date of entry to the cohort, or January 1, 1985 (whichever came later), and ended on the closing date of the study (December 31, 1997), if alive; or the date of death. RESULTS: This retrospective cohort study examined cancer mortality among 86,868 workers at an electronics factory in the northern Taiwan. Using various durations of employment and latency and adjusting for age and calendar year, no significantly elevated SMR was found for any cancer in either male or female exposed workers when compared with the general Taiwanese population. In particular, the risk of female breast cancer was not found to be increased. Although ovarian cancer suggested an upward trend when analyzed by length of employment, ovarian cancer risk for the entire female cohort was not elevated. CONCLUSIONS: It is concluded that this study provided no evidence that exposure to chlorinated organic solvents was associated with human cancer risk.     

An updated mortality study of workers in three major United States refineries and chemical plants.

A historical cohort study of refinery and chemical plant workers, originally observed from 1970 to 1977, was updated to the end of 1982. This cohort included 25,321 active, retired, and terminated workers at the Exxon refineries and chemical plants in Baton Rouge, Louisiana; Baytown, Texas; and Bayway/Bayonne, New Jersey. An emphasis was placed on the cancers previously reported to be increased in at least one petrochemical worker population. The population included a high proportion of retirees, providing adequate work experience and latency to evaluate risks associated with employment. Vital status was determined for 98.3% of the population and death certificates were obtained for 99.9% of the decedents. Mortality for "all causes of death" (standardised mortality ratio (SMR) = 89, 95% confidence interval (95% CI) 87-91) and for "all cancers" (SMR = 94, 95% CI 89-100) were lower than expected based on state rates. History of cigarette smoking collected from individual medical records and summarised work histories were used for subgroup analyses. There was no indication that cancers of primary interest were increased; however, blue collar workers at one plant had raised rates of kidney cancer (SMR = 246, 95% CI 146-390), which may require further evaluation.     

A nested case-control study of lung cancer among silica exposed workers in China.

In an attempt to assess whether silica induces lung cancer, a nested case-control study of 316 male lung cancer cases and 1352 controls was carried out among pottery workers and tungsten, copper-iron, and tin miners from five provinces in south central China. Exposure to dust and silica for each study subject was evaluated quantitatively by cumulative exposure measures based on historical industrial hygiene records. Measurements on confounders such as inorganic arsenic, polycyclic aromatic hydrocarbons (PAHs), and radon were also collected from the worksites. Information on cigarette smoking was obtained by interviews of the subjects or their next of kin. A significant trend of increasing risk of lung cancer with exposure to silica was found for tin miners, but not for miners working in tungsten or copper-iron mines. Concomitant and highly correlated exposures to arsenic and PAHs among tin miners were also found. Risk of lung cancer among pottery workers was related to exposure to silica, although the dose-response gradient was not significant. Risks of lung cancer were significantly increased among silicotic subjects in iron-copper and tin mines, but not in pottery factories or tungsten mines. The results of this study provide only limited support for an aetiological association between silica and lung cancer.     

An updated mortality study of workers in three major United States refineries and chemical plants.

A historical cohort study of refinery and chemical plant workers, originally observed from 1970 to 1977, was updated to the end of 1982. This cohort included 25,321 active, retired, and terminated workers at the Exxon refineries and chemical plants in Baton Rouge, Louisiana; Baytown, Texas; and Bayway/Bayonne, New Jersey. An emphasis was placed on the cancers previously reported to be increased in at least one petrochemical worker population. The population included a high proportion of retirees, providing adequate work experience and latency to evaluate risks associated with employment. Vital status was determined for 98.3% of the population and death certificates were obtained for 99.9% of the decedents. Mortality for "all causes of death" (standardised mortality ratio (SMR) = 89, 95% confidence interval (95% CI) 87-91) and for "all cancers" (SMR = 94, 95% CI 89-100) were lower than expected based on state rates. History of cigarette smoking collected from individual medical records and summarised work histories were used for subgroup analyses. There was no indication that cancers of primary interest were increased; however, blue collar workers at one plant had raised rates of kidney cancer (SMR = 246, 95% CI 146-390), which may require further evaluation.     

A nested case-control study of lung cancer among silica exposed workers in China.

In an attempt to assess whether silica induces lung cancer, a nested case-control study of 316 male lung cancer cases and 1352 controls was carried out among pottery workers and tungsten, copper-iron, and tin miners from five provinces in south central China. Exposure to dust and silica for each study subject was evaluated quantitatively by cumulative exposure measures based on historical industrial hygiene records. Measurements on confounders such as inorganic arsenic, polycyclic aromatic hydrocarbons (PAHs), and radon were also collected from the worksites. Information on cigarette smoking was obtained by interviews of the subjects or their next of kin. A significant trend of increasing risk of lung cancer with exposure to silica was found for tin miners, but not for miners working in tungsten or copper-iron mines. Concomitant and highly correlated exposures to arsenic and PAHs among tin miners were also found. Risk of lung cancer among pottery workers was related to exposure to silica, although the dose-response gradient was not significant. Risks of lung cancer were significantly increased among silicotic subjects in iron-copper and tin mines, but not in pottery factories or tungsten mines. The results of this study provide only limited support for an aetiological association between silica and lung cancer.     

A nested case-control study of stomach cancer mortality among automobile machinists exposed to metalworking fluid

PURPOSE: In a nested case-control study of 140 stomach cancer deaths (1941-1984) among 46,384 automobile workers, we examined risk in relation to lifetime exposure to metalworking fluid (MWF) in machining and grinding operations.METHODS: Exposure was defined during varying windows of biologic time (<10 years before death, 10-20 years before death, and > 20 years before death) and evaluated using a nonparametric smoothing technique and conditional logistic regression. Exposure was measured by duration, intensity (mg/m(3)), and cumulative exposure (mg/m(3)-years) to each MWF type (straight, soluble, or synthetic), as well as by duration of exposure to selected metals, additives, and components of the fluids.RESULTS: When data from three plants were combined, grinding with water-based synthetic or soluble MWF increased the risk of stomach cancer mortality. Those grinding with synthetic MWF with more than 1.3 mg/m(3)-years exposure during the 10 years just prior to death experienced a 4.4-fold risk of stomach cancer (95% CI 1.5-13.1). Increased risk was also observed among those in the highest category of soluble grinding grading exposure (OR 1.9; 85% CI 1.0-3.6). In plant-specific analysis, there was evidence of increased risk of stomach cancer associated with exposure to straight MWF and iron, as well as the water-based fluids.CONCLUSIONS: Study findings suggest that stomach cancer mortality was associated with exposure to each MWF type. Results suggesting that synthetic MWF may act as a stomach cancer promoter are of particular concern because this MWF is widely used in today's high speed grinding operations.     

Retrospective cohort mortality study of workers with potential exposure to epichlorohydrin and allyl chloride

Previous epidemiologic research has associated potential epichlorohydrin exposure with lung cancer and, in conjunction with allyl chloride exposure, to heart disease mortality. The study was designed to test both hypotheses by examining the mortality experience of 1,064 male employees (12,574 person-years) who had a minimum of 1 month work experience between 1957–1986 in the production or use of epichlorohydrin and allyl chloride and 1 year total employment duration at Dow Chemical's Texas Operations. Vital status follow-up occurred through 1989 of which there were 66 total deaths (standardized mortality ratio [SMR] = 80, 95% confidence interval [CI] 62–101). There were no significantly elevated SMRs for all malignant neoplasms, lung cancer, circulatory system disease, or arteriosclerotic heart disease when compared to external (U.S.) or internal (Texas Operations) populations. There were no apparent mortality trends with cumulative exposure analyses of potential epichlorohydrin exposure with and without accompanying allyl chloride exposure. A high prevalence of circulatory system death certificates were certified by nonphysicians in the local county and more than one third were described in nonspecific terms. The study results are not consistent with the prior hypothesized associations. However, the study results are limited by the cohort's size, duration of follow-up, relatively few number of observed and expected deaths, and the level of potential epichlorohydrin exposure experience. © 1994 Wiley-Liss, Inc.     

Retrospective cohort mortality study of workers engaged in motion picture film processing

OBJECTIVE: To assess potential health risks associated with work in a large motion picture film-processing facility. METHODS: A retrospective cohort mortality study was conducted during 1960-2000 among 2646 film workers. Job family categories, created from detailed employee work history information, were used to evaluate chemical exposure patterns. RESULTS: Overall mortality was as expected (standardized mortality ratio [SMR] = 1.1; 95% confidence interval [CI] = 1.0-1.2). Statistically significant associations were found for suicides (SMR = 2.0; 95% CI = 1.2-3.0) among the hourly workers and AIDS (SMR = 5.3; 95% CI = 1.7-12.3) among the administrative workers. Film developers had increases of respiratory cancer (SMR = 1.9; 95% CI = 1.1-3.0) and suicides (SMR = 2.4; 95% CI = 1.0-4.7), whereas film assemblers had an increase in suicides (SMR = 2.4; 95% CI = 1.2-4.4) only. CONCLUSIONS: Excess deaths resulting from suicides and AIDS among the workforce suggest that nonoccupational influences may be involved in the mortality of this cohort and warrant further investigations.     

A cohort mortality study of forestry workers exposed to phenoxy acid herbicides.

A cohort mortality study was undertaken of forestry workers at a public electrical utility who had worked for six months or more during 1950-82 and who were routinely exposed to herbicides including phenoxy acids. A total of 1222 men with 25 274 years at risk experienced 80 deaths. Ascertainment of vital state at the end of follow up was 95.5%. The male population of the province (Ontario) was used as the reference group. Overall, no excess mortality was found in this cohort relative to the reference population. A statistically significant increase in deaths occurred, however, due to suicide (SMR = 210, 95% confidence interval, 95% CI 105-376) for the cohort as a whole. No deaths were seen due to cancers such as soft tissue sarcoma and non-Hodgkin's lymphoma that have been cited by other authors as being associated with exposure to phenoxy acid herbicides. Although the cohort is not large, the absence of deaths due to these cancers is consistent with findings from other studies with sufficient numbers to allow examination of specific risks. The cohort is still young, however, and at the end of follow up most had not reached an age when increased incidence of cancer would normally be expected.