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.     

Cancer mortality in German carbon black workers 1976-98

Background

Few studies have investigated cancer risks in carbon black workers and the findings were inconclusive.

Methods

The current study explores the mortality of a cohort of 1535 male German blue‐collar workers employed at a carbon black manufacturing plant for at least one year between 1960 and 1998. Vital status and causes of death were assessed for the period 1976–98. Occupational histories and information on smoking were abstracted from company records. Standardised mortality ratios (SMR) and Poisson regression models were calculated.

Results

The SMRs for all cause mortality (observed deaths (obs) 332, SMR 120, 95% CI 108 to 134), and mortality from lung cancer (obs 50, SMR 218, 95% CI 161 to 287) were increased using national rates as reference. Comparisons to regional rates from the federal state gave SMRs of 120 (95% CI 107 to 133) and 183 (95% CI 136 to 241), respectively. However, there was no apparent dose response relationship between lung cancer mortality and several indicators of occupational exposure, including years of employment and carbon black exposure.

Conclusions

The mortality from lung cancer among German carbon black workers was increased. The high lung cancer SMR can not fully be explained by selection, smoking, or other occupational risk factors, but the results also provide little evidence for an effect of carbon black exposure.     

A cohort mortality study of U.K. carbon black workers, 1951-1996

BACKGROUND: Carbon black, a powdered form of elemental carbon is used in the manufacture of rubber products, paints, plastics, and inks. In 1974, the Health and Safety Executive initiated a cohort mortality study on possible carcinogenic effects on carbon black workers. METHODS: The mortality of a cohort of 1,147 male manual workers from five U.K. factories manufacturing carbon black was investigated for the period 1951-1996. All subjects were employed in the carbon black industry for 12 months or more, and all were first employed before 1975. Limited work histories were used to calculate estimates of individual cumulative exposure to carbon black, using a job-exposure matrix derived by the study team. RESULTS: Based on serial rates for the general population of England and Wales, significantly elevated mortality was observed in the main study cohort for all causes (Obs 372, Exp 328.7, SMR 113, P < 0.05) and for lung cancer (Obs 61, Exp 35.3, SMR 173, P < 0.001). There were highly elevated lung cancer SMRs at two of the factories, and unexceptional SMRs at the remaining three factories. There was no indication of lung cancer SMRs increasing with period from first employment. Poisson regression analyses failed to find significant trends of lung cancer risks increasing either with cumulative exposure to carbon black (4 levels) or with duration of employment at the participating factories (4 levels). CONCLUSIONS: Confident interpretation of the elevated SMRs found for lung cancer in two of the factory subcohorts is not possible but the study has been unable to link cumulative exposure to carbon black with elevated risks of lung cancer.     

Lung cancer mortality and carbon black exposure: Cox regression analysis of a cohort from a German carbon black production plant

OBJECTIVE: We undertook a lung cancer mortality analysis of 1528 German carbon black workers, followed between the years of 1976-1998, who produced furnace black, lamp black, and gas black. METHODS: We used Cox modeling across age with time-dependent covariates, ie, cumulative and mean carbon black exposure, duration of work in departments, adjusting for calendar time, a smoking indicator, and age at hire. Exposures were lagged up to 20 years. Analyses were performed with the full cohort and after restriction to an inception cohort. RESULTS: A total of 50 lung cancer deaths occurred. No positive association was found with carbon black exposure indices. Some models indicated an increasing risk across duration of work in the lamp black producing department. CONCLUSIONS: Our results do not suggest that carbon black exposure is a human lung carcinogen. The lamp black results, if no artifact, may point at historical exposures to gaseous polycyclic aromatic hydrocarbons.     

Epidemiologic study of cancer mortality among Israeli asphalt workers

BACKGROUND: We describe the results of a cancer mortality study among asphalt workers in Israel. METHODS: Personal identifiers and employment histories of 2,176 workers were extracted from company records. RESULTS: Mortality from all malignant neoplasms was significantly reduced in the whole cohort (SMR 0.68, 95% confidence interval (CI) 0.56-0.83). SMR for lung cancer was elevated in workers exposed to bitumen (SMR 1.05, 95% CI 0.62-1.66). No significant elevation or reduction in mortality was observed in relation to a specific site. SMRs for lung cancer was higher among ever exposed to bitumen than among unexposed. There was no association between lung cancer risk and estimated exposure to bitumen fume, and no dose-response was apparent. CONCLUSIONS: While the results of this cohort study indicate a slightly increased SMR for lung cancer, it did not produce evidence of a causal link between lung cancer and exposure to bitumen fume.     

Mortality and cancer incidence in Ontario glass fiber workers

BACKGROUND: In a previous cohort study of glass fiber manufacturing, we found a significant increase in lung cancer. This study extends the follow-up period. METHODS: We conducted a historical prospective study of 2557 men employed in producing glass wool. We obtained work histories, causes and dates of death, and date and site of cancer diagnoses. We computed standardized mortality and incidence ratios (SMR, SIR). RESULTS: The overall SMR for lung cancer was 163 (95% CI = 118-221). The SMR did not vary consistently by duration of employment and time since first employment. However, plant workers with >20 years' employment and >40 years since first exposure had an SMR for lung cancer of 282 (95% CI = 113-582). The SMR dropped with later date of first exposure, but the trend was non-significant. There was an unexpected overall increase in kidney cancer incidence. DISCUSSION: The increase in lung cancer is greater than in other cohorts of glass fiber workers. Since exposure data are lacking from the early years of the plant, we cannot state if the excess was due to glass fibers, other work exposures or other reasons.     

Mortality patterns among men in the motor vehicle manufacturing industry

This retrospective follow-up study evaluates the mortality experience of 123,232 male hourly workers employed at a motor vehicle manufacturing company in 1973. Company computerized personnel records were used to identify subjects and to obtain their employment history. Follow-up through December 31, 1985 was conducted using company, state, and national data sources. The mortality rates of the cohort were compared with the rates of the United States (U.S.) general population of white or black men, adjusting for age and calendar time, and using the standardized mortality ratio (SMR) as the measure of association. The overall mortality rate of cohort members is lower than the U.S. rate by 11% among whites (11,060 observed/12,427 expected deaths; SMR = 89) and by 24% among blacks (3,744/4,926 deaths; SMR = 76). These low mortality rates reflect deficits of diseases other than cancer. Cancer SMRs are 99 for whites and 90 for blacks. There are slight excesses of stomach cancer (SMR = 113) and of lung cancer (SMR = 108) among whites and of cancer of the large intestine and rectum (SMR = 114) and of the lymphopoietic tissue (SMR = 111) among blacks. Both whites and blacks have a large deficit of buccal cancer and pharynx cancer, and blacks also have a deficit of esophagus cancer. The cohort's overall deficit of deaths is due largely to the favorable mortality experience of active workers. In contrast, white subjects who have left active employment have an 11% mortality excess, and inactive black subjects have a mortality rate that is similar to the general population rate. The increased mortality among inactive whites is not limited to any one particular disease category. This pattern may reflect illness-related employment termination and generalized confounding by socioeconomic status, although the study does not rule out a relationship between workplace exposures and specific diseases. © 1993 Wiley-Liss, Inc.     

Lung cancer mortality and carbon black exposure: a nested case-control study at a German carbon black production plant

OBJECTIVE: The objective of this study was to conduct a case-control study of lung cancer nested within a cohort of 1528 German carbon black workers, 1976-1998. METHODS: The authors conducted risk-set sampling of two controls matched on year of birth and conditional logistic regression modeling of cumulative carbon black exposure, duration of work in different departments, feedstock contact, asbestos exposure, smoking, age at hire, exposures before the carbon black job, and serving as a soldier in World War II or being a prisoner of war. Analyses were performed with both the full cohort and members of an inception cohort subset. Exposures were lagged by 10 years. RESULTS: Analysis of 50 lung cancer deaths showed no association to carbon black exposure. CONCLUSIONS: Carbon black exposure was not linked to lung cancer risk. Suggestions of positive associations with asbestos exposure, feedstock contact, and work in specific departments are inconclusive due to small numbers.     

Cancer mortality in a cohort of male German iron foundry workers

BACKGROUND: Observations of an increased incidence of cancers of the upper aero-digestive tract (pharynx, esophagus, larynx, lung) among workers of local German foundries gave rise to concern about a potentially elevated occupational risk of those cancer sites. The purpose of the study was to examine whether occupational exposure in iron foundries increases the risk of cancer. METHODS: A historical cohort study of 17,708 male German production workers in 37 iron foundries who were first employed in 1950-1985 with a minimum employment period of 1 year was initiated. Employment and occupational histories were collected. Mortality was compared with that of the German general population during 1950-1993 using a new method for computing the SMR when not all causes of death are available (called SMR*). RESULTS: Mortality from all causes was elevated to SMR = 115.4 (95% confidence interval (CI) = 111.9-119.1), as was for total cancer (SMR* = 123.8, CI = 102.1-152.6), especially cancers of the lung (SMR* = 163.9, CI = 123.9-223.0) and liver (SMR* = 322.5, CI = 149.5-844.8), and diseases of the respiratory system (SMR* = 147.6, CI = 100.4-221.5). Non-significant elevations of mortality were also found for cancers of the mouth and pharynx (SMR* = 153.5, CI = 82.3-359.8) and larynx (SMR* = 173.1, CI = 85.5-550.5). Mortality from various causes of death was higher among workers with shorter exposure periods than among long-term employees. The elevated mortality persisted for years and decades after termination of employment. CONCLUSIONS: The results provide further evidence for an increased risk of lung cancer and possibly other cancers of the upper aero-digestive tract among foundry workers. Special attention should be paid to the strongly increased mortality from liver cancer and the mortality pattern among employees having terminated work.     

An updated mortality study of workers at a petroleum refinery in Beaumont,Texas

The mortality experience of 7,119 workers who were employed at a Beaumont, Texas, refinery for at least 1 year between 1945 and 1987 was investigated. Mortality analyses based on standardized mortality ratios (SMRs) and 95% confidence intervals (95%CI) showed overall mortality was significantly lower than expected compared with the U.S. general population (SMR <=;=> 82, 95%CI = 79–86). Total cancer mortality was also lower than expected (SMR = 92, 95% CI = 84–100). Significant mortality deficits from several malignant and nonmalignant diseases were reported. A significant mortality increase in the broad category of lymphatic and hematopoietic cancers was found (SMR = 133, 95%CI = 103–170). This increase was attributed to a nonsignificant elevation in leukemia of all cell types combined (SMR = 139, 95%CI = 92–201) and a borderline significant increase in other lymphatic tissue cancer (SMR = 158, 95%CI = 101–235). The elevation in leukemia was confined to workers hired before 1950. Furthermore, the leukemia excess was shown to have peaked during the 1960s, with mortality no longer elevated post-1980. Analyses of cell type-specific leukemias showed a similar temporal pattern for acute myeloid leukemia (AML) which was not significantly elevated (SMR = 136, 95%CI = 59–268). Mortality from other leukemia cell types was similar to or lower than expected. Mortality from non-Hodgkin's lymphoma (NHL) (SMR = 140, 95%CI = 88–211) and multiple myeloma (MM) (SMR = 121, 95%CI = 55–230) were increased, but neither was statistically significant nor likely to be related to refinery employment. No death from asbestosis was reported, and mortality from mesothelioma and pulmonary fibrosis was lower than expected. Lung cancer mortality for the overall cohort was similar to expected. For the overall cohort, analyses by duration of employment and time since first employment showed no evidence of any trends for increasing cause-specific mortality. Separate analyses of male workers employed in operator jobs showed mortality patterns that were more favorable than those of the total cohort. Maintenance craftworkers showed statistically significant elevations in mortality for prostate cancer (SMR = 145, 95%CI = 107–194), leukemia (SMR = 179, 95%CI = 111–273), and other lymphatic tissue cancer (SMR = 233, 95%CI = 138–368). Detailed analyses indicated that, among maintenance craftworkers, mortality was elevated for AML, NHL, and MM, but none was significant. Furthermore, no upward trend by duration of maintenance jobs was observed. A small increase of lung cancer was observed among maintenance craftworkers (SMR = 120, 95%CI = 99–145), which was borderline significant. No relationship between lung cancer and duration of maintenance employment was found. In contrast, a deficit of pulmonary fibrosis was reported among maintenance craftworkers (SMR = 62, 95%CI = 17–159). These findings are discussed in conjunction with results from other refinery studies, and the limitations of the study are discussed. Am. J. Ind. Med. 33:61–81, 1998. © 1998 Wiley-Liss, Inc.     

Lung cancer mortality and carbon black exposure: uncertainties of SMR analyses in a cohort study at a German carbon black production plant

OBJECTIVE: We undertook a sensitivity analysis of the lung cancer standardized mortality ratios (SMRs) in a study of 1522 German carbon black workers from 1976 to 1998. METHODS: We applied results from a case-control study to adjust the SMR for smoking habits and exposures experienced before the carbon black job. In addition, sensitivity to reference rates was explored. RESULTS: On the basis of 47 lung cancer deaths, the SMRs were 1.62, 1.72, and 2.08 (local, state, and national rates, respectively). Adjustment for previous exposures and smoking yielded additional correction factors of 0.64 or 0.74, varying with the chosen reference. CONCLUSIONS: Lung cancer SMRs (95% confidence intervals) for the full cohort ranged from 1.20 (0.88-1.59) to 2.08 (1.53-2.77) in this sensitivity analysis. Thus, overall SMRs are only weak measures of causal associations and should be complemented by internal modeling of exposure effects whenever possible.     

Lung cancer mortality in a french cohort of hard-metal workers

A cohort mortality study was carried out among workers of a plant producing hard metals using cobalt as a binder. This study was aimed at assessing possible lung cancer risks in relation with cobalt exposure. Seven hundred nine male workers with at least 1 year of employment were included in the cohort and followed for mortality from 1956 to 1989. Job histories were provided by the administration of the plant, whereas smoking habits were collected from medical records and by interview. The causes of deaths were ascertained from hospital and general practitioner records. The observed numbers of deaths (obs) were compared with the expected based on national rates with adjustment for age, sex, and calendar time (standardized mortality ratio; SMR). The overall mortality did not differ from that expected (obs = 75, SMR = 1.05), whereas mortality due to lung cancer was in significant excess (obs = 10, SMR = 2.13). This excess was higher among workers employed in the areas with the highest exposure (obs = 6, SMR = 5.03). No trend was observed, however, with duration of employment or time since first employment. Smoking data were available for 81% of the workers and 69% of the deceased and showed that smoking alone does not account for these lung cancer excesses, yet, because of the small numbers involved, no firm conclusion should be drawn from this study.     

Occupational risk factors for mortality from stomach and lung cancer among rubber workers: an analysis using internal controls and refined exposure assessment

OBJECTIVES: To determine occupational risk factors for stomach and lung cancer among workers in the German rubber industry. METHODS: A cohort of all male German rubber workers (n = 11,633) who had been employed for at least one year in one of five study plants and who were alive and actively employed or retired on 1 January 1981 was followed for mortality from 1 January 1981 through December 1991. A subcohort of n = 8,933 workers who were hired after 1 January 1950 was defined to focus on working conditions in the more recent rubber industry. Work histories were reconstructed using routinely documented 'cost centre codes' and classified into six work areas as well as subgroups of some work areas. The work areas are: 1. preparation of materials, 2. production of technical rubber goods, 3. production of tyres, 4. storage and dispatch, 5. maintenance, 6. others. Standardized mortality ratios (SMR) and Cox proportional hazards models were calculated for each of the work areas (>1 year of employment in the respective work area). Hazard rate ratios were adjusted for age (time marker) and stratified for year of hire (1950-1959, > or =1960) and years of employment in the respective work area (1-9 years, > or =10 years); years of employment were lagged 10 years to account for latency. RESULTS: Compared to the national reference population mortality from cancer of stomach (observed 44, SMR = 117; 95% CI: 85-157) and lung (observed 154, SMR = 123; 95% CI: 104-144) was slightly increased. Using internal controls we observed excess deaths from stomach cancer in work area 1 (relative risk [RR] = 2.3; 95% CI: 1.2-4.2) and from lung cancer in work areas 1 (RR = 1.7; 95% CI: 1.2-2.3), 2 (RR = 1.5; 95% CI: 1.1-2.1), and 3 (RR = 1.3; 95% CI: 0.9-1.8). On the basis of cumulative years of employment an exposure response relationship was observed for mortality from both cancer sites among a subcategory of work area 1: weighing and mixing. Increased risks were also seen for lung cancer among workers employed in production of technical rubber goods. CONCLUSION: Our results support an association between an excess mortality from stomach and lung cancer and employment in early production stages of rubber manufacturing, especially weighing and mixing. This may point to an aetiologic role of asbestos or carbon black. For stomach cancer additional risk factors, e.g. exposure to dust and talc, deserve further investigation. The results of the present study do not support a causal role of nitrosamines for stomach or lung cancer.     

Cancer mortality among magazine printing workers.

OBJECTIVE: After an inquiry from the employees of an offset printing plant, a historical cohort study was conducted to investigate cancer mortality among these workers. METHODS: The cohort comprised 262 men, who contributed 2771 person-years of observation. 16 deaths were identified during the follow up period (1980-91). Expected numbers of deaths were derived from age specific regional rates. Standardised mortality ratios (SMR) and 95% confidence intervals (95% CIs) were calculated. RESULTS: An increased cancer mortality was found after 10 years of employment (SMR 213, 95% CI 98 to 405, based on nine deaths), mainly due to a high mortality from lung cancer (SMR 381, 95% CI 104 to 975, four deaths), and from oesophageal cancer (SMR 1049, 95% CI 216 to 3065, three deaths). For workers with at least 20 years since the start of employment, the SMR was 262 (95% CI 105 to 540) for all cancer sites, 447 (95% CI 92 to 1306) for lung cancer, and 1094 (95% CI 132 to 3952) for oesophageal cancer. The increased cancer mortality was concentrated among pressmen. CONCLUSION: Although based on small numbers, the findings suggest an increased risk of cancer among these workers, which should be further investigated.     

Cause of death among workers of a refinery in Rome]

We evaluated mortality among subjects employed in an oil refinery plant in Rome, Italy. We studied two subgroups of refinery employees: blue collar and white collar workers. A total of 682 men (505 blue collars, 148 white collars, 29 unknown) employed between 1965 and 1992, were followed up for mortality since employment in the plant to July 1999. Standardized Mortality Ratios (SMR), and their 90% Confidence Intervals (90% CI), comparing mortality rates of the cohort members with those of the general population of the Lazio region. For blue collar workers, we performed analyses by latency since first employment and by duration of employment for selected cancer sites. We observed 94 total deaths (100.8 expected) (SMR = 0.93; 90% CI = 0.78-1.11) among blue collar workers and 16 total deaths (31.7 expected) (SMR = 0.50; 90% CI = 0.32-0.77) among white collar workers, and a large deficit of deaths from non-neoplastic cardiovascular diseases (respectively SMR = 0.60; 90% CI = 0.41-0.86 and SMR = 0.18; 90% CI = 0.03-0.56). All cancer mortality was slightly increased only in blue collars (SMR = 1.27 CI = 0.97-1.65). There was an excess risk from cancer of the lung (20 obs SMR = 1.80, 90% CI = 1.19-2.62), bladder (5 obs SMR = 3.19, 90% CI = 1.26-6.72), and benign/unspecified cancer of the brain (4 obs SMR = 4.11, 90% CI = 1.12-10.6). The lower mortality from cardiovascular disease indicates the presence of a strong healthy worker effect. The findings of elevated mortality from cancer of the lung and bladder in blue collar workers are in agreement with those of other studies. Confounding factors from cigarette smoking might have played only a marginal role in influencing the results. Exposure to polynuclear aromatic hydrocarbons (PAHs) is a plausible explanation for the excesses found.     

A cohort mortality study of employees in the U.S. carbon black industry

OBJECTIVES: The objectives of this study are to evaluate historical mortality patterns, especially due to cancers, among employees of the U.S. carbon black industry and to address the methodological shortcomings of previous U.S. mortality studies. METHODS: We followed mortality of 5011 workers employed 1 year or more since the 1930s at 18 carbon black facilities through December 31, 2003. Age-, race-, sex-, and calendar year-adjusted standardized mortality ratios (SMRs) were calculated using state-specific mortality rates. RESULTS: Follow up was 96% complete. All-cause (SMR = 0.74, 95% confidence interval [CI] = 0.70-0.78) and all-cancer mortality (SMR = 0.83, 95% CI = 0.74-0.92) showed significant deficits. No excess was observed from lung (SMR = 0.97, 95% CI = 0.82-1.15) or bladder (SMR = 0.93, 95% CI = 0.47-1.87) cancers or from nonmalignant respiratory diseases (SMR = 0.99, 95% CI = 0.83-1.18). No trends were seen with duration of employment or time since hire for any cause of death. CONCLUSION: Employment in carbon black production in the United States seems not to be associated with increased mortality overall, cancer overall and, in particular, lung cancer. Further research, however, incorporating a detailed exposure assessment is needed to determine whether exposure to carbon black at high levels may be associated with an increased risk of cancer.     

Follow-up study of chrysotile asbestos textile workers: Cohort mortality and case-control analyses

Previous studies of mortality among white males employed in a Charleston, South Carolina asbestos textile plant using chrysotile demonstrated significant excess mortality due to asbestos-related disease and a steep exposure-response relationship for lung cancer. This cohort was further studied by adding 15 years of follow-up and including mortality among white female and black male workers. Nested case-control analyses were undertaken to further explore possible differences in lung cancer risk by textile operation as well as possible confounding by mineral oil exposures. Preliminary data for white males have been previously published. White males experienced statistically significant excess mortality due to lung cancer (standardized mortality ratio [SMR] = 2.30; confidence interval [CI] = 1.88–2.79), all causes (SMR = 1.48; CI = 1.38–1.58), all cancers (SMR = 1.50; CI = 1.29–1.72), diabetes mellitus (SMR = 2.05; CI = 1.18–3.33), heart disease (SMR = 1.41; CI = 1.26–1.58), cerebrovascular disease (SMR = 1.50; CI = 1.08–2.02), pneumoconiosis and other respiratory diseases (SMR = 4.10; CI = 3.10–5.31), and accidents (SMR = 1.49; CI = 1.15–1.91). Among white females, statistically significant excesses occurred for lung cancer (SMR = 2.75; CI = 2.06–3.61), all causes (SMR = 1.21; CI = 1.11–1.32), pneumoconiosis and other respiratory diseases (SMR = 2.40; CI = 1.53–3.60), and other respiratory cancers (SMR = 14.98; CI = 4.08–38.7). Among the total cohort of black males, the only statistically significant excess observed was for pneumoconiosis (SMR = 2.19; CI = 1.23–3.62). Based on historical exposure measurements at the plant, there was a positive exposure-response relationship for both lung cancer and pneumoconiosis. Data for the entire cohort demonstrate an increase in the lung cancer relative risk of 2–3% for each fiber/cc-year of cumulative chrysotile exposure. This relationship was more consistent for the white male workers. The excess risk for lung cancer among white males and females appeared to occur at cumulative exposures lower than those for black males. Possible reasons for the lesser lung cancer risk among black males include less smoking and differences in airborne fiber characteristics experienced by black males as a result of plant job placement patterns. The case-control analysis found employment in preparation and carding operations (where most of the black males worked) to be associated with a slightly reduced lung cancer risk, although not statistically significant, whereas spinning and twisting employment was associated with a statistically significant increased lung cancer risk compared to other plant operations. Airborne fiber size data, determined by transmission electron microscopy, demonstrated slightly longer fibers in spinning and twisting compared to other textile operations. Case-control analyses demonstrated little effect of mineral oil exposures on the lung cancer exposure-response estimates. Two deaths due to mesothelioma were observed among this cohort.     

Mortality of workers exposed to methylene chloride employed at a plant producing cellulose triacetate film base.

OBJECTIVE: To study mortality among 1785 employees of a factory that produced cellulose triacetate film base at Brantham in the United Kingdom. Also, to investigate patterns of mortality after exposure to methylene chloride; in particular, mortality from liver and biliary tract cancer, lung cancer, pancreatic cancer, and cardiovascular disease. SUBJECTS AND METHODS: All male employees with a record of employment at the film factory in 1946-88. A total of 1473 subjects worked in jobs that entailed exposure to methylene chloride. The mean duration of exposure was nine years at 19 ppm (eight hour time weighted average). RESULTS: In the cohort, 334 deaths were identified up to 31 December 1994. Mortalities for the cohort were compared with national and local rates and expressed as standardised mortality ratios (SMR). In the subcohort of workers exposed to methylene chloride, substantially reduced mortalities compared with national and local rates were found for all causes, all cancers, and the principal cancer sites of interest. The significantly reduced lung cancer mortalities in exposed workers (SMR 48) seemed to reflect the restrictions on smoking at the workplace. In contrast, mortality from ischaemic heart disease in exposed workers, although lower than national rates (SMR 92), was slightly increased compared with local rates. However, mortality from ischaemic heart disease was lower in active employees (SMR 83) where a direct effect of exposure to methylene chloride should be concentrated. No in service mortality due to ischaemic heart disease was found in workers with the highest cumulative exposure (> or = 800 ppm-years). CONCLUSIONS: The study provided no indication that employment at the plant, or exposure to methylene chloride, had adversely affected the mortalities of workers.     

Bayesian bias adjustments of the lung cancer SMR in a cohort of German carbon black production workers

Background  

A German cohort study on 1,528 carbon black production workers estimated an elevated lung cancer SMR ranging from 1.8-2.2 depending on the reference population. No positive trends with carbon black exposures were noted in the analyses. A nested case control study, however, identified smoking and previous exposures to known carcinogens, such as crystalline silica, received prior to work in the carbon black industry as important risk factors.     

Lung cancer risk among refractory brick workers exposed to crystalline silica: a retrospective cohort study.

We conducted a retrospective cohort study among 1,022 refractory brick workers exposed to crystalline silica. Mortality from lung cancer (SMR = 1.77) and respiratory diseases (SMR = 3.15) was elevated in workers first employed less than or equal to 1957 who are likely to have shared the highest exposure to crystalline silica. Workers with at least 19 years of cumulative employment in the plant experienced particularly increased risks for lung cancer (SMR = 2.01) and respiratory diseases (SMR = 3.89). Relative mortality from these specific causes increased with years since first employment (that is, first exposure) and decreased with age at first employment. Indirect adjustment for smoking habits and the lack of excess mortality from cardiovascular diseases and emphysema indicated little effect of smoking on the increased risks for lung cancer and respiratory diseases.