Mortality among employees engaged in chemical manufacturing and related activities

Brain Cancer in Workers Employed at a Laboratory Research Facility

BACKGROUND

An earlier study of research facility workers found more brain cancer deaths than expected, but no workplace exposures were implicated.

METHODS

Adding four additional years of vital-status follow-up, we reassessed the risk of death from brain cancer in the same workforce, including 5,284 workers employed between 1963, when the facility opened, and 2007. We compared the work histories of the brain cancer decedents in relationship to when they died and their ages at death.

RESULTS

As in most other studies of laboratory and research workers, we found low rates of total mortality, total cancers, accidents, suicides, and chronic conditions such as heart disease and diabetes. We found no new brain cancer deaths in the four years of additional follow-up. Our best estimate of the brain cancer standardized mortality ratio (SMR) was 1.32 (95% confidence interval [95% CI] 0.66-2.37), but the SMR might have been as high as 1.69. Deaths from benign brain tumors and other non-malignant diseases of the nervous system were at or below expected levels.

CONCLUSION

With the addition of four more years of follow-up and in the absence of any new brain cancers, the updated estimate of the risk of brain cancer death is smaller than in the original study. There was no consistent pattern among the work histories of decedents that indicated a common causative exposure.

Inhalation carcinogenicity and chronic toxicity of carbon tetrachloride in rats and mice

Carcinogenicity and chronic toxicity of carbon tetrachloride were examined by inhalation exposure of 50 F344 rats and 50 BDF1 mice of both sexes to carbon tetrachloride at 0 (clean air), 5, 25, or 125 ppm (v/v) for 6 h/day, 5 days/wk, for 104 wk. Incidences of hepatocellular adenomas and carcinomas in rats and mice of both sexes and of adrenal pheochromocytomas in mice of both sexes were significantly increased dose-dependently. Hepatocellular carcinomas and cirrhosis significantly occurred in the 125-ppm-exposed rats of both sexes, and 3 cases of hepatocellular carcinomas and increased incidences of hepatic altered cell foci were noted in the 25-ppm-exposed female rats. Hepatocellular carcinomas were induced in mice of both sexes at 25 and 125 ppm, and hepatocellular adenomas occurred in females at 5 ppm without any degenerative or necrotic change in hepatocytes. Hepatocellular carcinomas metastasized to the lung. The chronic hepatotoxicity was characterized by cirrhosis, fibrosis, and fatty change in rats, and ceroid deposition, bile-duct proliferation, and hydropic change in mice. Survival rates were decreased in the 125-ppm-exposed rats and mice of both sexes and in the 25-ppm-exposed female mice, in association with decreased body weights. The decreased survival rates were considered to be causally related to both various tumors including hepatocellular carcinomas and severe chronic progressive nephropathy in rats and to hepatocellular carcinomas in mice. This study provided clear evidence of carcinogenicity for carbon tetrachloride in rats and mice. A cytotoxic-proliferative and genotoxic mode of action for carbon tetrachloride-induced hepatocarcinogenesis was suggested.

Occupation, hobbies, and acute leukemia in adults

Occupational and industrial exposures have been implicated in the etiology of leukemia, yet uncertainty remains regarding potential high risk occupations. We examined the associations between self-reported occupations and hobbies and acute leukemia risk using data from 811 cases and 637 controls participating in a case-control study in the U.S. and Canada. We found that several occupations may increase the risk of acute leukemia, particularly occupations related to petroleum products, rubber, nuclear energy, munitions, plastics, and electronics manufacturing. Differences were noted according to histological type. Other occupations and hobbies were not clearly associated with risk.

Health findings from a mortality and morbidity surveillance of refinery employees

PURPOSE

To present results from a prospective mortality (1973-1998) and morbidity (1990-1998) surveillance of a refinery population in California.

METHODS

Mortality and illness-absence data were extracted from the Shell Oil Company's Health Surveillance System (HSS). Mortality data were compared to the United States, the state of California, and Contra Costa County, where the refinery is located. Morbidity data were compared to other company manufacturing employees. The standardized mortality/morbidity ratio (SMR/SMbR) was used as a measure of risk. Morbidity frequency and duration of absence were calculated by age, sex, and four health risk factors (smoking, high blood pressure, hypercholesterolemia, and obesity).

RESULTS

With the United States as a comparison, the all causes combined SMR was 0.84 [95% confidence interval (CI) = 0.78-0.90], and the SMR for all cancer was 0.75 (95% CI = 0.64-0.88). Statistically significant deficits in mortality were found for lung cancer (SMR = 0.60) and leukemia (SMR = 0.26). Morbidity frequency and duration of absence among smokers were substantially higher than those of nonsmokers. Similar results were also noted for obese employees when compared to those of normal weight.

CONCLUSIONS

Regardless of the comparison population, significantly fewer deaths were seen for all causes combined, all cancer, lung cancer, and leukemia. The study also showed no increased mortality from cancer of the stomach, kidney, skin, prostate, and brain. The increased morbidity frequency and duration of absence were associated with the presence of known health risk factors. These study findings are useful in setting priorities for medical programs and directing efforts such as health promotion and disease prevention strategies.

Occupational risk factors for pancreatic cancer: a case-control study based on death certificates from 24 U.S. states

BACKGROUND

The relation between occupational exposure and pancreatic cancer is not well established. A population-based case-control study based on death certificates from 24 U.S. states was conducted to determine if occupations/industries or work-related exposures to solvents were associated with pancreatic cancer death.

METHODS

The cases were 63,097 persons who died from pancreatic cancer occurring in the period 1984-1993. The controls were 252,386 persons who died from causes other than cancer in the same time period.

RESULTS

Industries associated with significantly increased risk of pancreatic cancer included printing and paper manufacturing; chemical, petroleum, and related processing; transport, communication, and public service; wholesale and retail trades; and medical and other health-related services. Occupations associated with significantly increased risk included managerial, administrative, and other professional occupations; technical occupations; and sales, clerical, and other administrative support occupations. Potential exposures to formaldehyde and other solvents were assessed by using a job exposure matrix developed for this study. Occupational exposure to formaldehyde was associated with a moderately increased risk of pancreatic cancer, with ORs of 1.2, 1.2, 1.4 for subjects with low, medium, and high probabilities of exposure and 1.2, 1.2, and 1.1 for subjects with low, medium, and high intensity of exposure, respectively.

CONCLUSIONS

The findings of this study did not suggest that industrial or occupational exposure is a major contributor to the etiology of pancreatic cancer. Further study may be needed to confirm the positive association between formaldehyde exposure and pancreatic cancer. Published 1999 Wiley-Liss, Inc.

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.

Mortality among workers at a plastics manufacturing and research and development facility: 1946-1988

Mortality through 1988 was studied for 5,932 male employees who worked between January 1, 1946 and December 31, 1967 at a New Jersey plastics manufacturing and research and development facility. The cohort was followed for an average of 32 years and included 1,859 deaths. Potential exposures included asbestos, formaldehyde, and polyvinyl chloride (PVC). Mortality rates for the cohort were compared to both U.S. and state mortality rates, and analyses were also performed by lagging duration of employment. Based on U.S. rates, mortality among hourly males (n = 3,853) from all cancers was similar to expected [standardized mortality ratio (SMR), 102; 95% confidence interval (CI), 92-114]. Excess mortality among hourly workers was seen for pancreatic cancer (SMR, 146; 95% CI, 95-216) and "malignancies of other parts of the respiratory system" (SMR, 373; 95% CI, 121-870). The latter excess was due entirely to five deaths from pleural mesothelioma. There were no deaths identified due to nasal cavity or nasopharyngeal cancers, or angiosarcoma of the liver. Mortality from leukemia among research and development workers (n = 1,421) was significantly elevated (SMR, 265; 95% CI, 115-524) and related to assignment to process development. This study verifies the excess of pancreatic cancer among workers at the facility seen in earlier studies and observes excesses of mesothelioma due to asbestos exposure and leukemia in process development workers.

Pancreatic cancer among workers processing synthetic resins

A nested case-control study was conducted to investigate whether an excess of pancreatic cancer, identified in a cohort mortality study with follow-up from 1946 through 1988, was associated with potential workplace exposures at a New Jersey plastics manufacturing and research and development facility. The study population included 28 male pancreatic cancer cases and 140 randomly selected controls, matched on year of birth and at risk (alive) at the time of the case death. Using plant work history records, department assignments for the two groups were compared according to duration and time since first assignment. Workers assigned to a work area that processed vinyl resins and polyethylene (PE) were shown to be at increased risk. Men assigned more than 16 years to this department had a significantly increased risk ratio of 7.15 (95% confidence intervals [CI]: 1.28-40.1). No excess was seen with shorter duration assignments. Seven of the nine cases began working in this area in the 1940s. Average latency was 32 years, and all but three cases worked 20 years or more in this unit. Over the study period, significant exposure-related process changes occurred, in addition to the use of numerous chemical additives. Although vinyl and PE processing operations could not be analyzed separately, the pancreatic cancer excess is more likely to be related to vinyl processing. Identification of a causative agent or combination of agents would require investigations with more detailed exposure information.

Mortality due to pancreatic and lymphopoietic cancers in chlorohydrin production workers

Men assigned to the chlorohydrin unit of Union Carbide's South Charleston plant in the Kanawha Valley of West Virginia were followed up for mortality from 1940 to the end of 1988. This 10 year update was conducted to verify previous findings of excesses of cancer among the 278 men assigned to the chlorohydrin unit, which primarily produced ethylene chlorohydrin from 1925 to 1957. This process produced ethylene dichloride and bischloroethyl ether as byproducts. Mean duration of assignment was 5.9 years and mean duration of follow up was 36.5 years. Standardised mortality ratios (SMRs) were calculated based on comparisons with the United States white male population. Duration-response trends were assessed by internal comparisons with two different groups of unexposed chemical workers in the Kanawha Valley. The evidence that the earlier finding of an excess of pancreatic cancer was work related is strengthened by the occurrence of two additional cases (0.9 expected). The SMR for pancreatic cancer was 492 (95% CI 158-1140), based on eight observed v 1.6 expected deaths. There were no additional deaths due to leukaemia, but the three to four-fold excess risk for lymphopoietic cancers persisted due to new cases of non-Hodgkin's lymphoma and a death from multiple myeloma. The SMR for lymphatic and haematopoietic cancers was 294 (eight observed v 2.7 expected; 95% CI 127-580). Pronounced increases in risk were seen for total cancer, pancreatic cancer, all lymphatic and haematopoietic cancers, and leukaemia with increasing durations of assignment to the chlorohydrin unit. Most of the cases were first assigned to the unit in the 1930s when chemical manufacturing was in its infancy and exposures were less controlled. These data are insufficient to identify conclusively the causative agent or agents. The weight of evidence, however, based on probable exposure, known toxicity of the chemicals, and animal responses suggest that high exposures to ethylene dichloride, perhaps in combination with other chlorinated hydrocarbons, is the most likely explanation.

Mortality of professional chemists in England and Wales, 1965-1989

Several studies on the mortality of chemists have revealed a lower overall mortality but an excess of deaths from certain diseases, in particular, cancers. This study determined the causes of mortality of 4,012 chemists among 14,884 members of The Royal Society of Chemistry who were followed for a period of 25 years. The results demonstrated consistency with other studies. There was an overall low mortality rate, with fewer deaths than expected from cancers, but an excess mortality from lymphatic and hematopoietic cancers, in particular leukemias. There was an excess of deaths from certain gastrointestinal cancers. There was reduced mortality from respiratory diseases, including lung cancers, and from cardiovascular disease. New findings reported in this study are increased mortality from cancers of the duodenum and kidney, certain skin cancers, mental disorders, and diseases of the nervous system.

A comparative ecological study of selected cancers in Kanawha County, West Virginia

This study compares mortality rates for selected causes of death in Kanawha County, West Virginia, to rates reported in a number of geographically defined populations for 1950-1984. Specific conditions selected for study included cancers of the biliary passages and liver, the bladder and other urinary organs, and the central nervous system (CNS), as well as leukemia and aleukemia, lymphosarcoma and reticulosarcoma, Hodgkin's disease, and cancer of all other lymphopoietic tissue. The analysis made use of several techniques for the investigation of ecological data, including the modeling of rates using Poission regression. The primary findings of this study concern two subgroups of cancers of the lymphatic and hematopoietic tissue: (1) leukemia and aleukemia, and (2) lymphosarcoma and reticulosarcoma. For both subgroups of cancers, white male residents of Kanawha County show evidence of significantly elevated mortality rates over the 35-year period of this study.

General mortality and respiratory cancer among a cohort of male chemical workers in California

Cohort mortality and nested case-control studies were conducted involving 2,901 men employed 1 year or more between 1940 and 1986 at any of four California facilities of a major chemical company. Employees experienced fewer deaths from each of the major causes than were expected based on U.S., California, and local county mortality rates. Respiratory cancer was significantly elevated in one socioeconomic category comprised of operators (SMR = 157, 95% CI = 109-220). The 34 cases who died from respiratory cancer and 136 matched controls, all of whom were operators, were included in a nested case-control study. Departments in which subjects had worked were grouped into 13 work assignment or product categories by an industrial hygienist without knowledge of case-control status. Smoking habits and other occupational exposures were ascertained by telephone interview from subjects or surrogate-responders. As expected, current cigarette smoking was strongly related to respiratory cancer. After adjustment for smoking, cases were significantly more likely than controls to have ever worked in one of the 13 work areas (supervision, services, and business support). However, no dose-response relationship was evident with duration of employment in this work area and the departments involved were associated with plant security and not chemical production. Results were similar when a 15-year latency period was assumed. These findings suggest that the excess of respiratory cancer mortality among operators was most likely due to differences in cigarette smoking or other factors not ascertained, rather than to a specific occupational exposure.

Occupational exposures to styrene in Denmark 1955-88

An assessment of the occupational exposure to styrene and associated chemicals in Denmark was carried out by retrieving all measurements from the archives of the Danish National Institute of Occupational Health. A total of 2,528 air samples containing styrene had been collected from 256 workplaces during the years 1955-88 and analyzed by the chemical laboratory at the Institute. The mean for all samples was 265 mg/m3. The concentration decreased from 714 mg/m3 in the early period (1955-70) to 172 mg/m3 in the late period (1981-88). Spraying and unspecified lay-up and production of boats, carriages, and stationary containers were associated with the highest concentration. A total of 34 chemicals were measured. The most frequent co-contaminant to styrene was acetone, which was measured in 2,263 samples with a mean concentration of 131 mg/m3. Dichloromethane was measured in 208 samples with a mean concentration of 51 mg/m3, xylene in 148 samples with a mean concentration of 49 mg/m3, and toluene in 116 samples with a mean concentration of 113 mg/m3. The study was undertaken to analyze historical styrene concentrations in air to aid in the selection of industrial cohorts to be included in epidemiologic studies.

Assessment of exposure to chemicals in a complex work environment

Exposure information was evaluated for two large chemical manufacturing facilities and a research and development center in support of occupational health studies of employees assigned to these facilities. Methodology and rationale underlying the exposure categorization are provided, and descriptive exposure statistics are presented for a sample of 774 employees. Analysis of work patterns and exposure profiles revealed that 1) employee transfers among various production work areas did not follow a predictable pattern, 2) over 41% of the chemicals identified were present in multiple work areas, and 3) individuals exposed to one chemical of toxicologic interest were also likely to be exposed to other similarly toxic materials. The use of both work area and chemical-specific exposure measures is recommended, as each may be helpful in addressing etiologic questions regarding complex work environments.

Population based mortality surveillance in carbon products manufacturing plants

The utility of a population based, corporate wide mortality surveillance system was evaluated after a 10 year observation period of one of the company's divisions. The subject population, 2219 white male, long term employees from Union Carbide Corporation's carbon based electrode and specialty products operations, was followed up for mortality from 1974 to 1983. External comparisons with the United States male population were supplemented with internal comparisons among subgroups of the study population, defined by broad job categories and time related variables, adjusting for important correlates of the healthy worker effect. Significant deficits of deaths were observed for all causes and the major non-cancer causes of death. The numbers of deaths due to malignant neoplasms and respiratory cancer were less than, but not statistically different from, expected. There was a non-significant excess of deaths from lymphopoietic cancer, occurring predominantly among salaried employees. When specific locations were examined, operations with potential exposure to coal tar products exhibited a mortality pattern similar to that of the total cohort. The risk for lung cancer was significantly raised (five observed, 1.4 expected) in one small, but older, location which did not involve coal tar products during the period of employment of these individuals, but which historically used asbestos materials for several unique applications. Although these findings are limited by small numbers and a short observation period, the population based surveillance strategy has provided valuable information regarding the mortality experience of the population, directions for future research, and the allocation of epidemiological resources.

Cause-specific mortality among male chemical workers

Cause specific mortality was surveyed among 37,682 male employees with three or more days of service between 1940 and 1982 at the Midland or Bay City, Michigan, locations of Dow Chemical USA. Vital status was ascertained through 1982 for 97.5% of the cohort members, and death certificates were obtained for 97.1% of the 7,751 decedents. Comparisons of observed mortality with expected levels based on any of three general population groups (US, Michigan, or seven local counties) consistently demonstrated lower mortality in the cohort from each of the major causes of death, including total malignant neoplasms. Unique among hourly employees was significant excess mortality in the categories of cancer of other lymphatic tissue, and motor vehicle accidents, and both hourly and salaried nonexempt employees experienced significantly higher mortality from other and ill-defined cancers. The influence of duration of employment and age at and period of hire were explored with the Mantel-Haenszel method as adapted for a cohort study. Results were evaluated both including and excluding the mortality experience of subsets of employees with past exposure to known human carcinogens (arsenic, asbestos, bis-chloromethyl ether, benzene, organic dyes, and vinyl chloride). The use of the general mortality survey in monitoring whether or not there are major health problems among the employees and in setting research priorities is emphasized.