Half-century of cause-specific mortality experience of chemical manufacturing employees.

Cause-specific mortality was surveyed among 23,180 male (580,000 person-years) and 3,860 female (86,898 person-years) employees with 1 or more years of service from 1940 through 1989 at a large chemical plant. Vital status was ascertained for 99.1% of the males (n = 5,658 deaths) and 98.6% of the females (n = 355 deaths). Comparisons of observed mortality with expected levels based on any of three population comparisons (United States, Texas, or five local counties) showed lower mortality for all causes of death, diseases of the circulatory system, diabetes mellitus, and cirrhosis of the liver. There was an increased risk for lung cancer mortality among male operations employees when compared to the U.S. and Texas populations but not to the local five-county region. Additional evidence suggests this increase was primarily attributable to cigarette smoking. Male operations employees also had an elevated, although not statistically significant, risk for kidney cancer. Prior research had shown an association with work in the cell maintenance area of chlorine production. As a result of a high prevalence of deaths certified by justices of the peace, a mortality excess was observed of cancer of other and unspecified sites and symptoms, senility, and ill-defined conditions. Although specific chemical exposures were not studied, the generally favorable mortality experience suggests that major hazards are unlikely.

Preliminary evaluation of an employer-sponsored mammography screening program.

Recognizing the importance of early detection of breast cancer, the Dow Chemical Company initiated a breast cancer awareness program in 1988. Evaluation of operational aspects of mammography screening component revealed that about half (53%) of 1186 eligible women in the evaluation cohort took part, although participation was three times higher for active than for retired employees. Eleven per cent of participants were considered to have "positive" screens, ie, had roentgenogram films with suspicious areas, and at least 82% of these women had follow-up medical services within 1 year of screening, as determined by a review of group insurance claims records. Two women with positive mammograms were subsequently diagnosed and treated for breast cancer within 2 months of screening. None of the women with negative mammograms developed breast cancer in the subsequent year. The suitability of group insurance data resources for responding to health care delivery questions is discussed.

A comparison of cause-specific mortality among participants and nonparticipants in a work-site medical surveillance program.

Nonparticipants in general population health surveys have been found to be less healthy than participants, but data on nonparticipants in work-site health surveys have been more scarce. We compared cause-specific mortality among 11,156 male employees of The Dow Chemical Company who participated in at least one work-site health examination between 1967 and 1978 with 6915 employees who did not participate. The nonparticipants experienced higher mortality rates for nearly every cause of death examined but particularly from smoking and alcohol-abuse related diseases. This was especially true during the first 5 years of follow-up, suggesting that some employees do not participate because they are already ill. These findings have important implications for the use of examination data for both primary and secondary disease prevention purposes, and these are discussed.

Liver and biliary tract cancer among chemical workers.

A recent cohort mortality study of male, hourly wage employees of a large Michigan chemical production and research facility had found a greater than expected number of deaths coded to liver and biliary tract cancer. In response, an additional investigation was then undertaken of the 44 liver and biliary tract cancer deaths observed between 1940 and 1982. A random sample (N = 1,888) of subjects was selected from the total cohort (N = 21,437) to serve as referents. Company work history records were used to classify cases and referents by work area assignment and potential for exposure to 11 selected chemical agents which have been shown to produce cancer of the liver or biliary passages in experimental animals. Statistically significant associations in both positive and negative directions were found for several work areas within the facility. A suggestive association was found for vinyl chloride monomer, based on five cases with presumed exposure.

Update of mortality among chemical workers with potential exposure to the higher chlorinated dioxins.

This study provided 2 additional years of follow-up through 1984 for a previously studied cohort of 2192 employees potentially exposed to chlorinated dioxins. A separate analysis was done of the subgroup of 323 workers who had chloracne. No clear evidence was found for a causal association between any cause of death and potential occupational exposures to the higher chlorinated phenols, derivative products, or the chlorinated dioxins. Particular focus was directed at mortality from cancers of the stomach, liver, connective and other soft tissue, nasal and nasopharynx, and the lymphomas. Analyses by various indices of exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin and hexa- to octachlorinated dioxins did not show deaths from these cancers to have been disproportionately distributed among the workers considered to have had the highest exposures.

Mortality comparisons of chemical workers hired before, during, and after World War II (1941-1945).

Cause-specific mortality was evaluated by period of hire for 37,682 male chemical workers in order to test the hypothesis that employees hired during World War II (1941-1945) were at increased risk for selected causes of death. One recent study of refinery workers reported that those hired during the war years had experienced greater mortality from external causes (accidents, homicides, and suicides), alcoholism, and cancers of several sites relative to employees hired before or after the war. In the present study, employees were divided into three period-of-hire subcohorts: prior to 1941, 1941-1945 (World War II), and 1946 and after. Comparison of observed mortality among these subcohorts through 1982 was made with expected levels based on age- and calendar year-specific U.S. white male rats. Neither hourly nor salaried employees hired during the war showed evidence of higher mortality from homicide, suicide, alcoholism, or any of the selected cancer types suggested from the refinery study. Hourly, but not salaried, war years new hires experienced excessive mortality from only those accidents involving motor vehicles. Possible reasons for the discrepant findings between this and the earlier study of refinery workers are discussed, with methodological differences being dismissed.

Cause specific mortality among employees engaged in the manufacture, formulation, or packaging of 2,4-dichlorophenoxyacetic acid and related salts.

Mortality is reported to the end of 1982 for 878 chemical workers potentially exposed to 2,4-dichlorophenoxyacetic acid (2,4-D) at any time between 1945 and 1983. Observed mortality was compared with expected levels based on adjusted rates for United States white men and for other male employees from this manufacturing location who were not exposed to 2,4-D. Because of a recently reported increased incidence of astrocytomas in male rats fed the highest dose level of 2,4-D, special attention was given to deaths from brain neoplasms in the cohort. None was observed. The absence of an increased risk of brain cancer in people exposed to 2,4-D is supported by studies of other exposed populations and those studies are briefly reviewed. Moreover, in the present study, analyses by production area, duration of exposure, and cumulative dose showed no patterns suggestive of a causal association between 2,4-D exposure and any other particular cause of death.

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.

Mortality among female employees of a chemical company.

There have been few mortality studies conducted on working women despite their increasing presence in the work environment. This paper presents the findings of a cohort mortality study of 10,839 female employees with three or more days of service between 1940 and 1982 at the Midland or Bay City, Michigan, locations of the Dow Chemical Company. The cohort included substantial numbers of production and research personnel but was primarily comprised of clerical and office workers. Vital status was ascertained through 1982 for 89.4 percent of the cohort members, and death certificates were obtained for 94.0 percent of the 467 decedents. Comparisons of observed mortality with expected levels based on mortality rates for the U.S., Michigan, and a local 7-county area revealed consistently lower mortality in the cohort from the major causes of death, indicating a strong "healthy worker effect." Mortality from cancer of the cervix was significantly below expected levels, especially among women who were hired before 25 years of age. This observation, when combined with a nonsignificant excess of breast cancer, suggests a different distribution of maritally and sexually related risk factors between working and general populations of women. This and other findings are discussed relative to methodologic problems likely to accompany studies of working women.