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Biomedical subjects

R R Cook

Publications and source records attributed to R R Cook.

At least 55 records · Page 3Linked to original sources
PubMed1989

Morbidity among employees engaged in the manufacture or formulation of chlorpyrifos.

The prevalence of selected illnesses and symptoms during 1977-85 was compared between 175 employees potentially exposed to the organophosphate insecticide chlorpyrifos and 335 matched controls with no history of exposure to organophosphates. Subjects were subdivided into three exposure intensity groups on the basis of job title and air monitoring data for dose response testing. This classification scheme was shown roughly to correlate with plasma cholinesterase inhibition in the workers. No statistically significant differences in illness or prevalence of symptoms were observed between the exposed and unexposed groups or among the three exposure subgroups. Potentially exposed employees did report symptoms of dizziness and of malaise and fatigue relatively more often than subjects from the comparison group; however, further analyses by exposure level, process area, or time did not support a relation with exposure. No cases of peripheral neuropathy were seen among the exposed workers. Although the sample size was small and the statistical power limited, the cumulative exposures likely to have been experienced by this workforce exceed those to be expected for individuals using the product as recommended. The absence of exposure related adverse effects, including neurological impairment, is reassuring.

Chemical Industry↗
PubMed1989

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.

Cohort Studies↗
PubMed1988

Use of a population-based tumor registry to estimate cancer incidence among a cohort of chemical workers.

There have been many studies conducted of mortality in occupational cohorts, but few of cancer incidence. Two major facilities of the Western Division of Dow Chemical USA are located fortuitously within an area covered by the population-based California Tumor Registry, which allowed linkage of records to identify incident cancers among 1,403 male workers. Using adjusted county rates for comparison, 49 new cancers were observed in the cohort from 1969 through 1983, whereas 63.0 were expected (standardized incidence ratio = 78, 95% confidence limits = 53 to 103). Nonsignificant excesses were noted for several cancer groups among some categories of workers; however, there was no predominant tumor type within the groups. The successful completion of this collaborative project suggests that using population-based tumor registries for surveillance of occupational cohorts is feasible.

Adult↗
PubMed1988

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.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1987

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.

Accidents, Occupational↗
PubMed1987

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.

Adult↗
PubMed1987

Dietary vitamin A and lung cancer: results of a case-control study among chemical workers.

A nested case-control study conducted among a cohort of chemical manufacturing employees provided an opportunity to test the hypothesis that lung cancer risk is inversely related to dietary intake of vitamin A. Eligible for study were 308 former male employees who had died of lung cancer between 1940 and 1980. Two control groups, one a decedent and the other a "living" series, were individually matched to the cases one-for-one. Interviews were completed with 734 subjects or their next-of-kin and included a food frequency list. A vitamin A index was developed for each subject based on the frequency of consumption of 29 food items. After adjustment for a number of potentially confounding variables (e.g., smoking, educational level, and use of vitamin supplements), there was evidence that vitamin A intake was inversely associated with lung cancer risk. The effect was most pronounced in the comparisons with the "living" controls and appeared strongest among cigarette smokers. Subjects in the lowest tertile of vitamin A intake had approximately twice the risk of lung cancer as those in the highest. Analyses of an index of carotenoids and of individual food items suggested that plant sources of vitamin A may play a more important role in producing the effect than do animal sources.

Adult↗
PubMed1987

Cohort mortality study of chemical workers with potential exposure to the higher chlorinated dioxins.

This cohort study evaluated mortality patterns, 1940 through 1982, of 2,192 chemical workers who, having engaged in the manufacture of higher chlorinated phenols and derivative products, had potential occupational exposures to chlorinated dioxins. Relative to United States white male mortality experience, there were no statistically significant deviations from expected for the following categories: all causes, total malignant neoplasms, or specific malignancies of particular interest: stomach cancer, liver cancer, connective and other soft-tissue cancer, the lymphomas, or nasal and nasopharyngeal cancer. For the cirrhosis of the liver category, internal comparisons demonstrated increasing trends associated with duration of employment in the Chlorophenol Production and Finishing areas; but available evidence suggests this finding was related to alcohol abuse. The study does not support a causal association between chronic human disease as measured by mortality and exposures to the higher chlorinated phenols, derivative products, or their unwanted contaminants, the chlorinated dioxins.

2,4,5-Trichlorophenoxyacetic Acid↗
PubMed1986

Nested case-control study of lung cancer among chemical workers.

A recent cohort mortality study of 19,608 male employees of a major Texas chemical production facility had suggested that they might be at higher risk of lung cancer compared with the male population of the United States or Texas but not with the male population of the five-county area in which they reside. An occupational exposure was a possible explanation for this pattern, and a nested case-control study was undertaken of the 308 lung cancer deaths observed between 1940 and 1981. Two control groups, one a decedent and the other a "living" series, were individually matched to cases one-for-one. Interviews were conducted with subjects or their next of kin to collect information on smoking and other potential confounders. These data were combined with employee work history records and industrial hygiene data to form the basis of the analyses. Traditional stratification methods and conditional logistic regression were employed to examine for effect modification and to control confounding. Statistically significant, positive and negative associations were found for assignment to several work areas within the facility. Suggestive associations were observed for exposure to sulfur dioxide and heat. These and additional associations are discussed relative to evidence from other studies.

Adult↗
PubMed1986

An update of mortality among chemical workers exposed to benzene.

Mortality was updated to the end of 1982 for 594 employees exposed to benzene who had been studied previously and for an additional 362 exposed workers not studied previously. Cause specific mortality comparisons were made using United States white male, age, and calendar year adjusted rates. Total mortality was observed to have been significantly below expectation, and this was particularly evident for deaths from accidental causes. Mortality from skin cancer was significantly raised, although there were no unusual or common characteristics among the affected individuals which would suggest a link with exposure to benzene. A non-significant excess of total deaths from leukaemia was noted based on four observed cases; however, all four were myelogenous leukaemias and this represented a significant excess in that subcategory. These and other deaths of possible interest are reviewed in detail. Analyses by work area, duration of exposure, and cumulative dose index did not show patterns suggestive of a causal association between exposure to benzene and any particular cause of death.

Adult↗
PubMed1985

A case-control study of renal cancer mortality at a Texas chemical plant.

An in-plant case-control study of 26 renal cancer deaths was conducted to determine whether an occupational exposure may be related to an apparent increase in mortality from this disease observed among a sample of employees at a multiple process chemical production facility. None was found that explained the excess. Elevated odds ratios were identified for employment in the cell maintenance area of chlorine production and with those presumptive exposures considered to occur in this job, asbestos and caustic, but not chlorine. While an association between renal cancer and asbestos has been previously reported, an association with caustic, per se, is not consistent with prior observations made by others. Diminished risk estimates were observed for employment in magnesium production and for exposures in this process to sulfur dioxide and heat. Both the increased and decreased risks, while statistically significant, are based on small numbers of exposed subjects and may be spurious owing to the problem of multiple comparisons.

Adult↗
PubMed1985

Mortality among a large cohort of chemical manufacturing employees.

Cause-specific mortality was surveyed among 19,608 male employees with 1 or more years of service between 1940 and 1980 at the Texas Operations of Dow Chemical U.S.A. Vital status was ascertained through 1980 for 97.3% of the cohort members, and death certificates were obtained for 96.4% of the 3,444 decedents. Mortality risks were found to vary, depending upon which of 3 population groups (United States, Texas, and local counties) was used for comparison, although significantly fewer than expected deaths from all causes was a common finding due to significant deficits in diabetes, diseases of the circulatory system, and cirrhosis of the liver. Significantly more deaths were from ill-defined conditions and cancers of unspecified sites. Lung cancer was significantly elevated in comparisons with the incidences in the United States and Texas, but not in comparison with those in the local counties. The influence of age at hire, period of hire, duration of employment, interval since entry into cohort, employment status, and two measures of social class--educational level and job category--were explored with the use of the Mantel-Haenszel method as adapted for a cohort study. Findings from these analyses are discussed in relation to the observations of other investigators and in the context of the possible impact of these findings on future studies of this work force.

Chemical Industry↗