PubMed Health⌕ Search

Biomedical subjects

R R Cook

Publications and source records attributed to R R Cook.

At least 37 records · Page 2Linked to original sources
PubMed1989

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 of Death↗
PubMed1989

Phenoxy herbicides and cancer: insufficient epidemiologic evidence for a causal relationship.

The question as to whether or not any or all of the phenoxy herbicides are carcinogenic to humans continues to be evaluated. We review the evidence available from the retrospective cohort and case-control epidemiology studies. Graphs of the individual probability densities for the odds ratios from the eight case-control studies of soft-tissue sarcoma, Hodgkin's disease, or non-Hodgkin's lymphoma demonstrate gross inconsistencies which are not likely to be attributable to chance. Early studies, conducted in Sweden, had indicated strong associations, but subsequent work from New Zealand and the United States has failed to substantiate those findings. The reasons for the discordant results may relate more to methodologic problems in the earlier studies than to qualitative or quantitative differences in the exposures of the underlying populations. The retrospective cohort studies offer the advantage of having focused on occupational groups believed to have had the highest exposures, although they have been criticized as being individually too small to assess the risks of the rarer forms of cancer. Consideration of the combined cohort studies of workers exposed to the phenoxy herbicides per se provides little or no evidence of carcinogenicity. Thus, the total weight of evidence currently available does not support a conclusion that the phenoxy herbicides present a carcinogenic hazard to humans.

2,4,5-Trichlorophenoxyacetic Acid↗
PubMed1989

The role of "negative" epidemiology data in the evaluation of risk.

The identification and quantification of risk is a complex process that depends upon a variety of different disciplines. All contribute, but none provides a complete and comprehensive perspective. In the past, emphasis has been placed upon the limitations of each individually. Toxicology, for example, is plagued by low predictive value positive; epidemiology, by qualitative measures of exposure. Focusing instead upon the contributions of each to the whole, and the contributions of all of the data--both "positive" and "nonpositive"--a better understanding of potential hazards can be achieved. Examples are provided for styrene and phenoxy herbicides.

Animals↗
PubMed1989

Incidence of chloracne among chemical workers potentially exposed to chlorinated dioxins.

Company medical charts were reviewed for 2192 chemical workers who were potentially exposed to chlorinated dioxins during 1940 to 1982 to determine whether they were ever diagnosed as having chloracne. Nearly 16% of the 2072 workers with medical records were found to have been so affected. The incidence of chloracne was noted to have been highest among the youngest workers, and among those who worked in the production of chlorinated phenols rather than with products derived from those materials. Chloracne incidence was found to increase with several measures of intensity and cumulative dose of tetra- and hexa- to octachlorinated dioxins, but these analyses were hampered somewhat by the limitations of both the exposure and medical outcome data.

Acne Vulgaris↗
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↗