Assessment of clinical, metabolic, dietary, and occupational correlations with serum polychlorinated biphenyl levels among employees at an electrical capacitor manufacturing plant.

In order to assess the extent of polychlorinated biphenyl (PCB) exposure and potential health effects, a clinical-epidemiologic survey was initiated among 205 workers at a capacitor manufacturing plant. The geometric mean serum PCB level for workers was 18.2 ppb (SD 2.88), with a range of 0 to 424 ppb. Multiple regression analysis found duration of employment, cumulative occupational exposure, cumulative fish consumption, and cholesterol level to be significant predictors of log serum PCB levels. Of these predictors, duration of employment and cumulative occupational exposure were the strongest contributors to the regression model, indicating the dual importance of opportunity for dermal contact and respiratory exposure level in contributing to workers' serum PCB levels.

An analysis of mortality follow-up through the National Death Index for a cohort of refinery and petrochemical workers.

Along with our submission to the National Death Index (NDI) of a cohort of more than 23,000 petrochemical and refinery workers, we included 1,449 known U.S. deaths to determine the completeness of death ascertainment through the NDI. A number of factors that may affect follow-up were examined including sex, race, age and reporting area. Overall, NDI detected 97.1% of known deaths. Follow-up was slightly better for males (97.2%) than for females (92.0%) and was significantly better for whites (97.6%) than for nonwhites (92.0%). Analyses by reporting area showed very complete follow-up from all locations (93.4%-100%) except for the New York City area (71.4%). These findings indicate that NDI is an extremely useful source for vital status follow-up, though follow-up may be somewhat less complete for certain subgroups of an occupational study cohort.

A retrospective mortality study of workers in three major U.S. refineries and chemical plants. Part II: Internal comparisons by geographic site, occupation, and smoking history.

A cohort of 21,698 U.S. refinery and chemical plant workers was observed for eight years to determine if there were interplant or other variations in causes of mortality. Plant populations in three geographic locations were combined to develop an internal standard for comparing subgroups within the total cohort. At no one geographic site were consistently different rates for all major causes of death observed. The adjusted mortality rates for potentially exposed workers were slightly greater than those for nonexposed workers for most causes examined. Smokers incurred a higher risk of mortality from many causes of death when compared with nonsmokers, regardless of occupational category. After controlling for smoking, there remained a slight excess in mortality for potentially exposed as compared with nonexposed workers.

A retrospective mortality study of workers in three major U.S. refineries and chemical plants. Part 1: Comparisons with U.S. population.

A dynamic retrospective cohort study was performed to examine the mortality experience of 21,698 workers at Exxon's refineries and chemical plants in Baton Rouge, La.; Baytown, Tex.; and Bayway/Bayonne, N.J. Included were 15,437 regular employees who worked at least one month during the period Jan. 1, 1970, through Dec. 31, 1977, and 6,261 retirees who were alive as of Jan. 1, 1970. There were 137,702 person-years of observation. Mortality in this total study population was generally lower than that of the U.S. population. Study follow-up was complete for 98.7% of the study population. The standardized mortality ratio for the 3,198 deaths was 91, while that for deaths from all cancers (N = 666) was 94. Certain slightly elevated disease-specific mortality ratios, although not statistically significant, could be of biological importance and merit further review.

Laryngeal cancer and occupational exposure to sulfuric acid.

Workers on an ethanol unit which used sulfuric acid in strong concentrations at a large refinery and chemical plant in Baton Rouge, Louisiana were reported, in 1979, at excess risk for upper respiratory cancer. The carcinogen implicated by indirect evidence was diethyl sulfate. However, with the continued use of sulfuric acid in the same plant, and with additional cases not attributable to the ethanol process, the hypothesis of an association between sulfuric acid exposure and upper respiratory cancer was tested. Each of 50 confirmed cases of upper respiratory cancer diagnosed between 1944 and 1980, was matched to at least three controls on sex, race, age, date of initial employment, and duration of employment. Thirty-four of the 50 cases were laryngeal cancers. Data were obtained from existing plant records. Retrospective estimates of exposure were made without regard to case or control status. Findings from conditional logistic regression techniques were supported by other statistical methods. Among workers classified as potentially highly exposed, four-fold relative risks for all upper respiratory cancer sites combined were exceeded by the relative risk for laryngeal cancer specifically. Exposure-response and consistency across various comparisons after controlling statistically for tobacco-use, alcoholism and other previously implicated risk factors, suggest increased cancer risk with higher exposure.

Epidemiologic study of refinery and chemical plant workers.

A dynamic retrospective cohort study was performed to examine the mortality experience of workers at Exxon's Baton Rouge, La refinery an chemical plant. Included were 8,666 regular employees who worked at least one month during the period Jan 1, 1970 through Dec 31, 1977, and retirees who were alive as of Jan 1, 1970. Mortality from all causes of death was lower than expected when compared with that of the U.S. population of similar age, sex, and race. Analyses of mortality by specific site of cancer revealed elevated standardized mortality ratios SMRs) for cancer of the kidney, testis, brain/central nervous system, pancreas, and lymphopoietic sites; none of these elevations was statistically significant. Because of the higher than average mortality from cancer of the pancreas in some Louisiana parishes and the observation that one additional death from cancer of the pancreas in this study would have resulted in a statistically significant SMR at the 95% confidence level, some emphasis was placed on this finding. No evidence was found to link cancer of the pancreas to a specific occupational group. An examination of mortality by occupational class revealed some elevated SMRs for further study.

Brain cancer: issues and dilemmas.

A cohort study covering the eight year period, 1970-1977, identified eight deaths attributed to brain cancer among employees at a refinery/chemical plant. Five of the cases were primary brain cancers and three were either metastatic from another site or the site was undetermined. A ninth case of brain tumor unspecified was identified. Five primary brain cancers would have been expected, based on national statistics. Some issues and dilemmas related to such a cohort study were discussed.

An association of upper respiratory cancer with exposure to diethyl sulfate.

A morbidity and mortality study of workers at an alcohol manufacturing plant which included several weak acid isopropyl alcohol units and a strong acid ethanol unit is described. An excess mortality of upper respiratory cancer was found and associated with work on the strong acid ethanol unit. The strong acid ethanol process used resulted in high concentrations of diethyl sulfate, which has been shown to be carcinogenic in animals, and the unit, which closed on 1975, had significant opportunities for worker exposure to diethyl sulfate. These facts, plus previous reports of excess upper respiratory cancer on strong acid isopropyl alcohol units with similarly high concentrations of the animal carcinogen diisopropyl sulfate, lead to the tentative conclusion that diethyl sulfate was primarily responsible for the ethanol unit cancer cases. In the modern weak acid isopropyl alcohol plants, where only trace amounts of diisopropyl sulfate are present and exposures are much lower, the problems found on the old strong acid units do not exist.

Cancer mortality in oil refinery workers.

The cancer mortality experience from 1964 to 1973 of employees of the Imperial Oil Limited was examined in a cohort study. Employees in jobs which exposed them on a daily basis to crude petroleum or its products, compared with nonexposed employees, were found to have more than three times the risk of esophageal and stomach cancer and about twice the risk of lung cancer. In the exposed group, increasing risks of both cancers occurred with increasing duration of employment. In the absence of more complete information on the similarity of the exposed and nonexposed employees, these results cannot be ascribed with certainty to a carcinogenic effect of petroleum. However, there was no other clear explanation for the results, and further study is required. When refinery workers were compared with nonrefinery workers without consideration of exposure to petroleum in either group, the refinery workers were found to have twice the risk of cancer of the intestines (including rectum) and other digestive organs. No relationship with duration of employment was evident. Although the increased intestinal cancer mortality in the refinery workers was not consistent, bias was not an obvious explanation for the observed relationship. Therefore, the presence on a refinery site of a carcinogen other than petroleum has not been ruled out, and further study is urged.