William G. Tankersley

A mortality study of men exposed to elemental mercury

A cohort of 2,133 white males who were exposed to elemental mercury vapors between 1953 and 1963 was followed up through the end of 1978. Death certificates were obtained for 371 of the 378 workers who were reported by the Social Security Administration to be deceased. The mortality experience of this group was compared with the age-adjusted mortality experience of the U.S. white male population. Mortality has not been studied previously in assessing the long-term health effects of mercury exposure. Standardized mortality ratios (SMRs) were calculated for a comparable unexposed worker population to determine the mortality patterns among workers at the same plant who were not involved in the mercury process. Statistically significant excesses of deaths from cancer of the lung (SMR = 1.34; 71 observed, 52.9 expected) and cancer of the brain and other CNS tissues (SMR = 2.30; 13 observed, 5.65 expected) were observed among the plant workers who were not involved in the mercury process. An excess of deaths from cancer of the lung was also observed among the mercury workers (SMR = 1.34; 42 observed, 31.36 expected), although the elevation of this SMR was not statistically significant. Since excesses of lung cancer were evident in both groups of workers, it is unlikely that they are related to the mercury exposure and more probable that they are due to some other factor present in the plant or to some life-style factor prevalent among the plant workers.(ABSTRACT TRUNCATED AT 250 WORDS)

Collection, Validation, and Treatment of Data for a Mortality Study of Nuclear Industry Workers

Abstract To investigate the long-term health effects of protracted occupational exposure to low levels of ionizing radiation, a combined facility mortality study was initiated for 118,588 workers hired between 1942 and 1982 by three Department of Energy facilities in Oak Ridge, Tennessee. The primary objectives of the study were: (1) to evaluate and compare the mortality experience of separate subcohorts delineated by facility of employment, and (2) to conduct detailed dose-response analyses of the combined facilities subcohort having potential for external radiation exposure. Presented here are issues involving validation and treatment of data for study members, and characteristics of their radiation exposure. To verify data accuracy a stratified random sample was chosen, and original source documents containing demographic and radiation exposure data were reviewed. Health physicists investigated monitoring policies and practices in place at each facility over the 42 years of follow-up (1943 to 1984) bef...

Exposure and genetics increase risk of beryllium sensitisation and chronic beryllium disease in the nuclear weapons industry

Objectives Beryllium sensitisation (BeS) and chronic beryllium disease (CBD) are caused by exposure to beryllium with susceptibility affected by at least one well-studied genetic host factor, a glutamic acid residue at position 69 (E69) of the HLA-DPβ chain (DPβE69). However, the nature of the relationship between exposure and carriage of the DPβE69 genotype has not been well studied. The goal of this study was to determine the relationship between DPβE69 and exposure in BeS and CBD. Methods Current and former workers (n=181) from a US nuclear weapons production facility, the Y-12 National Security Complex (Oak Ridge, Tennessee, USA), were enrolled in a case–control study including 35 individuals with BeS and 19 with CBD. HLA-DPB1 genotypes were determined by PCR-SSP. Beryllium exposures were assessed through worker interviews and industrial hygiene assessment of work tasks. Results After removing the confounding effect of potential beryllium exposure at another facility, multivariate models showed a sixfold (OR 6.06, 95% CI 1.96 to 18.7) increased odds for BeS and CBD combined among DPβE69 carriers and a fourfold (OR 3.98, 95% CI 1.43 to 11.0) increased odds for those exposed over an assigned lifetime-weighted average exposure of 0.1 μg/m3. Those with both risk factors had higher increased odds (OR 24.1, 95% CI 4.77 to 122). Conclusion DPβE69 carriage and high exposure to beryllium appear to contribute individually to the development of BeS and CBD. Among workers at a beryllium-using facility, the magnitude of risk associated with either elevated beryllium exposure or carriage of DPβE69 alone appears to be similar.

Mortality among titanium dioxide workers at three DuPont plants.

Objective: To evaluate the mortality among workers employed at three titanium dioxide plants in the United States. Methods: We expanded and updated a cohort employed at titanium dioxide plants. Cause-specific standardized mortality ratios (SMRs) were calculated combined and stratified by plant for workers employed at least 6 months between 1935 and 2005. Results: No indications of excess mortality from any cause were found. All causes SMR increased with length of plant operation as did most cause-specific SMRs. With lung, the target organ of interest, no increases in malignant or nonmalignant respiratory disease were observed. Conclusions: The mortality rates are comparable with the general US population. Increasing SMRs with length of plant operation is indicative of waning healthy worker effect with time since first employment. The results are comparable with other titanium dioxide cohort studies.

Occupational exposure and mortality among workers at three titanium dioxide plants

BACKGROUND A cohort of 3,607 workers employed in three DuPont titanium dioxide production facilities was followed from 1935 through 2006. METHODS Combined and plant-specific cohort mortality was compared with the overall US population and other DuPont employees. The relationships between selected causes of death and annual cumulative exposures to titanium dioxide and chloride were investigated using Poisson regression methods to examine trends with increasing exposure. RESULTS Among the 833 deaths, no causes of deaths were statistically significantly elevated either overall or plant-specific when compared to the US population. Compared to DuPont workers, statistically significantly elevated SMRs for all causes, all cancers, and lung cancers were found driven by the workers at the oldest plant. Comparing increasing exposure groups to the lowest group, disease risk did not increase with exposure. CONCLUSIONS There was no indication of a positive association between occupational exposure and death from all causes, all cancers, lung cancers, non-malignant respiratory disease, or all heart disease.

Task- and time-dependent weighting factors in a retrospective exposure assessment of chemical laboratory workers.

A chemical exposure assessment was conducted for a cohort mortality study of 6157 chemical laboratory workers employed between 1943 and 1998 at four Department of Energy sites in Oak Ridge, Tennessee, and Aiken, South Carolina. Previous studies of chemical laboratory workers have included members within professional societies where exposure assessment was either limited or not feasible, or chemical processing employees where laboratory and production workers were combined. Because sufficient industrial hygiene records were unavailable for all four sites, weighted duration of employment was used as a surrogate for the magnitude of exposure. Potential exposure indices were calculated for each worker using number of days employed and weighting factors for frequency of contact and year of employment. A total of 591 unique laboratory job titles indicative of a chemical laboratory worker were collapsed into 18 general job title categories. Through discussions with current and retired workers, along with examination of historical organizational charts and job descriptions, the percentage of time with activities involving the direct handling of chemicals in the laboratory was estimated for each job title category. Scaled weighting factors of 1, 0.6, 0.3, and 0.05 were assigned to the job title categories representing 100%, 60%, 30%, and 5% of daily activities handling chemicals, respectively. Based on limited industrial hygiene monitoring data, personal radiation monitoring records, and professional judgment, weighting factors that declined 4% annually were applied to each year to account for improvements in laboratory technique, advancements in instrumentation, improvement in engineering controls, and increased safety awareness through time. The study cohort was separated into three categories of chemical exposures based on department level information: (1) inorganic, (2) mixed inorganic and organic, and (3) unknown. Potential exposure indices ranged from 0.15 to 6824.5 with a median value of 377.5 and a mean equal to 884.2. This exposure assessment method is useful for epidemiologic analyses when quantitative exposure data are absent or insufficient.

ESTIMATION OF RADIATION DOSES FOR WORKERS WITHOUT MONITORING DATA FOR RETROSPECTIVE EPIDEMIOLOGIC STUDIES

Dosimetry data are required for many epidemiologic studies of radiation workers. For several reasons, these data may not be available for some workers for some periods of time. An estimate of a workers dose for such a time period can be made using data from nearby time periods for the worker or using data obtained for other workers during the same time period. This paper reports the results of an evaluation of a procedure for estimating external doses for workers included in retrospective epidemiologic studies. This evaluation was conducted using data for workers who had recorded doses for each year in a 5-y period. The dose for the middle year of the 5-y period was treated as unavailable and the dose was estimated several ways. These estimates were compared with the recorded dose. It was observed that averaging a workers dose data for the years preceding and following a year for which data hypothetically were not available most often yielded the best estimate of the dose. At one facility studied, the use of nearby data for the same worker was a more reliable estimate for a dose than was the department or facility median or mean dose. However, at another facility, use of the department median or mean dose produced a more accurate estimate than did nearby data for the worker. These results indicate that a single procedure for estimating doses is not best for all facilities, and it is recommended that a test of the type reported in this paper be performed before a decision is made on how to estimate doses. The use of department medians or means to estimate doses consistently produced better estimates than were obtained using facility medians or means.

Induction and Isolation of a Minicell-Producing Strain of Salmonella typhimurium

Summary A mutant of S. typhimurium which produces small spherical anucleate bodies (minicells) was induced and isolated after treatment of a normal strain of S. typhimurium with increasing amounts of triethylenemelamine (TEM). No differences were observed in growth characteristics or colonial morphology between the minicell-producing strain and the normal strain of S. typhimurium. The minicells were shown to be approximately onetenth the size of normal cells of S. typhimurium and were easily isolated from the larger parent cells by a combination of differential and density-gradient centrifugations. Purified minicell preparations contained about 0.007 the amount of DNA per cell as normal cells. They utilized glucose linearly with time, and were serologically indistinguishable from normal cells.

Lung dose estimates from air sampling and bioassay data - a comparison

Occupational monitoring data are typically in the form of air samples or biological samples. Air samples are more frequently available and often have been used to characterize personnel exposure in epidemiological studies. Air samples that are not specific to individual employees are easier and cheaper to procure than biological samples such as urinalyses. However, the correlation between concurrent air samples and urinalyses has not always been found to be strong. The purpose of this paper is to compare internal radiation doses for uranium workers estimated from air sample results with those estimated from urine sample results. The comparison was made on results associated with individuals who worked in a uranium processing and fabrication facility between 1950 and 1956. Independent lung dose estimates were made for individuals for whom both types of data were available for periods of 300-365 d. Plots of the data and statistical analyses failed to show evidence of correlation of any practical significance between the data generated by the two methods. A number of unquantifiable variables were enumerated for both types of estimates. It is concluded that within this study (1) only minimal correlation was demonstrable between lung doses based on air monitoring and doses based on urinalysis data because of the number of such variables affecting the measurements; and (2) general air data would not be the most useful measure of exposure upon which to base lung dose estimates.