David F. Utterback

An experimental design approach to retrospective exposure assessment.

There are several methods currently in use for retrospective estimation of quantitative exposure levels in occupational and environmental epidemiologic studies. The most popular is a job-exposure matrix approach using a combination of existing data and professional judgment. Another method is the use of statistical models based on available exposure data. The authors present an alternative approach using an experimental design in which several factors thought to affect exposure levels are identified and set at specific levels in a cross-classified design. This approach was used to estimate historical exposures to formaldehyde in a mortality study of embalmers. Exposures were estimated as a function of solution concentration, air exchange rate, and autopsied versus intact body. There were 12 combinations involving these 3 factors and a total of 25 embalming procedures (approximately 2 replicates of each combination) performed at a college of mortuary science. In addition to these design factors several covariates such as temperature, humidity, and the occurrence of spills were considered in an analysis of covariance statistical model. The results of the model prediction were validated against published measurements, and field samples were taken in several funeral homes. The overall accuracy of the model predictions was comparable to the variation found in replicate measurements of identical embalming procedures.

Study Design for Assessing Exposures of Embalmers for a Case-Control Study. Part I. Monitoring Results

Abstract Epidemiologic studies of embalmers and funeral directors have found excess risks of mortality due to leukemia and brain cancer. To investigate specific occupational exposures that might account for these associations, a case-control study of these diseases among embalmers is under way. To quantify exposure levels for this study, a series of embalmings was performed using an experimental design to determine the effect of certain work parameters on the concentration of airborne contaminants. Personal exposures and area concentrations of formaldehyde, methanol, phenol, and particulates were measured during 25 embalmings while controlling the level of ventilation, the concentration of the embalming solution, and the type of case (autopsy or intact body). In addition, bischloromethyl ether (BCME) and selected microorganisms (total, fungi, and bacteria) were measured during a few embalmings. Personal formaldehyde exposures ranged from 0.31 to 8.72 parts per million (ppm) for full-period exposures (51-1...

A Cohort Mortality Study of Chemical Laboratory Workers at Department of Energy Nuclear Plants

OBJECTIVE This study evaluates the mortality experience of 6,157 chemical laboratory workers employed at United States Department of Energy facilities. METHODS All cause, all cancer and cause-specific standardized mortality ratios were calculated. Cox regression analyses were conducted to further evaluate the relation between chemical exposure and mortality risk due to selected cancers. RESULTS The mortality due to all causes combined and all cancers combined were below expectation for the cohort. There were no statistically significant elevations reported among males for any specific cancer or non-cancer outcome. There no statistically significant elevations among females for any specific non-cancer and most specific cancers; however, multiple myeloma deaths were significantly elevated (SMR = 3.56; 95% CI = 1.43-7.33; number of observed deaths, n = 7). Statistically significant elevations were seen among workers employed 20+ years for leukemia using both 2- and 5-year lag periods. Also, a statistically significant positive trend of elevated lung cancer mortality with increasing employment duration was seen using both 5- and 10-year lags. A similar trend was seen for smoking related cancers among men. CONCLUSION While lymphatic and hematopoietic cancer mortality was below expectation, a significant elevation of multiple myeloma deaths among females and an elevation of leukemia among workers employed 20+ years (possibly due to radiation and benzene exposure) were observed. A NIOSH case-control study is underway to examine more closely the relation between multiple myeloma and a variety of chemical exposures among workers employed at the Oak Ridge K-25 facility.

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.

Estimating the Contribution of Individual Work Tasks to Room Concentration: Method Applied to Embalming

A new approach for estimating emission rates from continuous concentration data was developed and applied to formaldehyde measurements collected during 25 embalmings. The instantaneous emission rate was estimated from the contaminant mass balance, which set the rate of emission equal to the sum of the rate of buildup in the room and the rate of removal in the exhaust flow. The generation rate of each specific work task was modeled using an equation that considered both the buildup and decay of the generation rate. Each term of the full modeling equation corresponded to a work task or event that occurred during the embalmings. The expected formaldehyde contribution of individual work tasks or events was then estimated by integrating each term using the gamma function. The work tasks or events with the largest formaldehyde contributions were aspiration of viscera after treatment with cavity fluid, embalming fluid spill, application of osmotic gel, and trocar cavity infusion. This analysis showed the relativ...

Use of Historical Uranium Air Sampling Data to Estimate Worker Exposure Potential to Airborne Radioactive Particulate in a Uranium Processing Facility

Historical industrial hygiene monitoring records from a uranium processing plant were collected and analyzed to characterize exposure potential to airborne radioactive particulate. More than 2,100 samples were collected during the period of 1954-1968. The data was organized by job title, plant number, and year of measurement. Laboratory analysis of air samples indicated a wide range of potential exposures to the alpha-emitting particulate. Logarithmic transformation of the data was necessary to approximate Gaussian distributions. Geometric Mean (GM) values were used as the measure of central tendency within years. GM values ranged from 23-49 disintegrations per minute per cubic meter of air sampled (dpm/m3) with the years 1963 and 1964 being significantly higher than other years (ANOVA: p < 0.05). When comparing exposure potential across plants, GM ranged from 20-68 dpm/m3, with plants 5 and 8 being significantly higher than the others (ANOVA: p < 0.05). Exposure potential for specific job titles across the plants varied widely. GM for clerks was the lowest (11 dpm/m3) while furnace operators were the highest (235 dpm/m3). Other job titles with potentially high exposures were chemical operators, forklift operators, machine operators, and furnace operators. This analysis indicates the magnitude and distributions of worker exposure to alpha-emitting airborne particulate. Additional analysis and epidemiologic studies are planned for this facility.