Exposure assessment for a cohort of workers at a former uranium processing facility

Our plain-English summary of Exposure assessment for a cohort of workers at a former uranium processing facility, by J.L. Anderson, R.D. Daniels, D.A. Fleming, et al (Journal of Exposure Science & Environmental Epidemiology, 2012).

The study

• Authors: J.L. Anderson, R.D. Daniels, D.A. Fleming, C.Y. Tseng
• Journal: Journal of Exposure Science & Environmental Epidemiology
• Published: 2012;22(4):324-30
• Cited by: 17 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Exposure was assessed for a cohort of 6409 workers at a former uranium processing facility as part of a mortality study. Workers at the facility had potential for exposure to a wide variety of radiological and chemical agents including uranium, thorium, radon, external ionizing radiation, acid mists, asbestos, and various solvents. Organ dose from internal exposure to uranium was assessed, along with dose from external ionizing radiation and exposure to radon. Qualitative assessment of exposure to thorium, acid mists, asbestos, coal dust, welding fumes, and other chemicals was also performed. Mean cumulative organ dose from internal uranium exposure ranged from 1.1 mGy (lung) to 6.7 μGy (pancreas). Mean cumulative external ionizing radiation dose was 13.4 mGy. Mean cumulative radon exposure was 26 working level months (WLMs). The chemical agents to which the largest numbers of study subjects were exposed were acid mists, machining fluids, and a tributyl phosphate/kerosene mixture used in the refining process.

In plain English

Researchers estimated exposures for 6409 workers at the Fernald Feed Materials Production Center, a former uranium processing plant near Cincinnati, Ohio. This groundwork for a mortality study did not report disease or death. Each had worked at least 30 days between 1951 and 1985. Radiation dose was estimated from uranium taken into the body, using urine tests, and from external radiation, using badges; radon exposure came from work histories and a model. Thorium and nine chemical agents, including asbestos, were assessed only qualitatively, using work histories plus plant documents and air and bioassay data for thorium, and process records and site knowledge for chemicals. Mean cumulative lung dose from uranium was 1.1 mGy (5998 workers), mean external dose 13.4 mGy (6003), and mean radon exposure 26 working level months (all 6409). Of these, 225 were classed as potentially exposed to asbestos, for an average of 9.2 years; asbestos was mainly linked to site support work. No asbestos fiber type was named. The authors noted that this yes/no assessment, used because chemical monitoring data were limited, could have misclassified workers.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Exposure assessment for a cohort mortality study (methods and descriptive exposure estimates; no health outcomes reported)
• Who was studied: 6409 workers with at least 30 days of employment by National Lead of Ohio between 1951 and 1985 at the Fernald Feed Materials Production Center, about 18 miles northwest of Cincinnati, Ohio, USA. The workers were followed through 31 December 2004.
• Exposure: Two radiation doses were estimated: organ dose from internal uranium (from urine bioassay) and external ionizing radiation dose (from dosimeter badges). Radon exposure, in working level months, was estimated by combining work histories with a previously developed radon exposure matrix. Thorium was assessed qualitatively from work histories, plant historical documents, and air and bioassay data. Nine chemical agents were assessed as yes/no from work history (job title, work organization and location), process records and site-specific knowledge. The nine agents were nitric acid/nitrogen dioxide, machining fluids, hydrofluoric acid, tributyl phosphate/kerosene, vehicle exhaust, asbestos (fiber type not stated), trichloroethylene, coal dust and welding fumes.
• Main results:
  • Among 5998 workers, mean cumulative absorbed lung dose from internal uranium was 1.1 mGy (SD 3.3 mGy). This was the highest of the six organs assessed; the pancreas had the lowest mean, 0.0067 mGy (Table 4).
  • Cumulative external radiation dose across the 6003 workers with monitoring data had a mean of 13.4 mGy and a median of 2.0 mGy.
  • All 6409 workers were assumed to be exposed to radon. Their cumulative radon exposure had a mean of 26 and a median of 3.9 working level months.
  • 150 workers were determined to be exposed to thorium at Fernald.
  • The chemical agents assigned to the most workers were nitric acid/nitrogen dioxide (45%), machining fluids (32%), hydrofluoric acid (31%) and tributyl phosphate/kerosene (29%).
  • 225 workers were classed as potentially exposed to asbestos. Their mean cumulative duration of potential exposure was 9.2 years (SD 8.6), with a median of 5.8 years.
  • Asbestos, vehicle exhaust, coal dust and welding fumes were mainly associated with site support activities, generally with less potential for internal uranium exposure.
• The authors' conclusion: The authors concluded that mean internal and external ionizing radiation doses at the facility were relatively low compared with other uranium plants operating in a similar timeframe.
• Limitations the authors state:
  • Chemical exposure, including asbestos, was assessed only qualitatively (yes/no), because only limited chemical monitoring data were available.
  • Work history data problems, such as imputation, discrepancies between databases, and errors or missing data, could have caused misclassification.
  • External doses may be biased downward because monitoring was incomplete, especially for women.
  • Assuming a single particle size and absorption type for the whole cohort introduced a large amount of shared uncertainty in the internal dose estimates.
  • Intakes were calculated from single-void urine samples, which introduced large biological variability.

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• Serum levels of pantropic p53 protein and EGF-receptor, and detection of anti-p53 antibodies in former uranium miners (SDAG Wismut) — J. Schneider, P. Presek, et al. (1999)
• Occupational cohort study of current and former workers exposed to chrysotile in mine and processing facilities in Asbest, the Russian Federation: Cohort profile of the Asbest Chrysotile Cohort study — J. Schüz, I. Bukhtiyarov, et al. (2020)
• USTUR Special Session Roundtable-US Transuranium and Uranium Registries (USTUR): A Five-decade Follow-up of Plutonium and Uranium Workers — S.Y. Tolmachev, M.J. Swint, et al. (2019)
• Analyses of radiation and mesothelioma in the US Transuranium and Uranium Registries — H. Gibb, K. Fulcher, et al. (2013)

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