1. ^aCincinnati Children's Environmental Health Center, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
2. ^bDepartment of Environmental Health, University of Cincinnati, Cincinnati, Ohio, USA
3. ^cHendecagon Corporation, Oak Ridge, Tennessee, USA
4. ^dInstitute for the Study of Health, University of Cincinnati Medical Center, Cincinnati, Ohio, USA

Correspondence: Dr. S.M. Pinney, Department of Environmental Health, University of Cincinnati, P.O. Box 670056, Cincinnati, Ohio 45167-0056, USA. Tel.: +1 513 558-0684; Fax: +1 513 558-4240; E-mail: susan.pinney@uc.edu

Received 15 August 2007; Accepted 25 October 2007; Published online 9 January 2008.

Abstract

The Feed Materials Production Center (FMPC) at Fernald, Ohio produced uranium metal products for use in Department of Energy defense programs. Radium-contaminated waste material was stored on-site in two K-65 silos on the west side of the facility and provided a source of ²²²Ra. The initial objective of this study was to estimate radon exposures to employees at FMPC working from 1952 to 1988. A modified Gaussian plume model was used to estimate exposures to workers. In an effort to validate these model-based estimates, we used 138 CR-39 film assays from window glass sampled in buildings throughout the site. Results from the CR-39 assays indicated a second substantial source of radon, the smaller Q-11 silos located in the production area. A response-surface regression analysis using a cubic spline model was fit to the CR-39 data to estimate ²¹⁰Po surface activity levels at geographic coordinates throughout the facility. Knowledge of the age of the glass, the amount of contaminated waste in the Q-11 silos, and ²¹⁰Po decay rates were used to estimate annual exposures to radon decay products (WLM: working level months). Estimated WLM levels associated with the Q-11 source term indicated that employees working in the vicinity during the period when they were filled with radium-contaminated waste (1952–1958) received substantially higher radon exposures than those from the K-65 source during this period. Results of the two models, corresponding to the K-65 and Q-11 sources, were combined to estimate WLM levels by year for each of the 7143 Fernald workers during the period 1952–1988. Estimated cumulative exposures to individual workers ranged from <0.5 to 751 WLM. Estimated radon exposures from this newly discovered source have important implications for future epidemiologic studies of lung cancer in workers at the Fernald facility.