No abstract

Studies of leukemia and lung cancer mortality at the Portsmouth Naval Shipyard (PNS) have yielded conflicting results. In an expanded cohort of PNS workers employed between 1952 and 1992 and followed through 1996, the all-cause standardized mortality ratio (SMR) was 0.95 (95% confidence interval, 0.93-0.96). Employment duration SMRs were elevated with confidence intervals excluding 1.00 for lung cancer, esophageal cancer, and all cancers combined. Leukemia mortality was as expected overall, but standardized rate ratio analyses showed a significant positive linear trend with increasing external radiation dose. The role of solvent exposures could not be evaluated. Findings differed by radiation monitoring subcohort, with excess asbestosis deaths limited to radiation workers and several smoking-related causes of death higher among nonmonitored workers. At PNS, asbestos exposure and possibly smoking could be nonrandomly distributed with respect to radiation exposure, suggesting potential for confounding in internal analyses of an occupational cohort.

To study the light yield nonproportionality and intrinsic energy resolution of inorganic scintillators, a Compton coincidence technique was previously designed, implemented and benchmarked. This technique provides the ability to accurately measure the electron response of scintillation materials and thus provides an accurate means of studying these characteristics. In this study, the electron responses of two "classic" scintillators (CaF,(Eu) and Bi,Ge,012 (BGO)) and a newer scintillator (Lu,Si0,:Ce3+ (LSO)) have been measured over the energy range from 5 keV to approximately 450 keV using this technique. Electron responses for all three scintillation materials are observed to increase monotonically with electron energy. BGO is observed to have the least nonproportionality, with its electron response varying about 20% over this energy range. Conversely the LSO electron response is observed to vary about 50% over this energy range and thus exhibits the largest nonproportionality.