animals. Measured outcomes from such studies should include gross and histologic pathology of the lungs, pulmonary lymph nodes, and kidneys for evidence of fibrosis, proliferative lesions, and tumors and include tumor-frequency data based on dose and tissue uranium concentrations. Biomarkers of cytogenetic effects (such as SCEs, micronuclei, HPRT mutations, and chromosomal abnormalities) in lymphocytes should be measured immediately after exposure and periodically thereafter. Spermatogonial cells also should be examined for chromosomal aberrations in the testes. The latter would provide information on the possible heritable nature of the aberrations.
Dust collected from inside tanks should be analyzed for other metals and chemicals that could potentially enhance the carcinogenicity of DU through such mechanisms as inhibition of DNA repair. On the basis of such analyses, it may be necessary to factor in the effects of coexposures to other carcinogens in cancer risk assessments.
The committee recommends research into whether there is a chemical mechanism of uranium carcinogenesis.