In general, animal studies have provided invaluable information on the pharmacokinetics of uranium, as well as qualitative insight into the toxicology of uranium. As discussed in this chapter, the majority of the evidence on the human health effects of exposure to uranium is from studies of workers in uranium processing mills and other facilities. Few studies of Gulf War veterans have specifically focused on the effects of uranium. Additionally, the literature on uranium miners is largely not relevant to the study of uranium per se because the primary exposure of this population was to radon progeny, which are known lung carcinogens. Although the studies of uranium processing workers are useful for drawing conclusions, the study settings have inherent weaknesses. First, even studies that involved tens of thousands of workers are not large enough to identify small increases in the relative risk of uncommon cancers. Second, few studies had accurate information about individual exposure levels. Some authors estimated the cumulative dose by following an employee’s path through various jobs whose average radiation exposure was known. Third, in these industrial settings, the populations could have been exposed to other radioisotopes (e.g., radium ore, thorium) and to a number of industrial chemicals that may confound health outcomes. Finally, no studies had reliable information about cigarette smoking, which may also confound outcomes of lung cancer. However, these cohorts of uranium processing workers are an important resource, and the committee encourages further studies that will provide progressively longer follow-up, improvements in exposure estimation, and more sophisticated statistical analyses. The committee makes recommendations in Chapter 8 related to research on depleted uranium.
The following is a summary of the chapter’s conclusions:
The committee concludes that there is limited/suggestive evidence of no association between exposure to uranium and the following health outcomes:
lung cancer at cumulative internal dose levels lower than 200 mSv or 25 cGy, or
clinically significant renal dysfunction.
The committee concludes that there is inadequate/insufficient evidence to determine whether an association does or does not exist between exposure to uranium and the following health outcomes:
lung cancer at higher levels of cumulative exposure (> 200 mSv or 25 cGy),