accidents (including fires). DU-containing projectiles struck 21 Army combat vehicles (OSAGWI, 1998). After the war, assessment teams and cleanup and recovery personnel may have had contact with DU-contaminated vehicles or DU munitions. In June 1991, a large fire, which occurred in Camp Doha near Kuwait City, led to a series of blasts and fires that destroyed combat-ready vehicles and DU munitions. Nearby troops and cleanup crews may have been exposed to DU-containing dust or residue. Other troops may have been exposed through contact with damaged vehicles or inhalation of DU-containing dust (Fahey, 2000).
The primary routes of exposure to uranium for humans are through ingestion or inhalation; the effects of dermal exposure and embedded fragments have also been studied. The amount of uranium retained in the body depends on the solubility of the uranium compounds to which the individual is exposed. Inhaled insoluble uranium concentrations may remain within the pulmonary tissues, especially the lymph nodes, for several years. Ingested uranium is poorly absorbed from the intestinal tract.
Although depleted uranium is the form of uranium that was present in the Gulf War, there are only a few studies of its health effects. Therefore, the committee studied the health effects of natural and processed uranium in workers at plants that processed uranium ore for use in weapons and nuclear reactors. The literature on uranium miners and on populations exposed to external radiation is largely not relevant to the study of uranium because the primary exposures of these populations were to other sources of radiation (e.g., radon progeny or gamma radiation). While studies of uranium processing workers are useful, these studies have several shortcomings. Although several studies involved tens of thousands of workers, even these studies were not large enough to identify small increases in the risk of uncommon cancers. Few studies had access to consistent, accurate information about individual exposure levels. Further, 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.
Lung cancer mortality has been the focus of attention in many cohort studies of workers employed in the uranium processing industry. Many of these studies were large and had a long period of follow-up. Lung cancer mortality