committee encourages studies that will provide continued long-term follow-up of uranium processing workers, particularly those that incorporate new methods of measuring dose and utilize sophisticated statistical analyses.
The committee recommends additional studies in experimental animals to investigate specific effects of depleted uranium.
Animal studies provide the opportunity to carefully study the effects of depleted uranium in isolation from other exposures. Controlled experimental conditions provide a contrast with studies of veterans or workers in industrial settings as both populations have concomitant exposures to many other potential hazards. Of particular importance are studies of cognitive function, neurophysiological responses, brain DU concentrations, and the transport kinetics of DU.
The committee recommends the following avenues of research to augment our understanding of long-term effects of exposure to sarin.
The committee recommends careful long-term follow-up of populations exposed to sarin in the Matsumoto and Tokyo terrorist attacks.
The Matsumoto experience shows that direct exposure to sarin, particularly in intermediate to high doses, is associated with the acute cholinergic syndrome. Further, follow-up studies of Matsumoto demonstrate that significant chronic symptoms from sarin exposure persist and include visual disturbances, fatigue or asthenia, and headache. These chronic symptoms appear to be dose dependent. Follow-up studies, with well-defined control populations, will provide information related to possible long-term health effects.
The Tokyo sarin experience also confirms that intermediate doses of sarin leads to the acute cholinergic syndrome. Visual disturbances are frequent sequelae of acute exposure. Neurophysiological testing of a small group of asymptomatic people exposed to sarin shows chronic changes in visual and event-related evoked potentials and vestibulocerebellar function months after the acute syndrome had subsided. While these neurophysiological data are suggestive of subtle, persistent central nervous system (CNS) effects from sarin, long-term follow-up studies are required.
Of particular importance is a study that would include a group of individuals that presented symptoms of acute sarin poisoning at the time of exposure, as well as a group that was involved in the incidents but did not experience acute illness. These two groups, together with an unexposed matched control group, would provide important information on whether the long-term sequelae already reported occur in those who have been exposed to subsymptomatic levels of sarin. Studies should include neuropsychological testing, electroencephalogram (EEG), evoked potentials, and vestibular testing.