The fierce controversy over the origins of the chronic symptoms reported by US Gulf War veterans is set to continue. Last week, an expert committee at the Institute of Medicine (IOM) concluded it could not resolve the issue because there is not enough published evidence about the effects of exposure to suspect substances.
The committee based its opinion on a close reading of 1,000 papers from the scientific literature. These were almost all reports of occupational, clinical and terrorist exposure, rather than of Persian Gulf veteran exposure.
It concluded that the papers do not provide sufficient data to place blame with any certainty on the substances of most concern to veterans — the nerve gas sarin; pyridostigmine bromide (PB), a medicine troops took prophylactically to blunt the effects of nerve gas; depleted uranium from tanks and munitions destroyed in the war; and vaccines given to some troops to prevent anthrax and botulism.
“The bottom line is that we simply don't know enough to say whether there is a connection between exposure to these agents, or combinations of these agents, and specific health outcomes that remain long after the exposure,” Harold Sox, who chaired the committee, told a news conference in Washington. Sox is professor of medicine at the Dartmouth-Hitchcock Medical Center in Lebanon, New Hampshire.
The committee said that a lack of information about actual troop exposures meant it had to review papers that did not involve Persian Gulf veterans. Even in this literature, insufficient information about the chronic effects of exposure made it impossible to draw conclusions in most instances.
There were some exceptions. The committee has now ruled out any role for depleted uranium in causing kidney disease or, in low doses, lung cancer. Conversely, three papers showed that neurological and psychological symptoms could persist for at least six months after exposure to sarin.
The committee also challenged several studies of Gulf War veterans by Robert Haley, director of epidemiology at the University of Texas Southwestern Medical Center in Dallas (see Nature 385, 187; 1997). These suggested that chronic neurological damage might be related to PB. But the IOM study noted methodological flaws in the studies, including heavy reliance on self-reporting, a small survey sample, and lack of a control group.
The IOM's report drew immediate criticism from activist veterans. They suggested that proof of links between their wartime exposure and current symptoms might lie in classified US Department of Defense information to which the committee did not have access. They also criticized the fact that the report did not consider exposure to combinations of agents, which they argued was a more likely battlefield scenario.