WASHINGTON -- Confronted with new evidence suggesting that nearly 100,000 U.S. troops may have been exposed to a cloud of Iraqi nerve gas after the 1991 Persian Gulf war, the Pentagon announced Thursday that it would try to determine whether even more troops were exposed to poison gas when large Iraqi weapons dumps were bombed during the war itself.
The new evidence, developed from advanced computer models made public Thursday, showed that an estimated 98,900 troops were in the path of a plume of nerve gas unleashed when a battalion of U.S. combat engineers blew up the Kamisiyah ammunition depot in southern Iraq in March 1991, shortly after the war.
That is five times the Pentagon's earlier estimate of the possible exposure and represents almost one-seventh of all Americans who served in the war.
The new, larger estimate appeared to surprise officials at the Pentagon and the CIA and prompted an announcement Thursday that the same modeling techniques would be used to determine the size of the plumes created when U.S. bombers attacked much larger Iraqi weapons sites in the opening weeks of the war, including factories where chemical and biological weapons were produced. Earlier, less sophisticated models suggested that the poison gas released from those sites did not reach U.S. troops.
Defense Department officials insisted that the troops were exposed to only trace levels of sarin, a deadly nerve gas, as a result of the demolition of the Kamisiyah depot and that the available scientific evidence suggested that such low levels of the poison should not create lasting health problems for the veterans.
But some scientists and doctors are not so sure, given how little research has been done on the health effects of human exposure to low levels of nerve gas.
A University of Texas study published this year in The Journal of the American Medical Association suggested that gulf war veterans were suffering from exposure to a combination of chemicals, including minute levels of nerve gas.
The General Accounting Office, an investigative arm of Congress, said in a report last month that there was "substantial evidence" linking nerve gas and pesticides to the sorts of health problems seen among veterans of the war.
"In the absence of data, can you say one way or another?" said Thomas L. Garthwaite, deputy under secretary for health at the Department of Veterans Affairs, who appeared at a Pentagon news conference Thursday. "We're attempting to keep an open mind and let the science determine this."
Many gulf war veterans have complained of a variety of health problems, notably digestive ailments and memory loss, that they attribute to their service in the war, and more than 100,000 veterans have sought special medical checkups offered by the Pentagon and the Department of Veterans Affairs. Some researchers believe that their problems are more likely the result of wartime stress, not chemical weapons.
The computer models made public Thursday by the Defense Department and the CIA showed that the plume of sarin created by the demolition of chemical rockets in a dirt pit at the Kamisiyah depot on March 10, 1991, traveled nearly 300 miles over three days.
The models suggest that the cloud eventually wafted across large stretches of southern Iraq, Kuwait and northern Saudi Arabia, where the 98,900 U.S. troops were located, most of them from elements of the Army's 7th Corps and the 18th Airborne Corps. The Pentagon is sending all of them a letter alerting them to the possible exposure.
Defense Department officials said they also believed that some Egyptian and Syrian troops who took part in the U.S.-led military coalition against Iraq, as well as Saudi and Kuwaiti civilians, also might have been exposed to low levels of sarin as a result of the demolition, and that their governments were being notified.
For more than five years after the war, the Pentagon and the CIA insisted that they knew of no evidence to suggest that U.S. troops were exposed to Iraqi chemical or biological weapons, even though Iraq was known to have huge stocks of the weapons before the gulf war and had not hesitated to use them in its war against Iran.
But the government's account changed last year, after United Nations weapons inspectors visited Kamisiyah and found evidence that chemical weapons had been stored at the depot when it was blown up in 1991.
The Pentagon at first suggested that only a few hundred U.S. troops might have been exposed to nerve gas as a result of the demolition. The official estimate later grew to 5,000, and then 20,000, and now nearly 100,000.
Copyright 1997 The New York Times Company