Its study, of the path of a chemical gas cloud which contained the nerve agent Sarin, released when weapons were destroyed, reveals the extent to which British and American forces came into contact with it.
The Ministry of Defence has never acknowledged that illnesses endured by Gulf War veterans were caused by chemical weapons, but this new evidence will raise further suspicions among veterans that they have suffered because of it.
The long-term effects from low-level exposure to Sarin are unknown, but short-term exposure can cause watery eyes, tightness of chest, muscle twitching, sweating and headache. Higher dosages produce incapacitation and result in death.
An MoD spokesman said: "The revised plume covered areas in which some British units would have been located. The MoD has been seeking to identify these in the light of detailed modelling information received from the US Department of Defense and contemporary records of British troop locations."
The American authorities are seeking to make medical assessments of an additional 80,000 US troops. The research suggests that thousands of British troops based north-west of Kuwait City, such as those with the 4th Armoured Brigade, which included the Royal Scots and the Royal Regiment of Fusiliers, and regiments of the Royal Artillery, may have been exposed. The MoD spokes- man said John Reid, the Armed Forces Minister, briefed Gulf veterans' representatives last week, but no decisions have been made on what action to take.
The CIA study concludes: "The number of troops who have been exposed to very low levels remain a concern. We need to understand, through our epidemiological and medical work, the effects of low-level chemical exposure for our veterans now and for the future."
It had previously been believed that the 400 or so members of 32 Field Hospital, based in Saudi Arabia, were the only British troops in the path of the gas cloud. Several among those working with 32 Field Hospital are now suffering from debilitating conditions, including chronic fatigue, irritable bowel syndrome, memory loss, asthma, emphysema, painful joints and non-specific rashes.
The CIA researchers attempted to replicate the Khamisiyah explosion at the military testing ground at Dugway, Utah. The Khamisiyah pit was detonated by the Americans on 10 March 1991. During the next three days the wind changed repeatedly, wafting the gases from up to 500 chemical rockets across the desert. After the tests, the Americans revised their assessment of the risk area from a 25km radius of Khamisiyah to a distance of up to 450km. The US Department of Defense still maintains that the risk is low. Questioning of 7,400 US troops, among those based closest to Khamisiyah, revealed 99 per cent had no physical effects related to Sarin exposure.
Terry Walker had been in a forward position with the Royal Army Ordnance Corps: "The alarms had been put away and the NBC [nuclear, biological and chemical warfare] suits were not being used," he said.
Mr Walker, 38, can no longer work. He has rheumatoid arthritis and experiences flashbacks. Although he has been offered a full war pension, it has not been linked to service in the Gulf.