Sarin gas was responsible for the sickening of approximately 250,000 American soldiers who served during the 1990-1991 Persian Gulf War according to a recently released study.

Following the conflict, nearly one-third of all who deployed reported unexplained chronic symptoms. In the following years, veterans who sought medical help at the Department of Veterans Affairs were met with skepticism and referred for mental health treatment.

First known as Gulf War Syndrome, the malady is now termed Gulf War Illness.

In a published study in the journal Environmental Health Perspectives, it was determined that American soldiers were exposed to sarin gas. Specifically, those who were exposed and had a weaker variant of a gene that help digest pesticides were nine times more likely to have symptoms.

"Quite simply, our findings prove that Gulf War Illness was caused by sarin, which was released when we bombed Iraqi chemical weapons storage and production facilities," said Dr. Robert Haley, director of the Division of Epidemiology in the Internal Medicine Department at University of Texas Southwestern Medical Center.

"There are still more than 100,000 Gulf War veterans who are not getting help for this illness and our hope is that these findings will accelerate the search for better treatment."

The researchers' hypothesis was that if an individual has a strong form of a specific gene, and that person is exposed to low-level sarin, then that gene makes a strong isoenzyme that destroys sarin in the blood. Conversely, if one has a weak form of the gene the person will become sick.

"You've heard the expression 'correlation does not equal causation,' right? That's true, unless you are dealing with a gene-environment interaction."

American and allied soldiers were most likely exposed to sarin and cyclosarin, an organic phosphate also used as a chemical weapon, when a bunker housing chemical weapons at the Khamisiyah Ammunition Storage Depot in southern Iraq was destroyed.

A plume of contaminants spread across a 25-mile radius. Other soldiers may have been subjected to low levels of contaminants, as they reported their chemical weapons alarms went off in the absence of an attack.

In 1997, a Congressional investigation concluded that the Departments of Defense and Veterans Affairs had little interest in finding a cause and blamed the symptoms on mental health issues.

In light of the new research, Haley is hopeful the new findings make it easier for veterans to access health care and benefits and open up further research into possible treatments.