Congress Poised to Help Veterans Exposed to ‘Burn Pit’ Toxins Over Decades of War

“It took decades and decades for the U.S. government to acknowledge that Agent Orange created devastating health effects for soldiers,” Ms. Klobuchar said. “We can’t let that happen again. I think you’re not going to get help in the courts, so we are going to have to step up — a lot of this will be oversight.”

Lawmakers and some doctors say that the Pentagon has also been doubtful of claims.

“It thought it was telling that last hearing, D.O.D. refused to send a representative,” said Representative Tulsi Gabbard, Democrat of Hawaii, referring to the Defense Department. She has helped sponsor legislation to evaluate the exposure of service members to toxic chemicals.

“There is no question a large number of individuals were exposed to high levels of toxic waste,” said David A. Savitz, who served as the chairman of a committee that studied the issue for the veterans department. “But when you go to the level of ‘show me’ the increased risk of the health conditions, that’s where the evidence breaks down pretty quickly.”

Some doctors — and many patients and their families — are more certain.

“I started seeing young people with similar types of presentations of uncharacteristic malignancies at young ages,” said Dr. Warren L. Alexander, an oncologist who has worked extensively with veterans at the William Beaumont Army Medical Center in El Paso. “There were about 10 percent of unexplained malignancies, where the patient had no history of drinking or smoking. When you have very aggressive cancers that do not respond to standard therapy, that’s what makes you think it was due to exposure.”

In 2004, Dr. Robert F. Miller of Vanderbilt University studied soldiers who returned from Iraq with unexplained shortness of breath. He performed surgical biopsies on about 60 veterans’ lungs, which in most cases revealed evidence of constrictive bronchiolitis, an incurable disease stemming from tiny particles lodged in the airways.

Many believe that the small number of Americans serving in the military — less than 1 percent of the population — has kept the issue from public view.

“The burn pit issue has not gained traction in terms of research money or public policy,” said Dr. Anthony M. Szema, an allergist-immunologist and the former chief of allergy medicine at the Veterans Affairs Department who has researched the relationship between particles and respiratory illnesses. “I have been invited to give lectures at the Pentagon and it’s two hours of them yelling at me. They understand there is a problem, but they don’t want to take the blame for it.”