If Lt. Col. Jim Gentry and his doctors were right about the cause of his cancer, the Indiana National Guard officer didn't die for his country -- he died for defense contractor KBR.

Gentry's death from lung cancer last week is being recorded as the US's first fatality from exposure to a cancer-causing toxin in Iraq, according to the Evansville, Indiana, Courier & Press.

In 2003, Gentry commanded a 600-strong force providing security for KBR's refittal of the Qarmat Ali water-pumping plant, which provided water needed for oil extraction. Gentry and others claim that during that time they were exposed to hexavalent chromium, a cancer-causing toxin that the Iraqis who had built the plant had used as anti-corrosive material.

In a lawsuit filed last year, Gentry and 15 other plaintiffs said KBR, at the time a subsidiary of Halliburton, was aware that soldiers and civilian contractors were being exposed to hexavalent chromium months before they told the people working at the site.

Researchers have linked hexavalent chromium to lung cancer and leukemia, as well as a variety of liver and kidney problems. It's the same compound that poisoned residents of Hinkley, California, in a case that was made famous by the movie Erin Brockovich.

Gentry was diagnosed in 2006 with a rare form of lung cancer that doctors attributed to exposure to hexavalent chromium. When he died last week, he was the first soldier officially recorded to have died from exposure to toxins in Iraq.

But as the Courier & Press notes, Gentry may not have been the first to die from exposure at Qarmat Ali. Sgt. David Moore died of lung disease in February of this year, and his death was ruled service-related. Moore was a smoker, making his diagnosis more difficult to pinpoint.

In an investigative report last year, CBS News obtained documents purportedly showing that KBR employees had "concerns about the toxins in one part of the plant as early as May of 2003," one month after Gentry's unit arrived at the facility, but three months before the company informed the soldiers.

CNN reported at the time the lawsuit was launched:

The Guardsmen and civilian contractors who worked there have described walking on and sitting near the bright orange powder that was widely dispersed throughout the grounds of the water plant. The chemical was believed to have been left behind by forces loyal to Saddam Hussein.

Some of the Guardsmen already suffer from nasal tumors or respiratory system problems and other health problems, according to the lawsuit. One of the guardsmen may have died from the exposure, though the exact cause of his death earlier this year is still not clear.

"KBR managers knew full well long ago that this stuff was incredibly dangerous. But there was no information about it for years. And now these soldiers are facing some pretty serious health concerns. They're going to be stuck with this the rest of their lives," said Mike Doyle, one of the Houston attorneys representing the Guardsmen. "The most frustrating thing is that these guys are finding out years later that they were exposed to something."

"I understand and accept there's danger with my line of service, in my line of service," Gentry said in the lawsuit deposition, as quoted at the Courier & Press. "What's very difficult for me to accept is if I'm working for KBR and they have knowledge of hazardous chemicals on the ground that can cause cancer and (they don't) share that knowledge, then that is putting my men at risk that is unnecessary."

Indiana Sen. Evan Bayh has involved himself in the controversy, introducing a bill in Congress in October that would guarantee lifetime health care for soldiers exposed to hazardous materials in war zones.

"You served our country honorably," Bayh told the soldiers who served at Qarmat Ali, as quoted last week at the Courier & Press. "You deserve the best medical care possible. We shouldn't put the burden of proof on you, because there are photographs of piles of this stuff sitting around there."