Two veterans groups are suing the VA in the case of illnesses caused by exposure to contaminated drinking water at Camp Lejeune, North Carolina.

The organizations — The Few, The Proud, The Forgotten and Vietnam Veterans of America — filed suit Tuesday for documents related to disability claims and the Veterans Affairs Department's use of subject-matter experts to weigh in on them. The water was tainted by organic solvents and other cancer-causing chemicals from 1953 through 1987.

The groups filed a Freedom of Information Act request for the documents in December but say the VA has not responded.

"Our FOIA, which has gone unanswered, is to find out who the subject-matter experts are, what kind of credentials they have ... the VA doesn't want us to know that," said Jerry Ensminger, a founder of The Few, The Proud, The Forgotten and a retired Marine master sergeant whose 9-year-old daughter died of leukemia in 1987.

Under the Camp Lejeune subject-matter expert program, all documents related to a claim, including medical records and physician recommendations, are reviewed by a designated expert who recommends whether to accept or reject it.

Since the subject-matter program was introduced in 2012, Camp Lejeune claim approvals have dropped from 25 percent to 8 percent, according to the groups.

The Camp Lejeune subject-matter expert program is the only disability claims process within the VA that requires the third-party review.

"All of the pronouncements about this being the most open and transparent administration in history don't reflect what is happening at VA, in this instance and many others," said Rick Weidman, director of government relations for Vietnam Veterans of America. "It's time for the White House to make VA clean it up."

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Nearly a million people, including troops, family members and civilian employees, may have been exposed to volatile organic compounds and other chemicals such as benzene and vinyl chloride in the drinking water at the coastal Marine Corps base, from 1953 until at least 1987, when the water treatment facilities supplying the contaminated water were closed.

Roughly 10,000 disability claims have been filed to the VA related to Camp Lejeune water toxicity.

Democrat Richard Blumenthal, who sits on the Senate Veterans Affairs Committee and represents the state of Connecticut, where the lawsuit was filed on behalf of the groups by the Yale Law School Veterans Legal Services Clinic, said Tuesday that the VA should expedite its response to the groups' FOIA.

"The VA's lack of response to these brave men and women is utterly and completely unacceptable ... The subject-matter expert program deserves real searching, penetrating scrutiny. The lawsuit makes this point very, very well," Blumenthal said.

Patricia Kime covers military and veterans health care and medicine for Military Times. She can be reached at pkime@militarytimes.com.