The approval rate for disability claims filed with the Veterans Affairs Department for illnesses related to poisonous drinking water at Camp Lejeune, North Carolina, has dropped by two-thirds since VA implemented a third-party review process to provide medical opinions on related diagnoses.

The Camp Lejeune subject matter expert program requires a VA-appointed physician to review the medical files of former troops who lived on base from 1953 to 1987 and are seeking compensation for illnesses possibly related to drinking contaminated water there.

But since the program was introduced in 2012, claims approvals have dropped from 25 percent to 8 percent, prompting critics to question the independence and training of the VA's 22 to 30-some experts, whom the department has not identified.

Veterans advocacy groups, including Vietnam Veterans of America, the Connecticut State Council of the Vietnam Veterans of America and The Few, the Proud, the Forgotten, have filed a Freedom of Information Act request for records about the subject matter expert program, seeking information on the identities, training and education of those experts.

Former Marine and Yale Law School student Rory Minnis, who is helping with the FOIA process, said VA has "largely ignored demands for basic information on the policies, procedures and qualifications of these experts."

"The subject matter expert program has been billed as a means to provide consistency of Camp Lejeune claims and to help develop VA's institutional knowledge. What the VA did not tell the veterans is what they meant by consistency is consistent denials," Minnis said during an announcement about the FOIA at Yale on Monday.

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

The Honoring America's Veterans and Caring for Camp Lejeune Families Act of 2012 required VA to treat veterans who were stationed at Camp Lejeune and have one of 15 related illnesses at no cost. The bill required VA to reimburse affected family members for health services for the named illnesses as well.

Disability claims for exposure-related illnesses, however, are decided on a case-by-case basis.

A process is underway at VA to designate three illnesses as presumed to be connected to serving at Camp Lejeune during the designated timeframe, including kidney cancer, angiosarcoma of the liver and acute myelogenous leukemia.

But for now, all Camp Lejeune disability claims are reviewed by subject matter experts who provide an opinion on whether they believe the claimant's illness is related.

The veteran never meets with the subject matter expert nor does he or she receive a copy of the expert opinion.

VA officials say that the medical opinions crafted by subject matter experts are just "one piece among many of evidence" that are considered when deciding a claim.

"That is the job of the adjudicator, to review all the evidence, determine the credibility of the evidence and the weight of the evidence," said Bradley Flohr, senior adviser for compensation services at the Veterans Benefits Administration during a community meeting on Camp Lejeune held in Tampa on Friday.

But Jerry Ensminger, founder of the Camp Lejeune family advocacy group The Few, the Proud, the Forgotten, said VA adjudicators placed too much weight on the subject matter experts' opinions, and VA has never provided an example of a claims adjudicator overriding an expert opinion.

"These people are refuting what the veterans' own doctors are saying," Ensminger said. "They are making life and death decisions that affect peoples' lives. Veterans have a right to know who these people are and what their qualifications are."

He and others also say that clinicians in the program have based their opinions on outdated or incorrect science, including one who argued that the cleaning solvent trichloroethylene does not cause cancer.

"I saw two denials for kidney cancer written by the same so-called subject matter expert that stated he'd done a comprehensive review of two decades of scientific studies and could find no evidence that TCE causes cancer," Ensminger said.

Studies dating to at least 2010 indicate that TCE is linked strongly to kidney cancer.

More than 10,000 disability claims have been filed at VA related to Camp Lejeune water toxicity, according to Minnis.

In October, the Marine Corps sent mailings to thousands of troops and veterans informing them of their eligibility to enroll in the Camp Lejeune Historic Drinking Water notification database. To date, more than 230,000 troops and veterans have enrolled.

This year, Sens. Jerry Moran, R-Kan., and Richard Blumenthal, D-Conn., along with Reps. Dan Benishek, R-Mich., and Mike Honda, D-Calif., introduced the Toxic Exposure Research bill, S 901, to support research into the health issues of veterans' children and grandchildren.

Blumenthal said Monday that veterans have a right to know the reasons claims were denied, who contributed to the decision and what documents were used to decide.

"The modern battlefield is full of toxic substances," Blumenthal said. "Whether it is burn pits and nerve gas in Iraq or Afghanistan, depleted uranium, Agent Orange in Vietnam, there is a need for a complete overhaul and reform of the method for assessing these claims and determining their validity."