Veterans who served on Navy ships off Vietnam and have diseases linked to Agent Orange were buoyed Thursday by House passage of a measure that could expand their Veterans Affairs benefits.

An amendment added to the House Military Construction and Veterans Affairs funding bill would require the department to presume these veterans were exposed to the toxic herbicide and provide health care and compensation if they are sick as a result.

The initiative still must pass the Senate before it becomes law, but it marks a major step forward for a cause that has languished in Congress and at the VA for years.

"Members from both sides of the aisle have been fighting to make sure these sailors get the health care they need," said amendment sponsor Rep. Chris Gibson, R-N.Y. "We will never turn our backs on our service men and women."

VA already has presumed that sailors and Marines who served on ships on inland waterways in Vietnam faced the same risks as those who served on the ground and provide them benefits if they have one of several diseases linked to herbicide exposure, including Parkinson's disease, diabetes and peripheral neuropathy.

But VA does not consider "blue water veterans" to have been directly exposed to the herbicide and therefore are ineligible for benefits.

Advocacy groups and legislators say a VA policy that excludes bays and harbors from the definition of "inland" is unfair, and, they add, studies indicate that service members may have been exposed when the ships they were assigned to used distilled contaminated sea water for bathing and drinking.

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"These personnel were heavily exposed to this toxin through shipboard water systems that drew Agent Orange-affected waters through filtration systems," said retired Navy Cmdr. John Wells, Military-Veterans Advocacy executive director. "Although they may never have been on land where the toxin was sprayed, they were still exposed through eating, drinking and bathing."

The Institute of Medicine released a study in 2011 saying there is not enough information to determine whether these veterans were exposed to Agent Orange.

Despite the research gap, Wells said many of the estimated surviving 90,000 sailors and Marines who served are sick and dying from Agent Orange-related diseases.

"There is incontrovertible, scientific proof of this exposure, but the Department of Veterans Affairs has been reticent about restoring benefits, even in light of recent court cases," Wells wrote in a recent press release.

Sen. Kirsten Gillibrand, D-N.Y., has introduced similar legislation in the Senate.

A spokesman for Gibson said Thursday the congressman was working closely with colleagues to ensure that similar language is passed in the Senate.

The House Military Construction and Veterans Affairs appropriations bill passed 295-129.

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