Alfred Procopio Jr. left the Navy in 1967, decorated with medals for his service on the USS Intrepid, an aircraft carrier deployed off the coast of Vietnam. He also came home with health problems the U.S. government has linked to exposure to the toxic herbicide Agent Orange.

Procopio is one of an estimated 52,000 veterans nationwide who were stationed on ships during the Vietnam War but are not eligible for the same disability benefits as those who put boots on the ground or patrolled the country’s inland rivers.

His case, argued in December at a federal appeals court in Washington, could extend coverage for ailments associated with the infamous herbicide to a group of sailors known as the “blue water” Navy veterans.

Parallel efforts in Congress to broaden benefits have stalled in recent years.

This spring, the House unanimously approved a measure, but the Senate balked in December because of concerns about cost and demands for more scientific study.

“We do not have another year to wait. Some of our veterans will not last that long,” Sen. Kirsten Gillibrand (D-N.Y.) said on the Senate floor. “It doesn’t make any sense.”

The legislative and legal questions are intertwined: Did Congress intend to give these sailors the benefit of the doubt when it comes to showing their medical conditions are connected to toxic exposure?

At stake for Procopio, 73, and a leader of the veterans’ group, Mike Yates, is as much as $3,000 a month.

During the war, U.S. naval forces patrolled Vietnam’s 1,200-mile-long coastline, supplied Marines on land and provided long-range artillery support. Those stationed offshore like Procopio and Yates were referred to as the “blue water” Navy in contrast to the “brown water” sailors who operated on inland waterways.

Between 1962 and 1971, the U.S. military sprayed more than 74 million liters of herbicides, including Agent Orange, to destroy crops and reduce cover for enemy forces.

Two decades later, amid scientific uncertainty, Congress passed a law to ensure veterans who “served in the Republic of Vietnam” could obtain disability compensation for certain health problems connected to exposure.

Two critical developments led to the current debate. First, Congress broadened the pool of eligible veterans. Then the Department of Veterans Affairs narrowed its interpretation of who qualifies as having “served in the Republic of Vietnam” — a definition it said excludes the offshore sailors.

Advocates for the blue water sailors point to studies that show exposure occurred through contaminated water funneled into ship distillation systems and used for drinking, laundry and cleaning. Much of the spraying was on low-lying swamps of the Mekong River Delta that flows into the South China Sea, where they were stationed.

Former veterans affairs secretary David Shulkin, who was fired by President Trump, backed the Senate bill. In the absence of reliable data or scientific certainty, “the answer must not be to simply deny benefits,” he wrote in a September letter to the Senate.

“When there is a deadlock, my personal belief is that the tie should be broken in favor of the brave men and women that put their lives on the line for all of us.”

But Secretary Robert Wilkie and four former secretaries were opposed, citing cost and need for further study. The Congressional Budget Office estimated a cost of $1.1 billion over 10 years to extend the benefits to the blue water veterans; the department put the price tag at more than $5 billion.

“We know it is incredibly difficult to hear from blue water veterans who are ailing and ill, and we have great empathy and compassion for these veterans,” Wilkie told the Senate. But Wilkie warned about the implications for an agency already struggling with a backlog of claims.

A three-judge panel of the U.S. Court of Appeals for the Federal Circuit previously heard Procopio’s case, but did not issue a decision. Instead, the court took the unusual step of rehearing the case as a full panel in December. There are more than two dozen pending cases from veterans in states throughout the country that could be affected by the outcome.

Procopio’s disability claims related to diabetes and prostate cancer were denied in 2009, after an administrative board found he was not “present on the landmass or the inland waters of Vietnam” and had not shown direct exposure to Agent Orange.

One disputed line in the statute being reviewed by the court says the presumption, entitling veterans to disability benefits, applies to any “veteran who, during active military, naval, or air service, served in the Republic of Vietnam.”

The question for the court is whether the phrase “served in the Republic of Vietnam” includes service offshore and to what extent the court should consider giving the benefit to veterans when it tries to resolve ambiguous language in law.

Procopio’s lawyers say the inclusion of the words “during active military, naval or air service” was intentional.

“Congress made clear that any veteran who developed a disease linked to Agent Orange exposure and had ‘served in the Republic of Vietnam’ within a specified time frame would be entitled to a presumption of exposure and service connection,” attorney Melanie L. Bostwick told the court.

Government lawyers say the statute is unclear and the “passage of time has not further illuminated Congress’s intent.”

“Congress did not define ‘served in the Republic of Vietnam,’ much less define it to include service in offshore waters,” according to the government’s filing.

But, the government says, Congress did give VA, not the courts, the power to determine the breadth of benefits for veterans.

Yates, the head of the Blue Water Navy Association, spent two years hunting submarines and protecting aircraft carriers on the USS Bainbridge. He retired in 2012 after a career as an engineer but has gone back to work in Las Vegas at 68 because of the high cost of treatments for prostate cancer and hypertension, both of which are considered herbicide-linked conditions.

“Their job is to take care of the veterans,” said attorney John B. Wells, a retired Navy commander who has represented Procopio in his challenge to VA.

“We did our job, they should do theirs,” Yates said.

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