The Veterans Affairs Department must learn to favor veterans when deciding whether to approve claims for illnesses related to environmental exposures and contaminants, senators said during a Tuesday hearing on Capitol Hill.

From the South China Sea to the Arabian Desert, from Iraq to Camp Lejeune, North Carolina, and elsewhere, service members have been exposed to pollutants that have harmed their health, yet the VA continues to engage in "passive-aggressive rebuttal of scientific findings" to deny them health care and compensation, charged Sen. Richard Burr, R-N.C.

Speaking to the Senate Veterans' Affairs Committee, Burr implored its members to increase their oversight of the VA's handling of toxic exposure claims, adding that while he is encouraged by VA Secretary Bob McDonald's recent efforts to improve the department's understanding of exposure-related illnesses, more needs to be done.

"To this day I remain appalled at the way the United States government has treated these families," Burr said, speaking of the more than 1 million residents of Camp Lejeune who consumed contaminated drinking water at the installation from the mid-1950s through 1987. "Our government rewarded them for their service by negligently poisoning them."

Sen. Kirsten Gillibrand, D-N.Y., and Sen. Steve Daines, R-Mont., have sponsored a bill, the Blue Water Navy Vietnam Veterans Act, which would grant benefits to hundreds of thousands of sailors who served on aircraft carriers, destroyers and other large Navy ships in the waters off Vietnam and have illnesses associated with exposure to the toxic defoliant Agent Orange.

The VA provides compensation and care for veterans who served in the "brown water" Navy — small boats and crafts that patrolled rivers and inland waterways — but does not acknowledge exposure among many veterans who served on the larger vessels at sea.

The VA argues that those sailors were not directly exposed and therefore, their illnesses are not service-connected.

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

But Gillibrand cited an Australian Veterans Affairs Department study that found its vets were exposed to Agent Orange when its ships distilled seawater contaminated with the herbicide for onboard use.

She said blue water veterans are suffering needlessly as a result of "arbitrary bureaucracy."

"Instead of treating every Vietnam veteran who suffers from disease caused by Agent Orange, the VA is only treating those who stepped on Vietnam's soil or served on boats on inland waters," Gillibrand said. "This is arbitrary and capricious."

Sen. Richard Blumenthal, D-Conn., and Sen. Jerry Moran, R-Kan., have co-sponsored a bill that would require VA to establish a center for researching the health conditions of descendants of troops who may have been exposed to toxic chemicals.

Blumenthal urged the VA to speed up the process for recognizing the health consequences of exposure to toxic chemicals.

"Here's what we know about the modern battlefield: There are all sorts of toxic substances, many more than the lay person can imagine. [It's] dangerous even for those who didn't serve in combat," Blumenthal said.

Several birth defects in children of Vietnam veterans are considered by the VA to be service-connected, including spina bifida for children of male vets and 18 health conditions for children of mothers who served in that combat zone.

But the Blumenthal-Moran bill would require VA to look at the health of military offspring beyond the Vietnam era, to include the Persian Gulf War and the conflicts in Iraq and Afghanistan.

David McLenachen, VA acting deputy secretary for disability assistance, said the Veterans Benefits Administration is taking steps to improve its determinations for claims related to environmental exposures, to include contracting with the Institute of Medicine and other scientific bodies to study the issues.

He said the VA uses the research to change its policies as needed and cited recent examples including the recognition of Air Force reservists who flew in C-123 aircraft that had been used to spray Agent Orange during the Vietnam War; veterans exposed to mustard gas who have been granted presumptive service-connection for respiratory illnesses; and a recent announcement that rules will be amended to establish presumptive service connection for conditions related to the contaminated drinking water at Camp Lejeune.

But those changes likely would not have come about if not for small groups or individual veterans who fought for recognition — a process that often takes years.

Gillibrand pointed out that the Australian study was undertaken after Australian officials noticed higher rates of cancers and illnesses among its blue water Vietnam veterans, then noted that the VA rarely initiates efforts to resolve such mysteries.

Retired Marine Master Sgt. Jerry Ensminger testified Tuesday for the seventh time about the Camp Lejeune water problem, an environmental disaster that claimed the life of his 9-year old daughter Janey in 1985.

"Agents with VA have expended more effort, time and money devising methods to deny Camp Lejeune victims their rightful benefits rather than providing them," Ensminger said.

McLenachen acknowledged that the process is slow.

"As the science develops so must our policy," he said. "We need to learn how to streamline this process."