Two measures introduced in Congress by lawmakers this week would overhaul the way the Department of Veterans Affairs cares for millions of former service members who were exposed to toxic substances, from atomic radiation sites in the Pacific to open-air burn pits in Iraq and Afghanistan.

The sweeping legislation, mostly focused on the issue of burn pits from recent wars, would compel VA to presume certain illnesses are linked to exposure to hazardous waste incineration, removing the burden of proof from veterans.

Lawmakers and advocates, including comedian Jon Stewart, have said inaction at VA, government skepticism of linking toxic exposure to certain illness and concerns about budgets have left legions of veterans without care.

“These individuals who volunteered to fight in these wars are now fighting their own government,” Stewart said Wednesday, ahead of the unveiling of legislation in the House. VA, he said, has built a system “that delays people and denies people.”

VA officials have said that scientific evidence linking exposure to illnesses was inconclusive. That has forced many veterans to simply give up, submit futile disability claims or seek care elsewhere.

The legislation, and the advocacy that powered it, reframe veteran care as a central cost of war, rather than an afterthought, Stewart said.

The bill introduced by Rep. Mark Takano (D-Calif.), chairman of the House Veterans’ Affairs Committee, would provide health care and benefits to as many as 3.5 million veterans believed to have been exposed to toxic material. Under the measure, VA would presume that war veterans were exposed to burn pits if they develop any of 23 cancers or respiratory illnesses after deployments in Iraq, Afghanistan and other countries that house U.S. troops.

Veterans groups and lawmakers have said vast fields dedicated to burning war detritus — plastics, batteries, destroyed vehicles and sometimes amputated limbs — wrecked the bodies of service members. In Iraq, one large pit in Balad burned continuously for years, at one point incinerating 147 tons of waste per day, Military Times reported — about the equivalent of a fully grown blue whale.

But a majority of claims related to burn pits are denied, Takano said at a news conference Wednesday, adding that his bill would address processes VA uses to identify and confirm service-related health problems.

“It’s clear VA’s process hasn’t been working,” Takano said.

VA found nearly 16,000 claims made by veterans of recent wars that included key words such as “burn pit.” About 60 percent were denied, the agency said, for reasons such as lack of medical diagnosis and an absence of evidence linking the health conditions to service.

Advocates and lawmakers celebrated the unveiling of the bills. But the measures are likely to face some opposition in Congress for what would be billions of dollars in costs.

Rep. Mike Bost (R-Ill.), a member of the House Veterans’ Affairs Committee who included a bill in the legislation, told Military.com that trimming costs could be crucial to the measure’s passage.

Takano and Sen. Jon Tester (D-Mont.), the Senate Veterans’ Affairs Committee chairman who introduced a similar bill Tuesday, did not provide estimated costs.

The human costs of inaction, advocates have said, is more stark.

Wesley Black, a former infantryman in the Vermont Army National Guard, served on two combat deployments, including at a primitive outpost in eastern Afghanistan from 2009 to 2010. Soldiers would stand guard for hours shrouded in noxious smoke drifting from a burn pit nearby, he said. Electronics, food packaging, various metals and bloody uniforms were all soaked in jet fuel and set ablaze round-the-clock.

Black was still on his tour when he developed chronic diarrhea and lost dozens of pounds. He later found blood in his stool, and VA diagnosed him with irritable bowel syndrome.

His condition worsened, and in 2017, VA diagnosed him with terminal colon cancer, he said.

Black’s cancer was “likely” caused by his exposure to burn pits in Iraq and Afghanistan, Thomas Abrams, an oncologist who treated Black at the Dana-Farber Cancer Institute, wrote in a letter in 2018.

Black’s cancer may have been caught sooner if “further investigation” had been done, Abrams wrote. Black has sued the U.S. government for medical malpractice of staff at a VA medical center in Vermont, his attorney Dan Perrone said.

Black, a 35-year-old father who has become an advocate for increased veterans care, said he is taking experimental chemotherapy targeting his liver, where the cancer has spread.

Official acknowledgment that hazardous material is the culprit behind many illnesses would be a hard-won victory for veterans who say VA has viewed their pleas for help with skepticism, Black said.

“The only thing we asked for when we came home is to take care of us. As long as I’m alive and these burn pits are a problem, I’m going to continue to fight,” he said.

In a statement, VA said it was working to accelerate changes advocates have long demanded.

“We understand that Congress and veteran service organizations and advocates are working hard on this effort of toxic exposure and burn pits — and they should,” said Terrence Hayes, VA’s press secretary.

VA, Hayes said, “is seeking every avenue possible to develop a process with the utmost rigor where presumptives can be determined in a more expedient and holistic manner.”

For decades, Vietnam veterans were denied care for exposure to defoliants such as Agent Orange. VA now presumes certain conditions are related to exposure. The proposed bills would expand care and benefits to Vietnam-era veterans who were exposed to Agent Orange in Laos, Cambodia, Thailand and elsewhere.

Those additions are important, Takano said, because the Pentagon still denies that U.S. troops operated outside Vietnam’s borders, making claims of exposure in some countries impossible to verify from government records.

The measures would also cover veterans who were exposed to radiation during cleanup efforts at atomic testing sites in the Pacific and veterans sickened after an Air Force bomber crashed in Spain in 1966. The incident triggered the release of plutonium from hydrogen bomb detonators.

Any pushback from lawmakers over cost would be disingenuous, said Jeremy Butler, the chief executive of Iraq and Afghanistan Veterans of America.

A common analogy used by advocates, he said, is the spending bills arriving now are tabs for a dinner Congress already has eaten.

“It’s not as if this is a wish list,” Butler said. “It’s providing health care for those exposed to toxins by our own hand.”