President Biden gives the pen he used to sign the “PACT Act of 2022” to Brielle Robinson, daughter of Sgt. 1st Class Heath Robinson, who died of cancer two years ago, during a ceremony in the East Room of the White House on Wednesday in Washington. Evan Vucci/Associated Press

WASHINGTON — President Biden on Wednesday signed into law bipartisan legislation to help veterans exposed to toxic burn pits in Iraq and Afghanistan, calling it a long overdue step toward fulfilling the country’s “truly sacred obligation” of caring for its veterans.

“This is the most significant law our nation has ever passed to help millions of veterans who are exposed to toxic substances during their military services,” Biden said. “I was going to get this done, come hell or high water.”

The bill, known as the “PACT Act,” dramatically expands the benefits and services for veterans exposed to such toxins, mainly in the two wars, who may develop injuries and illnesses that take years to manifest themselves. Those realities often made it difficult for veterans to establish a direct connection between their service and disabilities, preventing them from getting the care they needed, the White House said in a statement.

The bill’s signing is a significant achievement for Biden, who has long spoken of the country’s duty to care for its veterans after they return home. He has occasionally invoked the 2015 death of his son Beau of glioblastoma while wondering whether that cancer was linked to his son’s exposure to burn pits during his service in the Iraq War. In his first State of the Union address, Biden called on Congress to pass burn pits legislation.

At Wednesday’s bill signing ceremony, Biden was introduced by Danielle and Brielle Robinson, the wife and daughter of the late U.S. Army Sgt. 1st Class Heath Robinson, whose name is part of the longer, formal title of the legislation.

“I’m just in awe of your family’s courage,” Biden told the Robinsons. “I really mean that. Through the pain, you found purpose to demand that we do better as a nation. And today, we are.”

Danielle Robinson recalled how her husband’s return home from Iraq turned from a relief to “the biggest nightmare of our lives” after Heath Robinson was diagnosed with terminal Stage 4 lung cancer 10 years later.

“Ours is just one story,” she said. “So many military families have had to fight this terrible emotional battle. So many veterans are still battling burn pit illnesses. Today, too many have succumbed to those illnesses as well.”

President Biden hugs his grandson Robert Biden, son of the late Beau Biden, after signing the “PACT Act of 2022” during a ceremony in the East Room of the White House on Wednesday. Evan Vucci/Associated Press

The bill signing came nearly six years after Biden began pushing for the issue toward the end of his vice presidency. In a congressional conference room, he referred to a book he’d recently read – one that tied toxic burn pits to which his son Beau Biden had been exposed during his military service to his son’s subsequent death of brain cancer – and remarked, “Guys, I’m going to be the biggest pain in your neck as long as I live, until we figure out about these burn pits.”

Biden in the past has raised the possibility that his son’s cancer was partly the result of exposure to toxic chemicals during his service in Iraq and Kosovo, but he has also said that it is unclear. In a January 2018 interview with PBS’s Judy Woodruff, Biden said he thought burn pits played a “significant role” in his son’s cancer but added that “there’s been no direct scientific evidence that I’m aware of yet.”

“Because of exposure to burn pits – in my view, I can’t prove it yet – he came back with Stage 4 glioblastoma,” he said in October 2019 during a presidential campaign event.

But at the White House on Wednesday, he was far more direct. At one point, Biden briefly addressed young Brielle Robinson, pointing out that she was sitting next to his grandson, Beau Biden’s son.

“His daddy, lost to the same burn pits,” Biden remarked.

“Many of the fittest and best warriors that we sent to war were not the same,” he added later. “Headaches, numbness, dizziness, cancer. My son Beau was one of them.”

Biden pointed again to his grandson and other relatives in the room, adding, “To us and to many of you in the room, if not all of you, it’s personal. Personal.”

The signing ceremony in the East Room adds to a flurry of late-summer legislative wins for Democrats ahead of the fall midterm elections. On Tuesday, Biden signed a bipartisan measure to boost the domestic production of semiconductor chips. On Friday, the House is expected to pass a sweeping economic package known as the Inflation Reduction Act – a climate, health-care and tax measure – and send it to Biden for his signature.

The Pact bill enjoyed broad bipartisan support but encountered an unexpected delay last month after the stunning news of a deal between Sen. Joe Manchin, D-W.Va., and Democratic leaders on the Inflation Reduction Act. Shortly after that announcement, 25 Republicans who had recently supported the same bill switched their votes on the Pact Act in an apparent effort to deny Biden and Senate Majority Leader Chuck Schumer, D-N.Y., another legislative win.

Republicans tried for several days to contend that their blockage of the Pact Act had to do with a technical argument about which portion of the federal budget would fund $280 billion worth of new allocations for veterans’ health programs. But the GOP absorbed a series of political blows, led by comedian Jon Stewart and several prominent veterans groups, which in vigils and protests accused Republicans of using veterans as political pawns.

By the following week, many Republicans were ready to settle the matter, and on Aug. 2, the Senate overwhelmingly passed the bill on an 86-to-11 vote.

On Wednesday, Biden thanked advocates including Rosie Torres – co-founder of the nonprofit Burn Pits 360 – and Stewart for their work pushing for the legislation.

“What you’ve done, Jon, matters,” Biden said. “It really, really matters. You refused to let anybody forget, refused to let them forget. And we owe you big, man.”

At a bill enrollment ceremony Tuesday, House Speaker Nancy Pelosi, D-Calif., said it was an emotional achievement, and she indirectly criticized Senate Republicans for delaying the bill’s passage.

“It’s unfortunate that the Senate had to pull a stunt and not pass the bill on schedule, defeating the bill,” Pelosi said. “Thanks to the families who had all-night vigils to make sure the public was aware of what was happening again. Outside mobilization is what it takes to get the job done.”

The new legislation will expand VA health-care eligibility for veterans potentially affected by exposure to toxic burn pits – extending the period to enroll in VA health care from five years to 10 years for post-9/11 combat veterans, for example. It also will make it easier for veterans to qualify for VA services, and remove the burden of proof for veterans diagnosed with one of 23 ailments, including several types of cancer and respiratory illnesses. Survivors of veterans who died of one of those 23 illnesses also could be eligible for benefits under the new legislation.

The bill also expands toxic exposure research, requires that veterans enrolled in VA health care be regularly screened for toxic exposure-related concerns and provides for investments in VA health-care facilities across the country.

Veterans Affairs Secretary Denis McDonough vowed Wednesday that the VA stands ready to implement the Pact Act, and he encouraged veterans who might be eligible for care under the new law to visit VA.gov/PACT to learn more.

John Wagner contributed to this report.