“When I was in the Air Force, they preached all the time: ‘Do the right thing. Integrity first. Service before self. Excellence in all we do’,” said Aaron Weed, a 22-year veteran who is now Oscoda’s town supervisor. “This is not the Air Force that I was a part of,” he continued. “The side of the Air Force that I am seeing is just disgraceful.”

Blood testing has emerged as a sticking point. Specifically, a growing movement of veterans and others, united in advocacy groups with names like Fountain Valley Clean Water Coalition and Need Our Water, are asking the military test their blood for the chemicals, hoping to bring results to their doctors or use them in lawsuits.

Their requests have been denied, and the military says that too little is known about the substances to make the results useful. Instead, it will pay for the C.D.C. to start yearslong population-based health studies in some communities.

“They don’t want to know,” said Cindi Ashbeck, 56, a veteran who worked out of Wurtsmith Air Force Base in Michigan. “It’s not being addressed, because you open that can of worms, and you’ve got an Agent Orange thing on your hands.”

PFAS are a broad class of chemicals developed in the 1940s. Because they repel grease and water, they have been used across industries for decades, often to prevent stains. They are placed in a dizzying array of products: food packaging, nonstick pans, clothing, furniture. They are also used to extinguish fires where petroleum-based explosions pose a danger.

But the chemicals move quickly through the earth and into water, where they persist indefinitely. Some scientists have deemed them “forever chemicals,” and over the last two decades, a growing body of research has shown that the compounds meant to help us are likely hurting us.