FOUNTAIN, Colo. — Volk Sanders burst into this world on June 7, a six-pound fuzz-headed ball of joy and his mother’s first child.

Days later, Volk’s mother learned that the well water she had consumed for years had been laced with chemicals that the Environmental Protection Agency associates with low birth weight, cancers, thyroid disease and more.

The aquifer that courses beneath this community in the shadow of five military installations showed traces of perfluorinated chemicals at up to 20 times the levels viewed as safe, environmental authorities said. A sudsy foam used for fighting fires on military bases was probably responsible, according to the Air Force, with the contamination perhaps decades old.

“I’m very angry,” Volk’s mother, Carmen Soto, 20, said at a packed community meeting on July 7. Volk had struggled to gain weight, she said, and she wondered if that was related to the contamination. “They’ve known about this for how long, and they’re just telling us? I drank water throughout my pregnancy. What is that going to do?”

Fountain — named for a creek that once gave life to this southern Colorado town — is now part of a growing list of American communities dealing with elevated levels of perfluorinated chemicals, or PFCs, in their drinking water. In the last few months, PFC poisoning has upended municipalities around the country, including Hoosick Falls, N.Y., home to a plastics factory, and North Bennington, Vt., once home to a chemical plant.

Unlike in many of the other places, the contamination in Fountain and in two nearby communities, Widefield and Security, is not believed to be related to manufacturing. Rather, the authorities suspect that it was caused by Aqueous Film Forming Foam, a firefighting substance used on military bases nationwide.

Defense Department officials initially identified about 700 sites of possible contamination, but that number has surged to at least 2,000, most of them on Air Force bases, said Mark A. Correll, a deputy assistant secretary for environment, safety and infrastructure at the Air Force.

All of the nine bases that the Air Force has examined so far had higher-than-recommended levels of PFCs in the local drinking water. Four bases identified by the Navy were also found to have contaminated water. In some places, the contamination affects one household. In others, it affects thousands of people.

The bases are in Alaska, California, Colorado, Delaware, Michigan, New Hampshire, New Jersey, New York, Ohio, Pennsylvania and Virginia.

“It’s quite possible it will touch every state,” said Jennifer Field, a professor at Oregon State University and an expert on the chemistry of Aqueous Film Forming Foam. “Every place has a military base, a commercial airport, an oil refinery, a fuel tank farm.”

The Air Force has spent $137 million to assess the scope of the problem, and is spending several million more to treat water systems and provide alternate drinking-water sources. It does not have an estimate of how much cleanup will ultimately cost, though one official said it would “likely be quite large.”

“This has focus at the absolute highest level of the Air Force,” Mr. Correll said. “We take it seriously. We’re addressing it aggressively. The Air Force will take responsibility for its actions.”

The firefighting agent in question is a white substance often shot from a hose and used to extinguish fuel fires since about 1970. Aqueous Film Forming Foam was created by 3M at the behest of the Navy, which needed a way to stamp out fires on ships.

The foam was later adopted by airports, oil fields and municipal fire departments, becoming an integral part of the nation’s firefighting kit. It was often sprayed directly onto the ground during repeated training sessions on military bases.

It has probably saved hundreds of lives, including those of pilots in plane crashes.

The foam is laden with perfluorinated chemicals, an unregulated class of man-made chemicals that travel quickly in water and last for years in bodies and environments.

In the face of growing evidence of adverse health effects, the Environmental Protection Agency is considering whether to regulate the chemicals, which manufacturers have used for decades in everyday products like clothing, mattresses and food packaging. In May, the agency released a new health advisory on two of the best-known perfluorinated chemicals — PFOA and PFOS — suggesting that communities keep their water below 70 parts per trillion for the two combined.

Some who have followed the issue say the government has been too slow to act. “There are those who have argued it just became too big to regulate,” said Rob Bilott, an Ohio lawyer who has urged the E.P.A. to monitor the chemicals since 2001. “It just became such a massive potential issue because of how widespread these chemicals were.”

A spokeswoman for the federal agency, Monica Lee, said its response had evolved “as our understanding of how these chemicals affect human health has improved.”

In Colorado, Fountain, Widefield and Security were among 63 public water systems identified in May by the E.P.A. as having PFC-contaminated water. The communities, which have a combined population of about 60,000, sit in the shadow of the Rocky Mountains, and above an aquifer just south of Peterson Air Force Base. The military plays such a large role here that many refer to the base like an old friend, simply “Pete A.F.B.”

Fountain tested at twice the E.P.A.’s latest recommended level. Widefield tested at more than three times the guideline. And Security showed levels nearly 20 times the guideline.

The communities’ anger was evident on July 7, when an estimated 800 people crammed into two halls at Mesa Ridge High School to listen to a doctor, E.P.A. and Air Force officials, and others discuss the problem and their follow-up. PFCs cannot be boiled out of the water, they explained, and only certain filters remove them. The Air Force plans to spend $4.3 million to treat drinking water in the area.

“This is all I think about,” said Tanya Marcus, 38, who raised four children on Widefield’s water system. “I’m not so worried about myself. I’m worried about my kids and everybody else’s kids.”

Particularly worrisome for some was a state health report that compared cancer rates in contaminated areas with those in the rest of El Paso County. Kidney cancers were about 17 percent higher than expected, bladder cancers about 34 percent higher and lung cancers 66 percent.

A state health department doctor, Mike Van Dyke, pointed out that research had associated only one of those cancers — kidney — to PFC contamination, and that high levels of smoking and obesity in the area could explain the elevated numbers. “We don’t think this is a PFC effect,” he said, “but we can’t be sure.”

Utilities directors in the region have shut off many of the poisoned wells, and are pumping in water from elsewhere in the state, an expensive and temporary fix. Local officials have said some people’s water is now safe, while others’ is not. They urged caution, particularly for pregnant and breast-feeding women, but that has sown greater confusion. (The state health department has created a map to help people identify areas of risk.)

Ms. Soto, sitting in the bedroom she shares with the baby, Volk, said that she had switched to bottled water, but that she was breast-feeding and worried she was passing her exposure to PFCs to her son. Baby formula is not really an option, she said, as she works only part time at a Burger King that pays $8.75 an hour.

On recent Fridays, minivans and pickup trucks filled the sprawling parking lot of the St. Dominic Church, where a food bank passed out bottled water using money from a disaster fund.

On the morning after the community meeting, the first car showed up just after 5 a.m., hours before the handout began, its occupants anxious that the water would run out.