Perchlorate is a pollutant from munitions used for decades at the 75,000-acre weapons-testing facility. In the past two years, the chemical has shown up in all 11 of Aberdeen's city wells.

Only by blending water from the most contaminated wells with flows from those with just trace levels has the city kept perchlorate concentrations in "finished" drinking water below 1 part per billion (ppb). That's the point at which the state warns of health risks.

The city of 13,500 people also buys 500,000 gallons of clean water a day from the county.

Now city officials say they need to spend $250,000 to install filter systems on the most tainted wells.

But the Pentagon refuses to clean up perchlorate at Aberdeen and dozens of other sites nationwide. It's part of a battle with the EPA over how much of the chemical can safely be left in soil and water.

The dispute highlights a Defense Department push to take regulatory fights into the laboratory. State and federal environmental agencies are using new scientific studies to make a case for tighter limits on military pollutants, which would add billions to Pentagon cleanup costs. At the same time, the armed services are enlisting their own scientists and funding research to challenge those studies. (Related graphic: An in-depth look at military bases' cleanup efforts)

The big battles involve perchlorate and trichloroethylene, or TCE, a solvent used in military vehicle maintenance. The EPA's latest studies say health risks from exposure to both chemicals are higher than previously believed. After the Pentagon complained to the White House about the studies, the EPA decided that its research, already checked by independent panels, should go to the National Academy of Sciences for more study.

Alex Beehler, assistant deputy undersecretary of Defense for environment, says the military wants to be "a responsible player" in regulatory debates. Diving into the science, he says, "is one small but appropriate way we can do so."

Environmental groups disagree.

The Pentagon "is using the White House to come from the top," says Lenny Siegel of the Center for Public Environmental Oversight in California. "Rather than having the same standing as states, communities, industry groups or anyone else, they're above everybody."

The EPA has not complied with Freedom of Information Act requests filed by USA TODAY seeking copies of its communications with the White House and Pentagon.

EPA research chief Paul Gilman says the agency was not forced to go to the National Academy of Sciences. "In both instances," he says, "it was our idea."

No one owns more properties contaminated with perchlorate and TCE than the Pentagon, federal records show. And the military is leading the charge against efforts to clamp down on the pollutants:

•Perchlorate. The EPA's disputed risk study finds that small doses raise risks of thyroid problems and related ills in fetuses and infants. The study suggests that 1 ppb of perchlorate in drinking water — the equivalent of a half-teaspoon in an Olympic-size swimming pool — is a safe limit for pregnant women and children.

The armed services have argued that levels up to 200 ppb are safe.

Col. Daniel Rogers, an Air Force environmental lawyer, told the National Academy last year that the EPA's study is "biased ... and scientifically imbalanced" because it ignores other research that has found no proof of ill effects among people exposed to perchlorate.

The academy review means the EPA probably won't set pollution limits on perchlorate before late 2006, officials say. Meanwhile, some states are considering their own limits of under 10 ppb in drinking water.

•TCE. The EPA's new risk study suggests a need for tighter limits on contamination. It concludes that TCE vapors from contaminated soil and groundwater can seep into buildings and boost cancer risks.

The EPA's independent Science Advisory Board checked the study and "was largely supportive of the approach and conclusions," says review leader Henry Anderson, chief medical officer for Wisconsin's Division of Public Health.

But the Pentagon says the study is "based on the ardor and hypotheses of the EPA authors, rather than sound scientific evidence."

Some states already are tightening their TCE regulations, but the EPA is waiting to adjust federal rules until the academy finishes its review — in 2007.

The groundwater feeding Aberdeen's well fields has perchlorate levels up to 24 ppb, but officials at the proving ground are bound by the Pentagon's freeze on cleanups.

"Generally, we'd be doing something to address it at this point, with it showing up in the wells," says Ken Stachiw, the base's environmental restoration chief.

The EPA could order a cleanup if the perchlorate posed a "substantial hazard" to drinking water. But the agency has resisted staff suggestions to do so because perchlorate levels in Aberdeen's "finished" water haven't exceeded 1 ppb.

"Nobody is standing up for the community," says Glenda Bowling, a local activist.

"We could wake up one day and it could be 20 parts per billion in that water, and we wouldn't be able to drink it."