The San Joaquin Valley's air is now classified as healthy under the federal standard for dust and soot, the dangerous, tiny specks that can trigger lung problems.
The U.S. Environmental Protection Agency made the landmark announcement Thursday following two years of protests from environmentalists who say officials have simply ignored many violations.
Environmentalists sued the EPA in March after the agency waived several violations because of high-wind conditions in the Valley.
Arguments are supposed to be heard in the 9th U.S. Circuit Court in February.
Local air officials say the Valley -- 25,000 square miles from Stockton to Bakersfield -- has not violated the so-called PM-10 standard since 2003. It is the first completed cleanup of a major pollutant here since the 1990s.
The EPA's action Thursday means the Valley no longer faces PM-10 cleanup deadlines or possible federal sanctions, which include temporarily cutting off $2 billion in federal road-building funds.
But environmentalists say the EPA's approval is illegal because the agency should not have waived bad-air readings in Bakersfield and Corcoran over the past few years.
"There are literally dozens of exceedences that have been ignored," said attorney Paul Cort with Earthjustice, a nonprofit legal watchdog group in Oakland. "This is the Bush administration patting themselves on the back when people are clearly suffering." Federal, state and local air officials disagreed, citing Clean Air Act exceptions for natural events, such as excessively windy days.
Environmentalists say that if they prevail in the case, they may have a legal reason to force the EPA to rescind the Valley's new clean-air classification for PM-10.
Meanwhile, authorities will not shy away from stricter rules to hold down dust from industries and residents, said Seyed Sadredin, executive director of the San Joaquin Valley Air Pollution Control District.
"We have a maintenance plan in place for the next 10 years so there will be no backsliding," he said.
Sadredin said the PM-10 cleanup relied heavily on rules requiring farmers to water unpaved roads, make fewer passes over their fields with tractors and other similar measures. Fireplace regulations over the past several years also have helped, he said.
Sadredin added that if the district has even one bad reading in the future, the Valley will again be in violation of the standard.
EPA officials said they would push for stricter requirements on other major pollutants as well.
"In addition to the current controls, many additional reductions will be needed to attain the more protective PM-2.5 standard and the ozone standard," said Deborah Jordan, air division director for the agency's Pacific Southwest region.
Activists were not impressed, saying the EPA doesn't pay enough attention to the health problems created by the dust and soot.
"When I stop seeing Valley residents in the emergency room gasping for breath, then I'll pop the champagne," said respiratory therapist and Fresno resident Kevin Hamilton. "Until then, we'll see EPA in court."