Fairfax County Executive J. Hamilton Lambert, responding in the first public forum about the discovery of naturally occurring asbestos in a prime development corridor, said yesterday the problem was no health threat and assailed news reports as exaggerated.

Lambert was asked about the asbestos during the County Board of Supervisors meeting, which also addressed radon detected in county schools.

On both fronts, Lambert said the environmental problems did not appear dangerous, and said he would release information on Thursday about the asbestos found in the county.

"From my humble opinion, I think this has been blown out of proportion dramatically," Lambert said in response to questions from Supervisor Elaine McConnell (R-Springfield). " . . . As far as I can determine, it is not a significant problem that cannot be managed."

Officials in this booming county have discovered that almost 7,000 acres near Fair Oaks Mall could be embedded with pockets of asbestos, a cancer-causing substance. They said they have identified airborne fibers at two construction sites, Fair Oaks Commerce Center near Waples Mill Road and Rte. 50, and Braddock Park High School on Union Mill Road off Braddock Road.

The asbestos is in a rock formation that runs through the west-central portion of the county, where a number of commercial and residential construction projects are under way or planned, including the Little Rocky Run subdivision, officials have said.

County officials, including Lambert, have characterized the asbestos problem as not unique to Fairfax. In letters mailed last week to three state environmental regulatory agencies, seeking guidance, the director of the county's Department of Environmental Management Claude Cooper wrote that the asbestos is likely to occur in 56 Virginia counties that are underlain with greenstone bedrock formations.

But some experts are skeptical of the county's assertions that the problem is a statewide issue.

The actinolite asbestos in Fairfax was discovered in the Piney Branch rock formation, which spans roughly 10 square miles, snaking from Miller Road, about two miles north of Fairfax City, and ending about eight miles southwest of Fairfax City.

While the greenstone is common, the band of rock specifically in Fairfax has a particular geological history that has caused the asbestos to form, according to Malcolm Ross, a research mineralogist for the U.S. Geological Survey, part of the Interior Department.

"They're just speculating because some rock down there is green," Ross said.

After the board's executive session, Supervisor Martha V. Pennino (D-Centreville) sought answers from Lambert about the asbestos problem, prompted she said by reporters' questions.

"It concerns all of us that there is a perception that there is something being kept from the board and from the public," Pennino said. "This is what we're trying to overcome . . . . Can you say there is no suppression of information from the board or the public?"

"Would you clarify suppression?" Lambert asked.

"Withholding of information," Pennino said.

Lambert replied that there has been "no purposeful withholding of information from this board."

The county executive said his staff did have information that "has not been transmitted to the board." Lambert said in an interview afterward that he wanted to gather the complete picture, rather than releasing information in a piece-meal fashion.

On the issue of radon, the supervisors directed the school board to continue monitoring the school sites where the gas has been detected and to take corrective actions where necessary.

Potentially dangerous levels of radon have been found at five Fairfax schools. At five additional schools, a first round of testing detected unhealthy amounts of radon, but a second measurement found the gas at a level not considered dangerous, results released last week by the Fairfax County Federation of teachers showed.