Prince William County maintenance officials are nearing the completion of an asbestos removal program that has eliminated the fibrous material from seven buildings, county officials said this week.

Southern Maryland Renovations, which was awarded the contract for the job by the county, is expected to begin removing asbestos from the Prince William County Police Department's Manassas headquarters building before the end of the year. The police office is the eighth and final building to be cleaned up, said county operations and maintenance chief, Bob Weiss. Asbestos was removed from the seven other buildings by Falcon Associates Inc., of Bristol, Pa., Weiss said.

The use of asbestos in friable building materials -- those materials easily crushed or pulverized, such as fireproofing material and insulation -- was banned by 1978. Some non-friable material, such as floor tiles, contained asbestos until the mid-1980s, said Wayne Morgan, an engineer with BCM Engineers Inc., which consulted with the county on the asbestos testing and removal.

Asbestos was first identified in the structures during testing of 29 buildings in late 1987 and early 1988, officials said.

Morgan said samples were taken from building materials and ceiling and floor tiles and tested in a laboratory under a microscope to determine whether building materials contained asbestos, the prolonged inhalation of which has been linked to increased incidence of lung cancer, and what levels were present.

Air monitoring also was performed to determined whether asbestos fibers were being released into the air, Morgan said. "The information said we were below any OSHA requirements," he said.

The Occupational Safety and Health Administration has set a standard of 0.1 fibers per cubic centimeter in the air before the use of protective gear is recommended. The maximum recommended exposure is 0.2 fibers per cubic centimeter, Morgan said.

Tests determined that the level in the eight county buildings measured between 0.004 and 0.006, Weiss said. He said the county opted to remove the asbestos, at a cost of $240,000, as a safety precaution.

"It makes it difficult to maintain a building with asbestos in it because any work in the area would release the material," he said.

Morgan cited the example of removing ceiling tiles containing asbestos in explaining the difficulty of working around the material. Although the tiles might not release fibers during normal working hours, if the tile is lifted for work purposes, asbestos fibers exceeding OSHA requirements might be released in dust particles into the air, Morgan said.

But sometimes removal of the material is more trouble than it is worth. The county opted to leave some asbestos-containing floor tiles in place because they don't pose a health threat and removal would be expensive and would mean complicated procedures, Morgan said. The county's cleanup program affected about 200 county employees, some of whom were relocated to trailers while workers removed asbestos from their offices.

The second floor of the Prince William County Police Department's Gar-Field substation was evacuated for two weeks while asbestos-containing ceiling tiles were removed.

During the removal, some police officers grumbled about the inconvenience of being moved into trailers temporarily while the work was going on.

The Department of Health office building adjacent to the Gar-Field police substation also was temporarily evacuated, Weiss said.

Asbestos was intermixed with asphalt in the roof, originally installed as a fire retardant. Asbestos-containing pipe and boiler insulation was also removed, Weiss said.

The county police building in Manassas contains asbestos in the ceiling tile and pipe insulation, so it will require transferring employees to trailers while the building is "encapsulated." The process of encapsulation, which keeps the asbestos fibers contained, entails wrapping the inside of an asbestos-containing building in plastic to prevent the fibers from moving around in the air. Filters and special air cleaning agents are used to keep the fibers from moving around outside the containment area, Weiss said.