A Bel Air elementary school was closed yesterday after authorities found elevated levels of airborne asbestos in one of its two buildings, school officials said.

Homestead-Wakefield Elementary was to reopen today after school officials received air test results yesterday.

The asbestos was discovered Tuesday after crews removed ceiling tiles Monday night to install an air-conditioning system in the main lobby of the Wakefield building, said Don Morrison, Harford County public schools spokesman. Pipes above the ceiling tiles were lined with asbestos, which is commonly found in older buildings.

"When the tiles were removed, it disturbed what had been dormant fibers," said Morrison, referring to asbestos residue from the pipes. "When we discovered what had been done, we brought in an industrial hygienist. We did have levels of asbestos fibers above the allowable limit."

Federal guidelines require less than 70 structures per square millimeter, which is a measurement of asbestos fibers in the air. Two of the three air tests conducted Tuesday indicated that the area had 82 and 104 structures, Morrison said.

According to the U.S. Environmental Protection Agency, levels higher than 70 structures per square millimeter are not an immediate health threat. But longtime exposure to and inhalation of airborne asbestos fibers have been linked to respiratory diseases such as lung cancer, asbestosis and mesothelioma.

"There's no need to get upset and worried about short-term exposure, although it's something you want to avoid and no one should be happy about," said Patrick Breysse, an environmental health science professor at the Bloomberg School of Public Health at the Johns Hopkins University.

Breysse said closing school because of asbestos is uncommon.

"In most schools, they know where the asbestos is and know an asbestos management plan to make sure renovation plans don't disturb it," he said.

Workers decontaminated the building Tuesday night, and additional air tests were conducted yesterday, Morrison said.

"We're working to clear the air of any fibers and to make sure we wipe down the surfaces to make sure the tiny fibers are cleaned up," Morrison said.

According to the EPA Web site, the federal agency does not require schools to remove asbestos but requires schools to manage the materials and to undergo inspections every three years.

"In some cases, removing [asbestos] is very expensive and if it's not done right, it can make the situation worse," Breysse said.

In some cases, it is better to leave the asbestos alone as long as there is no risk of exposure and maintenance crews are aware of where it is, he said.

Morrison said the pipes that contain asbestos were lined with heavy plastic yesterday.

Wakefield, which was constructed in 1958, houses classrooms for pre-kindergartners to second-graders. A separate building, Homestead, contains classes for the school's third- through fifth-graders.

The Homestead building could not hold the 919-student body yesterday, so the entire school was closed. While students stayed home, teachers held staff meetings and addressed parent concerns at the Wakefield building, Morrison said.

madison.park@baltsun.com