In this file photo from 2004, Principal Marta Palacios, left, and custodian Ricky Kelly in an empty 60 student class room that had the ceiling tiles removed for asbestos abatement. (James M. Thresher/The Washington Post)

When the Ocean View school district in Orange County, Calif., began to modernize its facilities last year, school officials and taxpayers got an unwelcome surprise.

Workers found asbestos in 11 buildings, triggering a costly and disruptive effort to remove the carcinogen. Three elementary schools had to be shuttered for the year, displacing about 1,700 children. One school will reopen at the end of this month, but the other two remain closed as work continues. The school district had to take out a loan to help cover $15 million in costs.

“Everyone has asbestos, but they don’t want to deal with it,” said Gina Clayton-Tarvin, president of the Ocean View school board. “To abate it is absolutely astronomically expensive.”

Schools built before 1980 are likely to contain asbestos, a fibrous mineral that was widely used as a flame retardant in insulation, roof shingles, tile floors and other construction materials.

Asbestos was heavily used in schools built between the 1940s and the late 1970s, when the federal government banned its use in new construction. Asbestos is not considered a health risk when it is stable and undisturbed. But if asbestos deteriorates and its microscopic fibers become airborne, it can increase the risks of lung cancer, mesothelioma and other lung disease.

The Environmental Protection Agency estimated in 1984 that 15 million students and 1.4 million teachers and school personnel were at risk of exposure to airborne asbestos, based on a sampling of 2,600 public and private schools. Two years later, Congress passed legislation requiring public and private schools to regularly inspect their buildings for asbestos, clean up any hazards and publicly report their actions.

But no one knows how many schools now contain asbestos.

Sen. Edward M. Markey (D-Mass.), the ranking Democrat on the Senate subcommittee that oversees chemical policy, said it is unclear whether schools are complying with the law or a government agency is enforcing it.

“If there are gaps in enforcement, legislative or other reforms may be needed to ensure schools are free from this toxic hazard,” Markey said. He suggested that schools may also need government help to pay for asbestos abatement.

A spokeswoman for the EPA said the agency is mostly responsible for enforcing the federal law, but some duties fall to the states.

Markey and Sen. Barbara Boxer (D-Calif.) wrote to all 50 governors in March to ask how many of their school districts are following the requirements of federal law. “As implementation of this law approaches the thirty-year mark, the extent of asbestos hazards remaining in schools across the nation is largely unknown,” they wrote.

Every governor responded, but the answers indicated that the federal law was not being followed uniformly, a Markey spokeswoman said.

“We don’t have any indication that the government is doing its job to make sure measures are in place,” said Sonya Lunder, a senior analyst at the Environmental Working Group, an environmental group whose lobbying arm, the EWG Action Fund, has launched a public awareness campaign regarding asbestos.

In Ocean View, district officials knew that asbestos had been sprayed on metal girders that were above ceiling tiles in several schools, and maintenance workers had been inspecting facilities every six months, looking for signs of asbestos deterioration, school board president Clayton-Tarvin said.

But when the board decided to modernize 11 schools, no one raised the issue of asbestos remediation, she said. As the work got underway, the contractor delivered the bad news, she said.

The state or federal government ought to help school districts with remediation costs, Clayton-Tarvin said. Instead, local taxpayers were on the hook.

“We spray this stuff on because it’s safe,” she said, referring to former beliefs about asbestos. “Then they find out it’s not safe. Really, whose responsibility is it? I don’t think it’s the school district. We’re trying to educate kids today. We shouldn’t be responsible for paying for past sins.”