An inspection of every "crumbling" school in Wales should be undertaken by the Assembly government to uncover hidden asbestos, a teachers' union said this week.
ATL Cymru is seeking support from Assembly members to lobby the government to take action following warnings that not enough is being done in Wales to control the "hidden killer".
Occupational health experts have said that teachers are disproportionately affected by asbestos- related diseases, which can lead to cancers such as mesothelioma. Many school buildings in Wales were built between the 1940s and 1980s, when asbestos was used extensively.
Earlier this week, lessons at Penyrheol Comprehensive in Swansea were disrupted after asbestos was uncovered in the school's annexe. Professional cleaners were called in when builders installing new windows found the potentially deadly substance.
Alan Tootill, Penyrheol's head, said the health risks were "minimal", but some pupils had been asked to stay at home because of a shortage of space.
"The annexe was built in the 1970s," he said. "The plan was to pull it down and rebuild it, but it would have cost around Pounds 3 or 4 million, so it stayed."
ATL Cymru is seeking a comprehensive audit of asbestos in schools and wants heads to receive training in dealing with asbestos hazards.
At its conference earlier this month, NASUWT union members also agreed to lobby for the removal of asbestos from all schools by 2012.
Tim Cox, the national executive member for south Wales, who proposed the motion, said there simply was not enough information about the extent or condition of asbestos in schools.
A spokeswoman for the Welsh Local Government Association said all local authorities complied with Health and Safety Executive guidance. "This guidance places a duty on councils to take reasonable steps to find asbestos and to take necessary action where the risk warrants it," she said.
"Asbestos removal where it is not needed is likely to raise the level of asbestos fibres within the air, therefore increasing people's exposure to risk."