Welsh school teachers are up to 10 times more likely to suffer from asbestos-related cancer than the general population. Even children could be susceptible, an expert has warned.
Fears of an "epidemic" of mesothelioma in Welsh schools were accompanied by warnings that the damage caused to the health of school staff could be "just the tip of the iceberg" - with the research not measuring the effect on children.
A conference on occupational health in Cardiff heard that official figures generally failed to take into account the difference between workers - such as builders - more likely to be routinely exposed to asbestos, and those who should never encounter it.
But occupational hygienist Robin Howie found that the adjusted figures showed mesothelioma rates were "far higher than should be expected" among teachers.
"And if the teachers are showing significantly high on the statistics, then what about the children?" he wondered.
"I think the teaching statistics are the tip of the iceberg. For every teacher exposed, then we have 20 to 30 children.
"I think there is a significant risk of mesothelioma in schools containing asbestos."
Asbestos was widely used in the construction industry between the 1960s and 1980s, and any building built or refurbished before 2000 is likely to contain the material.
The same conference heard the Health and Safety Executive describe asbestos-related disease as a "horror story" and an "epidemic".
Teaching unions last night demanded urgent action to tackle the "hidden killer" in Welsh schools.
Mr Howie revealed that the figures for female teachers were not as high as for men, but said this did not mean the problem was less severe.
The figures for females might be lower, he suggested, because of time off to raise families and because the figures looked at deaths to the age 75. As women generally live longer, their cause of death was less likely to be included.
"These are significantly higher figures than we expect," he added.
Dr John Osman, chief medical adviser of the HSE, said that 90,000 were expected to die in the asbestos-related disease "epidemic" by 2050.
Teaching, he added, was not in the list of top 20 at-risk occupation groups and there was a "debate" about the risk to schools.
He said the executive had been "preoccupied with asbestos for many years", creating a mesothelioma register, an asbestosis register and launching an awareness campaign.
Steve Coldrick, director of the HSE's disease reduction programme, said: "This is an absolute horror story, there's no getting away from it."
Rex Phillips, NASUWT Wales organiser, said after the meeting: "Robin Howie indicated that the minute there was exposure to asbestos, a school should be closed until the risk has been reduced to an acceptable level. Now we clearly know from past experience that that sort of thing doesn't happen in schools - they tend to try to manage around the continued operation of the school.
"Certainly, having been involved in a couple of situations involving asbestos at schools in Wales, I know that it does cause a great deal of concern and consternation among teachers, especially when you are told that it cannot be cured and they don't know the levels of exposure which can cause some of these illnesses and diseases."
He added: "Clearly we as a trade union would see the 'duty to manage' responsibility lying with the local authorities and the Welsh Assembly Government, rather than with individual schools, because schools can only manage up to a certain level of training and expertise.
"One of the things that the Welsh Assembly Government could do is that when they fund major capital projects within schools, they could make it a condition of the funding that the school or the college was able to demonstrate that it was appropriately exercising its duty to manage asbestos within its buildings."
An Assembly Government spokesperson said: "Locating and dealing with asbestos in schools, including removal if appropriate, is a health and safety matter for schools and LEAs.
"LEAs as the building owner and employer are required to comply with the Control of Asbestos Regulation 2006.
"These regulations impose a duty to manage asbestos on the building owners, which in the case of schools is the LEA."
The Assembly Government said the HSE's guidance document, Asbestos - An Important Message for Schools, was re-issued by the HSE in August 2006 and distributed to LEAs.
"When undertaking capital projects there are already regulations in place which local authorities must comply with in terms of managing asbestos."
Emma Corfield, who is an asbestos surveyor and consultant, said many employers fear that if they tell their employees of the risks, it would cause panic.
"But employees have a right to know where the asbestos is in their building," said Ms Corfield, managing director of Abergavenny-based Core Surveys.
"A management plan should be carried out in every workplace. This should include a register of asbestos on the site and the risks, and this should be a live document which is regularly updated.
"One year when the asbestos is inspected it may be contained and quite safe but its condition could deteriorate over time so regular inspections are important.
"Every person who comes into a school building, especially those who are carrying out work, should have sight of the management plan before they enter the site. It should be on the reception desk.
"But I know many teachers who say they have never seen this plan. Having worked in every type of workplace from schools, police stations to fire stations, I have never found one management plan that works."
Every school has a duty to manage its asbestos plan under the Control of Asbestos Regulations which came into force in 2002, Wales Online reported.
"The problem we have is a lack of awareness despite the fact we are talking about the biggest epidemic that has hit the UK in terms of occupational health."
But Ms Corfield said that while there are real dangers and every person is likely to have inhaled asbestos fibres during their life, there are many factors which will work together to determine whether they die from this exposure.
"I explain to people that in everyday life there are many risks," she said.
"Every time we get into our cars we take a risk.
"Some people could drink a bottle of gin a day and smoke 60 cigarettes and live a long life while others could not sustain that lifestyle.
"The same is true of asbestos exposure. There are genetic factors which have to be taken into account. There is also the length of time that it may take for any cancer to develop and some people will die of something else before that happens."