PUPILS and teachers from the Lanarkshire school at the centre of a cancer row should be tested for toxins, a public health expert has said.

Professor Andrew Watterson, of Stirling University, said the independent safety review commissioned by the Scottish Government into the Buchanan and St Ambrose high schools site in Coatbridge amounted to a "paper exercise", and that biological and environmental testing should also take place.

It came as members of the NASUWT teaching union began a week-long walkout from Buchanan High, where four teachers - including three from the same corridor - have been diagnosed with bladder cancer since it opened in 2012.

A male pupil has also gone blind and reportedly tested positive for unusual levels of arsenic, a chemical also known to increase the risk of bladder cancer.

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However, an information leaflet sent out last week by North Lanarkshire Council to parents and staff stressed that there are two forms of arsenic - toxic and non-toxic.

The latter occurs naturally in foods such as fish, shellfish and rice and can result in a temporary but harmless rise in blood arsenic levels.

The council said there had been no cases involving the toxic form of arsenic from heavy metals, and that school attendance levels did not indicate higher than normal sickness absence.

Yesterday First Minister Nicola Sturgeon vowed to do "everything necessary" to allay health fears, but said it was up to the review team to decide whether to carry out extra tests.

Prof Watterson said: "The review will not answer what's gone on. It's going to be a paper exercise where they look at what the council said they did, then what the health board said they did.

"But it still leaves a lot of questions up in the air if monitoring has not taken place, either biological in the form of blood, hair, and nail samples, or environmental."

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The schools were built on a former landfill site previously used for dumping domestic and industrial waste, and initial ground-testing in 2010 detected known carcinogens such as arsenic and benzo-a-pyrene.

It was given the all-clear in 2012 following remedial work including laying 2ft of top soil and the council says the site poses no threat to health.

It insisted that since the school has been open less than 10 years, there is no chance that the teachers' cancers could have been caused by exposure to anything at the site.

However, Prof Watterson pointed to a major study into bladder cancer in the US which found a minimum 'latency period' - the time lapse between exposure to carcinogens and disease onset - of four years.

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There has also been concern that high levels of copper were found when the water supply from two school taps turned blue last year, but since November routine monitoring of the water supply found it has met safe drinking standards.

Although consuming water contaminated with copper can cause problems such as sickness and diarrhoea, copper from drinking water is not believed to cause cancer.

However, Prof Watterson said exposure to other toxins could have occurred through inhalation and said air monitoring should also take place.

Ms Chris Keates, General Secretary of the NASUWT, added: “While the independent review promised by the Scottish Government is a welcome development it still does not commit to a full comprehensive site survey which tests the water, air, soil and fabric of the building."

A spokeswoman for NHS Lanarkshire said there were no grounds to carry out checks such as blood tests.

She said: "The public health assessment is that there is not a risk to health from arsenic in relation to attending the schools.

"To date, there have been no identified cases of illnesses caused by elevated heavy metals.

"It would not be appropriate to test where a risk is considered not to exist."