EDUCATION Secretary John Swinney is to announce an imminent clampdown on cancer-causing processed meat in schools following a campaign by the Herald on Sunday.

Swinney is expected to back maximum legal limits for meats such as ham and bacon at lunch times, and support a restriction on the use of products which contain nitrites.

Meanwhile, Glasgow city council - the largest local authority in Scotland - has confirmed its schools are planning to go nitrite free by the end of the year.

A World Health Organisation (WHO) report from 2015 placed processed meat in the same carcinogenic category as asbestos and tobacco.

Experts found that a 50g portion eaten daily - the equivalent of two rashers of bacon, or a single sausage or hot dog - would increase the risk of bowel cancer by 18%.

Herald on Sunday campaign: time to dump 'nitro' meat from schools and hospitals

The health risk occurs when nitrites - a preservative which helps turn meat pink - is heated and produces cancer-causing nitrosamines. Governments across the world are facing calls for a ban on nitro meat.

This newspaper launched a campaign after it emerged that a majority of councils, which run schools, offer processed meats with nitrites. Ham is the most commonly used staple, while bacon, corned beef and pepperoni are also used.

We called on the Scottish Government to rid school meals, of which around 360,000 are served every day, and hospital food of nitro meat and embrace healthier alternatives.

All Holyrood’s opposition parties - the Tories, Labour, the Lib Dems and Greens - supported the move, which means a majority exists in Parliament for action.

It is understood Swinney will this month announce an overhaul of the food and drink regulations in schools, which were introduced over a decade ago.

It is expected the changes will be based on a report that was issued by a Government-commissioned working group.

The report, which Swinney has since consulted on, explicitly referenced earlier research which highlighted the link between red and processed meat and colorectal cancer.

READ MORE: Parent groups urge action on processed meat in schools

Experts on the group recommended that no more than 100g of red processed meat should be given to pupils over the course of the school week, and backed a weekly maximum of 130g for secondaries.

These weekly limits are under the 50g daily amount mentioned in the 2015 WHO report and would have full legal force if they became statutory regulations.

The group also proposed that the provision of red and red processed meat is “not permitted outwith the lunch in primary schools”.

Nitrites were not mentioned in the report, but Swinney’s crackdown is expected to include this cancer-causing chemical.

Scottish Labour MSP Monica Lennon said: "Scottish Labour will warmly welcome any moves towards reducing the availability of harmful nitro meats in our schools.

“Given the strong scientific evidence linking the consumption of processed meats and risk of bowel cancer, it’s sensible to adopt a cautious approach – which is why Scottish Labour backs a ban on nitrite meat being served in schools and hospitals.

“This is not about stopping people from eating what they want – nitrite free meat options are available, and it would be a welcome move for this to be introduced as the norm rather than the exception.

“Local authorities like North Ayrshire have already taken the decision to secure nitrite free options across the full menu – and Scottish Labour will continue to call on the SNP Government to follow their lead.”

A Scottish Government spokesperson said: “Providing healthy meals for children and patients is vitally important.

“We expect schools to serve healthy and nutritious food. Having considered the responses to our recent consultation on nutritional school food standards that proposed introducing a maximum level for red and red processed meat – including those where nitrites have been raised as a concern – and we expect to publish a report by the end of June detailing the changes to be made to school food and drink legislation.”

READ MORE: Top scientist Professor Denis Corpet backs public health campaign on 'Stupid' nitro-meat

Glasgow council, which is SNP run, initially told this newspaper that no processed meat with nitrites are used in the city’s schools.

However, while this is true of primary school menus, it has since been confirmed that nitrites are present in some of the bacon and ham sandwiches on offer in secondaries.

The council said: "Catering and Facilities Management are having discussions with their suppliers and they are planning to be able to say that there will be no nitrites in any of the menus offered in Glasgow schools by the end of the calendar year."

Bailie Siddique, who is Labour’s education spokesperson on the council, welcomed the move.

Soryia Siddique said: "I am pleased that Glasgow City Council education department is now removing nitrites from food menus.

“Prevention is better than cure, it is documented that nitrite combines readily with secondary amines to form carcinogenic nitrosamines. Hence removal of nitrites from Glasgow school menus is welcomed and will go towards reassuring children and families that health and wellbeing is a priority.”

However, the Scottish Government last week appeared to be less willing to back changes in hospitals.

Asked by Tory MSP Liam Kerr about nitrite-meat, SNP Minister Joe Fitzpatrick replied: "All hospital food must meet national food, fluid and nutrition standards. Under the NHS Scotland procurement framework, all suppliers must adhere to all relevant requirements, including those under the Food Safety Act 1990, as amended, and Scottish, United Kingdom and European Union food safety regulations."

Pressed on whether he agreed nitrite-meat should be "nowhere near" hospital menus, Fitzpatrick replied: "Liam Kerr might want to speak to some of the high-quality food producers in Scotland that use nitrites, which are in line with food safety rules and guidelines. On this issue, Scotland has led the UK by setting a minimum standard for our hospital food, which all has to meet the food, fluid and nutrition standards, as I have said.

"They take account of the latest scientific advice on the amount of red and processed meat that can be consumed for a healthy balanced diet, which is already no more than 70g of red and processed meat in a day."