RADIOACTIVE air pollution has doubled at a Scottish nuclear base – sparking cancer warnings from campaigners.

Emissions of the radioactive gas, tritium, at Royal Naval Armaments Depot Coulport, where nuclear warheads are stored rose between 2018 and 2023 from 1.7 billion to 4.2bn units of radioactivity, The Ferret reports.

Campaigners say tritium is “very hazardous” and can increase the risk of cancer if inhaled – but the Scottish Environment Protection Agency (Sepa) insists the levels are well within safety limits.

The Ferret reports that the Ministry of Defence (MoD) has refused to say what has caused the increase, though tritium is known to leak from ageing nuclear submarine reactors, and is also an essential component of nuclear bombs.

Concerns have previously been raised about the state of Britain’s ageing nuclear fleet.

The figures, revealed in Sepa’s Scottish Pollution Release Inventory, also showed that Faslane has discharged liquids contaminated with tritium into the Gareloch, amounting to a total of over 50bn units of radioactivity from 2018 to 2023.

The discharges peaked at 16.6bn units in 2020.

Sepa was previously found to have changed the rules to allow some tritium-contaminated waste to be discharged into the Gareloch.

“Low levels” of tritium had been discovered in waste, sewage and ballast water from submarines.

Sepa agreed a “minor variation” to radioactive waste regulations to allow the continued treatment and disposal of the effluents.

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Dr Ian Fairlie, an expert on radioactivity in the environment and a former UK government advisor, told The Ferret the pollution was “worrying”.

He said: “First, they are large, more than four billion becquerels per year; second, they are steadily increasing; and third, they are of tritium – which is very hazardous when it’s inhaled or ingested.

Dr Fairlie, now the vice-president of the Campaign for Nuclear Disarmament, said that the discharges at Faslane were also concerning, adding: “Any dose of radiation is hazardous to some degree, so that these discharges – especially of tritium – are disquieting.”

Scottish CND chair Lynn Jamieson (above) said: “Governments use the idea of ‘safe levels’ and ‘acceptable risk’ but scientists agree that any exposure to ionising radiation poses some health risk.”

She added: “Children and pregnant women are particularly vulnerable and the risk of cancers increases as exposure increases. No human-made increase in ionising radioactivity in our environment is good for human health and all increases should be challenged.”

And the Scottish Greens also questions assurances that radioactive emissions were “safe”.

Party co-leader Patrick Harvie said: “It is preposterous that Sepa and MoD claim that the emissions are within safe, permitted limits when they themselves are changing the goalposts to further contribute to the toxic, moral failing that has plagued Scotland’s shores since the 1980s.”

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The problem may get worse in the future, warned Pete Roche, the policy director of the Nuclear Free Local Authorities group, because Trident submarines are “getting older”.

Sepa was criticised for allowing radioactive waste to be “dumped in the Clyde”, with the Nuclear Information Service’s director David Cullen saying: “When tritium was found to be leaking into waste effluent, that should have set alarm bells ringing, and Sepa should have been demanding that the MoD track down the source and prevent it.”

Sepa said that “letters of agreement” governed the discharge of radioactive waste, adding: “All discharges have been within the limits set.”

The public body said that variation was related to “operational programmes”, which were a matter for the MoD.

An MoD spokesperson said: “All waste discharges, including gaseous elements from His Majesty’s Naval Base Clyde and Coulport, are in compliance with the conditions agreed between the MoD and Sepa.”