Unsafe levels of cancer-causing radon gas detected at 16 UK prisons
Unsafe levels of cancer-causing radon gas have been detected in 16 prisons, and a further 33 prisons are being investigated by the Ministry of Justice (MoJ).
HMP Dartmoor in Devon was closed in 2024 after radon levels of up to 10 times the recommended limit were recorded in some areas. Hundreds of former prison staff and inmates have signed a class-action lawsuit against the Department of Justice seeking compensation for their exposure.
Now Independent HMP can reveal that Bedford, Channings Wood, Downview, East Sutton Park, Exeter, Hollesley Bay, Leicester, Lincoln, Lindholme, Parc, Portland, Stafford, The Verne, Usk and Wealstun measured unsafe levels deemed “above action” by authorities.
Radon is a colorless, odorless, radioactive natural gas formed as a result of the decay of small amounts of uranium in rocks and soil. It can accumulate in enclosed spaces and be controlled through ventilation, but it is known to increase a person’s risk of lung cancer, with more than 1,100 deaths from the disease attributed to radon each year in the UK, according to the Health Safety Agency. Symptoms of radon poisoning include wheezing, fatigue, and a bloody cough.
By law, mitigation measures must be taken to reduce radon exposure in workplaces if levels are shown to exceed an annual average of 300 bq/m³. According to UK health safety agency guidance, this amount is reduced to 200 bq/m³ for sleeping areas such as prison cells.
Measurements above action levels of radon gas were taken at 16 sites with unsafe levels, as well as at a separate site within HMP Lindholme near Doncaster, at 16 probation sites in London, the South East, the South West, Wales, the North West, the East Midlands and the east of England.
The number of areas measuring high in radon was revealed in meeting minutes recorded by the Prison Officers Association (POA) in early 2024. The Justice Department said this week that a small number of 33 investigations sparked by alarming radon levels are still awaiting final signature or under review.
A prison service spokesman said they were “taking steps to actively reduce the risk posed by radon in line with health and safety regulations”.
New documents released this week under freedom of information laws show high levels of radon gas were measured at HMP Exeter in 2020. Radon levels in wing D of the category B men’s prison were given a seasonally adjusted result of 2,750 bq/m³ in winter 2020; That’s nine times the legal limit.
Later, in 2022, a report was carried out by CERAP UK experts on the high levels detected two years ago. The report dated August 2022 states that the company recommended the suspension of activities and settlement in the affected areas.
Further measurements from late 2024 to early 2025 showed radon levels in some parts of the prison were above 900 bq/m³, while another area measured 1,235 bq/m³.
Another risk assessment for the prison, carried out in May 2025, recommends banning prisoners from areas where radon concentrations are higher than 300 bq/m³.
Approximately 20-25 current inmates contacted Kesar & Co, the law firm handling the legal case at HMP Dartmoor, over potentially harmful exposure to radon at HMP Exeter. A similar number of people contacted the firm about the whistleblowing incident at Doncaster prison HMP Lindholme.
Kesar & Co solicitor Inaam Barkatoolah said: “The results from Exeter and Lindholme are quite worrying. They show that there were periods when radon levels were very high in certain parts of the prison. As in the Dartmoor case, we have people complaining of symptoms of radon poisoning – wheezing, tiredness, bloody cough. They are even more concerned than some Dartmoor clients because some of them were already in prison. Before Dartmoor.”
“In Exeter and Lindholme it was very difficult for people to get any information. They were just told that there was radon in the prison and that it was being monitored.”
Lindholme results, released under FOI, show that tests carried out between 2019 and 2020 found excessive radon levels in the E wing of the prison. According to FOI data, high radon levels were measured again in 2023 in wings A, B, C, D and E, but these levels had decreased by 2025.
Following concerns about how radon was controlled at HMP Dartmoor, POA deputy general secretary Mick Pimblett said: “POA is working with HMPPS to ensure radon levels are monitored by facilities management in all prisons in radon-affected areas.”
Mr Pimblett added: “Where a prison is exposed to extreme levels the POA is satisfied that appropriate risk assessments are carried out and controls are in place.” He said the union was “delighted that staff were informed of the reductions and monitoring arrangements”.
A prison service spokesman added: “We are closely monitoring the effectiveness of these mitigation measures.”
