Radon Gas Crisis: 16 UK Prisons Record Unsafe Cancer-Causing Levels
An exclusive investigation has uncovered that unsafe levels of cancer-causing radon gas have been detected at sixteen prisons across the United Kingdom, with a further thirty-three sites currently under investigation by the Ministry of Justice. This alarming discovery follows the closure of HMP Dartmoor in 2024 after radon levels were recorded up to ten times higher than the recommended safety limit in certain areas.
Prisons Affected and Legal Ramifications
The prisons identified with unsafe radon levels, deemed "above action" levels by officials, include HMP Bedford, Channings Wood, Downview, East Sutton Park, Exeter, Hollesley Bay, Leicester, Lincoln, Lindholme, Parc, Portland, Stafford, The Verne, Usk, and Wealstun. In response, hundreds of former prison staff and inmates have now signed up to a group legal action against the Ministry of Justice, seeking compensation for their exposure to the hazardous gas.
Radon is a colourless, odourless radioactive natural gas that forms when trace amounts of uranium in rocks and soils decay. It can accumulate in enclosed indoor spaces and is a known contributor to lung cancer risk. According to the Health Security Agency, radon exposure is responsible for more than 1,100 lung cancer deaths annually in the UK. Symptoms of radon poisoning include wheezing, persistent fatigue, and coughing up blood.
Regulatory Standards and Mitigation Efforts
Under UK law, mitigation measures must be implemented in workplaces where radon levels exceed 300 becquerels per cubic metre (bq/m³), averaged annually. For sleeping areas such as prison cells, this threshold is lowered to 200 bq/m³, as per guidance from the UK health security agency. Despite these regulations, new documents disclosed under freedom of information laws reveal that high radon levels were measured at HMP Exeter as far back as 2020.
Specifically, radon levels on the D wing of the category B men's prison recorded a seasonally adjusted result of 2,750 bq/m³ in winter 2020 – over nine times the legal limit. A subsequent report by specialists CERAP UK in 2022 recommended suspending activities and occupancy in the affected areas. Further measurements from late 2024 into early 2025 show radon levels exceeding 900 bq/m³ in some parts of the prison, with one area detecting 1,235 bq/m³.
Specific Cases: HMP Exeter and HMP Lindholme
Approximately twenty to twenty-five current prisoners at HMP Exeter have contacted law firm Kesar & Co, which is leading the HMP Dartmoor legal action, regarding their potential exposure to harmful radon levels. A similar number have approached the firm about exposure at HMP Lindholme near Doncaster. Inaam Barkatoolah, solicitor at Kesar & Co, stated: "The results for Exeter and Lindholme are very concerning. They show periods where radon levels have been extremely high in certain prison sections. Like the Dartmoor case, we have individuals suffering from radon poisoning symptoms – wheezing, fatigue, coughing up blood."
Freedom of information data indicates that testing at HMP Lindholme from 2019-2020 found excessive radon levels on the E wing. High levels were again measured across multiple wings in 2023, though these had reduced by 2025. Additionally, a separate site within HMP Lindholme's boundaries, along with sixteen probation sites across London, the South East, South West, Wales, the North West, East Midlands, and the East of England, have also recorded above-action radon levels.
Union Response and Ongoing Monitoring
The number of sites with high radon readings was uncovered in meeting notes recorded by the Prison Officers Association (POA) in early 2024. Mick Pimblett, deputy general secretary at the POA, commented: "Following concerns about radon control at HMP Dartmoor, the POA have been working with HMPPS to ensure radon levels are monitored by facilities management in all prisons in radon-affected areas. Where a prison is exposed to excessive levels, the POA are content that appropriate risk assessments are carried out and controls are in place."
A prison service spokesperson affirmed: "We take steps to actively mitigate the risk posed by radon in line with health and safety regulations and closely monitor the effectiveness of these mitigation measures." The Ministry of Justice confirmed that, of the thirty-three investigations prompted by the worrying radon levels, a small number remain awaiting final sign-off or under review.
A risk assessment for HMP Exeter conducted in May 2025 recommends banning prisoners from areas where radon concentrations exceed 300 bq/m³. This ongoing crisis highlights significant health and safety concerns within the UK prison system, with legal actions and continued monitoring underscoring the urgent need for effective radon management and transparency.
