The Ministry of Justice is investigating 42 prison and probation sites for unsafe levels of radon gas, a figure that has risen from 33 sites, according to the ministry. HMP Dartmoor in Devon was closed in 2024 after radon levels 10 times higher than the recommended limit were recorded in one area, the ministry reported. Legal action is being led by law firm Kesar & Co on behalf of former prisoners and staff over radon exposure at HMP Dartmoor, the firm said.
The firm has instructions from people who believe they were affected by radon at six prisons: HMP Exeter, Channings Wood, Lindholme, Portland, The Verne, and Dartmoor, Kesar & Co stated. High radon levels were measured at HMP Exeter in 2020, with parts of D wing over nine times the legal limit, yet the prison remains fully operational despite these risks, according to measurements. The financial and operational consequences are significant, with the government spending around £4 million a year on the empty HMP Dartmoor because it is locked into a lease signed after high radon levels were discovered, government sources said.
Mitigation measures must be implemented in workplaces if radon levels exceed 300 bq/m³ annually, and in sleeping areas like prison cells if they exceed 200 bq/m³, according to regulatory guidelines. Dartmoor has been evacuated due to radon, but other sites with potential risks have not been evacuated, officials noted. Radon is a colorless, odorless radioactive natural gas that increases the risk of lung cancer, with over 1,100 deaths attributed to it annually in the UK, health experts report.
It remains unknown how many inmates and staff have been exposed to unsafe radon levels across the 42 sites, what specific mitigation measures have been implemented beyond HMP Dartmoor, and the timeline for addressing risks at the remaining 41 sites.