Fears hundreds more inmates exposed to cancer-causing gas in UK prisons
There are fears that hundreds of prisoners and staff have been exposed to unsafe levels of the cancer-causing gas, with the Ministry of Justice now inspecting 42 prisons and probation centres. Independent can reveal.
HMP Dartmoor in Devon was closed in 2024 after radon levels 10 times above the recommended limit were recorded at one site. The government currently spends around £4 million a year of taxpayers’ money on the empty prison because it is tied to a lease signed following the discovery of highly toxic gases.
At least 16 prisons have had “on-the-go” levels of the gas measured by authorities, including HMP Exeter, Lincoln, Lindholme and Channings Wood. Independent Last month, it was revealed that unsafe levels were recorded in 33 prisons and probation areas in 2024.
Now, in response to a freedom of information (FOI) request, HM Prison and Probation Service has admitted that this figure has risen to 42 facilities.
Radon is a colorless, odorless, radioactive natural gas that is formed as a result of the decay of small amounts of uranium in rocks and soil and can accumulate in closed areas. According to the UK Health Safety Agency (UKHSA), more than 1,100 deaths each year in the UK are attributed to radon, an increased risk of lung cancer.
Law firm Kesar and Co is leading a legal case brought by former prisoners and prison staff over potentially harmful exposures to radon at HMP Dartmoor. Lawyer Mladen Kesar said the firm had now received instructions from people who believed they were affected by radon in a total of six prisons; HMP Exeter, Channings Wood, Lindholme, Portland, Verne and Dartmoor.
Documents released under FOI laws show high levels of radon were measured at HMP Exeter in 2020, with parts of wing D exceeding nine times the legal limit. Further measurements from late 2024 to 2025 show levels in some parts of the prison were above 900 bq/m³.
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 UKHSA guidance, this amount is reduced to 200 bq/m³ for sleeping areas such as prison cells.
Mr Kesar said: “There is evidence of very high levels of radon in some areas in Exeter but the prison has not yet been evacuated. It is fully operational as if nothing was happening. Likewise in others. There is no sense of urgency or responsibility.”
“Dartmoor has been evacuated but people in 41 other counties are potentially at risk. If a deadly virus was discovered there you would think they would evacuate the prison and keep everyone safe, but somehow they are taking their time despite radon being the second biggest cause of lung cancer.”
Gemma Abbott, legal director at the Howard League for Sentencing Reform, said: “When the state detains people, it has a legal and moral obligation to ensure they are safe.
“Radon is known to increase the risk of lung cancer, and the Department of Justice has shown an alarming lack of urgency in addressing the risks, as well as failing to repair tens of thousands of prisons that fail to meet legal fire safety standards.
“Over the last seven months we have repeatedly requested copies of detailed risk assessments for prisons with radon values higher than permitted by law, but so far the government has refused to provide them.
“It must be terrible to be locked in an unsecured cell for up to 23 hours. What do ministers have to hide?”
A Ministry of Justice spokesman said: “We regularly monitor levels of naturally occurring radon gas on HMPPS land and take action to reduce risks where high levels are detected.”
