BBC report reveals high radon levels at Dartmoor Prison were known 13 years earlier than government claimed

High levels of radon gas were detected at Dartmoor Prison more than a decade before the government previously acknowledged, according to a BBC investigation.

The Ministry of Justice (MoJ) had stated that “elevated radon readings were first found at Dartmoor in 2020,” when the prison was later closed in August 2024 after radiation levels up to 10 times higher than the recommended safety limit were recorded in some areas.

However, the BBC has obtained an official letter dated September 2007 showing that radon monitoring had already taken place at the site 13 years earlier, and that some readings were found to “exceed the threshold at which the regulations apply”.

According to the BBC’s report, the letter, sent from the Health Protection Agency to the prison’s works department, stated:

“Please find enclosed the Report of Radon Measurements, which gives the results of the radon gas measurements taken with passive monitors. One or more of the enclosed results exceed the threshold at which the Regulations apply.”

The MoJ has since confirmed that monitoring took place in 2007 and that ventilation improvements were made in response.

The revelation has raised questions about whether His Majesty’s Prison and Probation Service (HMPPS) acted quickly enough to protect staff and inmates from long-term exposure to the radioactive gas.

Solicitor Mladen Kesar, who represents more than 500 claimants, including former prisoners, officers, and staff, said hundreds more could have been exposed if high readings were known in 2007.

“So many people went to work, not knowing that they were risking so much,” he said.
“But the authorities knew.”

Radon is a colourless, odourless radioactive gas produced by decaying uranium in rocks and soil, particularly granite. The UK Health Security Agency estimates that radon exposure causes about 1,100 lung cancer deaths each year.

A former Dartmoor prison officer, who is part of the legal action but asked to remain anonymous, told the BBC that the risks were well known inside the prison.

“Dartmoor Prison is built with granite. The walls are granite. Everything up there is granite,” he said.
“It’s always been renowned as being the worst job for retirement, because you don’t have much of a retirement, but there are so many staff that are dying through cancer.”

Although he has not been diagnosed with cancer himself, the former officer said he lives with ongoing concern about the potential impact.

“You cannot live waiting for that diagnosis. You’ve got to get on with it. However, you cannot stop fighting, because there’s a reason people are dying.”

When the prison closed in 2024, official monitoring had recorded radon levels of 2,988 becquerels per cubic metre (Bq/m³) in some areas - almost 10 times the UK workplace limit of 300 Bq/m³, set under the Ionising Radiations Regulations 2017.

The Health and Safety Executive (HSE) launched an investigation into the exposure in December 2023, which remains ongoing.

Sarah Rigby, the Prison Officers’ Association (POA) representative for the South West and South Wales, told the BBC:

“There is some anecdotal evidence that some of these radon issues go a lot further back than what was initially thought, or what was admitted to by HMPPS. That’s why we need the HSE investigation, really, just so we can sort of categorically know before we take any next steps.”

The HSE said: “This has been a highly sensitive, complex investigation under high scrutiny. The investigation is ongoing and we cannot comment further at this time.”

An MoJ spokesperson reiterated that monitoring and mitigation steps were taken in 2007, including ventilation improvements.

“Our priority remains the wellbeing and safety of our staff and prisoners,” the spokesperson said. “We are unable to comment further whilst the HSE investigation is ongoing.”