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Important change to radon data in our reports and data packs

Important change to radon data in our reports and data packs

There have been some significant changes to the radon dataset developed by the British Geological Survey (BGS) in conjunction with the UK Health Security Agency (UKHSA – formerly known as Public Health England). The map of potential radon gas exposure has been redrawn across England, Wales and Scotland, including a general uprating in areas formally less known to have radon naturally occurring.

These could impact a client’s view on their existing property and land transaction and give conveyancers, commercial real estate lawyers and environmental consultants pause for thought about any possible implications. 

Updates reveal new radon-affected areas

From today, a new BGS Radon Potential Dataset has been released which reveals that whole new parts of the country, including Southeast England, the Midlands (in particular around the Coventry area) and South Wales at an elevated level of exposure to radon gas. 

The original dataset was built on some 479,000 sampling tests and identified higher levels that could affect properties in the Southwest and Northwest of England and Wales. But now new research has revealed the potential affected areas to be far more widespread. 

The updated dataset now combines 560,740 indoor radon measurements provided by the UKHSA, with updated geology provided by the BGS and has shown a significant increase both the number of sites and also the distribution, as you can see from the maps. 

Map showing the changes to ratings to radon potential in the Brighton and Hove area. 

Before and after changes across the South East of England showing elevated levels across the Downland and Greensand Ridge. 

While the ratings for potential emission haven’t changed, accuracy and location data has been improved. There is a strong link to geology, following the folds of the Downs in the southeast of England for example. 

What is Radon? 

Radon is an invisible, odourless and naturally occurring radioactive gas released through the decay of uranium, which is present to some degree in all soils and rock.  It causes more than 1,100 deaths from lung cancer each year* in the UK and is responsible for more premature deaths than drink-driving and workplace accidents combined.

Certain types of rock, such as granite are more prone to releasing the gas through cracks and faults.  It can be drawn in by warm air inside a house via suspended floors or gaps and cracks in a building’s structure, such as service pipes.

How is Radon measured? 

The measurement for Radon is becquerels per cubic metre of air (Bq m-3). The average reading for radon levels in most of the homes is around 20 Bq m-3.

UKHSA has set the UK Action Level for radon at 200 Bq m-3. Anything above this needs further action to reduce radon levels in the property.

The national risk measurement is divided as follows:

  • Less than 1% of properties are above the action level (level 1)
  • Between 1% and 3% of property are above the action level (level 2)
  • Between 3% and 5% of property are above the action level (level 3)
  • Between 5% and 10% of property are above the action level (level 4)
  • Between 10% and 30% of property are above the action level (level 5)
  • Between 30% and 100% of property are above the action level (level 6)

What does this mean for the transaction?

Although invisible, radon levels are easily measurable and can be reduced by undertaking testing and making modifications to your client’s property. However, this is not a quick process and if the property does not have any existing modifications and is in a higher risk area, testing and remediation can take several months and could significantly slow down the transaction.

Since the 1990’s all new build properties should have had radon precautions installed. This could be a plastic membrane, a sump or air bricks. Planning conditions for extensions in affected areas usually require protective measures to be installed that could be basic or full depending on the % of dwellings exceeding the Radon Action Level. Older properties can be retrofitted with radon protection measures and there is no restriction if the property is in a conservation area or has listed status.

How should I advise my client with these changes? 

We recommend that for any ongoing conveyancing transactions or development projects, you may wish to discuss this with your client and consider getting a refresh Radon Check or obtain a new environmental search through your search provider. Conveyancers, please note that your client’s CON29 local authority search result may also differ after the 1st December. 

If you have any more questions about radon and how it could affect your client’s transaction, email us at or call us on 01273 257 755. 

*1100 deaths per year figure comes from University of Oxford research funded by Cancer Research UK, the Medical Research Council, the European Commission sixth framework programme, and the National Institute for Health Research. The study was published in the peer-reviewed British Medical Journal.


Dec 1, 2022

David Kempster