The most radioactive parts of the UK

The average radioactive background dose in the UK is 2.7 millisieverts. Of this 2.7 mSv, 1.35 mSv comes from radioactive radon gas leaking out of the ground.

This radioactive radon (Rn-222) is produced by the decay of uranium-238, after a series of intermediate non-gas stages that cannot escape from rocks.

Because radon has such a large effect on the annual radiation dose that someone receives, it is closely monitored. In the UK, this monitoring is done by the Health Protection Agency (HPA). One of the things that the HPA does it produce radon maps, showing which areas of the UK have the highest presence of radon.

The map is graded by the percentage of homes in that area which have a level of radon beyond the action level of 200 becquerels per cubic metre (200 radon decays per second per cubic metre).

There are a number of important radon hotspots in the UK. The most noticeable one is Cornwall in the south-west where the average UK background dose is 7.8 mSv, nearly three times the national average. This is due to the presence of igneous granite, which naturally contains more uranium (10-20 parts per million) than other rocks.

Radioactive areas tend to be hilly, where igneous rocks have been forced to the surface or left behind by the erosion of softer sedimentary rocks (the Chiltern Hills are particularly radioactive, for example). The Yorkshire Dales sit on top of an underground deposit of pink granite called the Wensleydale Granite that lies underneath the Askrigg Block, and the Peak District features many granite outcroppings.

47 thoughts on “The most radioactive parts of the UK

  1. Hi

    You said that the Chiltern Hills are par­tic­u­larly radio­active. I’d be interested to know more about this as the Chilterns aren’t that far from me. Do you know if there are exposed areas containing uranium and/or thorium in the Chilterns? If so, can you say where exactly?



  2. Steve,

    The level of radioactivity is extremely low, and you have absolutely nothing to be concerned about. If you’re interested, you can find a map of radon levels here.

  3. Thanks but I’m not worried about radiation – I get exposed to plenty of that! I collect radioactive minerals, that’s why I was interested. I’d be absolutely delighted if it was possible to find them in the Chilterns! Is there any chance of finding anything interesting there near the surface?



  4. I live in a first floor flat 1 level up from ground surely there is a low risk being well away from ground .I live in Camborne cornwall on the edge of town. I have been offered radon detectors by my local authority

  5. Yes. The closer to the ground you are, the more problematic radon is likely to be (basements are the really problematic areas), but being on the first floor doesn’t mean you’re necessarily safe. Just use the radon detectors to find out if it’s problematic where you are living.

  6. Please can you tell me if Torpoint Cornwall is a low radon area

  7. Mr Reid, do radioactive rocks increase the temperature of the rock/ground? If so is this sufficient to cause any changes such as weather changes or heating up lakes?
    I try to answer questions put to me by Junior school children but this had me stumped. I need a basic answer for 10yr old. He asked after we discussed Global Awareness Day and topics such as climate change and social consequences. Thanks. Mrs Lodder. Yr6

  8. Close to the surface, no. But deeper down? Absolutely. That’s where Earth’s internal heat comes from. Geothermal power is just nuclear power, one step removed.

  9. Your article mentions the UK in the title but only has data and a map relating to England and Wales, thus excluding over one third of the UK. Oops.

  10. hi my husband worked as a piller foundation engeneer all over britain and mainly in the west country drilling the ground so many meters to test the structure is this area a high risk area for uranium and any other radiation i really need to know asap many thanks

  11. Hi Mr Reid, we are looking into moving to the south-west from the south-east but the presence of Radon is something that it making us think twice. Is there any health risk related to living in a general area with a higher background level? Is there a quick and easy way of assessing levels in individual houses when viewing rather than waiting for a survey by which time we would have invested time and money? I’ve looked into buying a Geiger counter but would this give us any useful information during a 15 minute viewing? Thanks for your help!

  12. The main risk of excess radon is an increased risk of lung cancer, but evidence suggests that increased radon levels in Cornwall are not reflected in a higher incidence of lung cancer (though I haven’t researched this in much detail). I don’t know a good way to measure the radon levels in a home in a short period of time (most radon surveys last three months or longer), but it is feasible to carry out remedial work if excess radon is found to be present. You should definitely ask sellers about any radon remediation work if the house you want to buy is in an affected area, especially if it was built pre-1988.

  13. Thanks very much for the advice. Would a Geiger counter tell us anything at all comparing relative radiation levels in our Essex home to a home in Devon whilst viewing or would this be a complete waste of time?

  14. There will be blips here and there, but generally Brighton is not in a particularly high radon area when compared with the South West.

  15. hi
    I,m writing an important SA for a physics competition. and I was wondering, as I live in cornwall, wether you perhaps knew if solar rays can be absorbed by granite rock?.

  16. It’s “essay”, not “SA”.

    It depends on what you mean by “solar rays”. If you’re talking about light and heat from the Sun, then that can be absorbed by anything it hits.

  17. Hi Mr. Reid,

    Do you have sources for the average background dose and percentages from different paths?

  18. Well it depends on what that 0.3% is of. “0.3%” is a meaningless figure without context.

    If 0.3% of the air is radon, then yes, that’s a pretty big problem. If the level of radon is 0.3% of the action level, that’s not a problem at all.

  19. There’s a possibility in scientific hypothesis that low doses trigger the biological system into resistance. Its not proven yet but the science is building fast in recent years. Obviously there’s an enormous vested interest in science itself resisting this possibility – large wealth and many careers stand on it being untrue. It might explain why low radon doses have had no effect in Cornwall and indeed for it to be a mistake of ignorance to do remediation. Even very low doses are less of a trigger it claims. Of course, high doses are lethal but these do not appear in general for radon in Cornwall. Nevertheless, radon in Cornwall seems to fit the hypothesis but its not been analysed properly yet there. The idea is known as ‘radiation hormesis’. Google it, there’s plenty of scientific papers on it.

  20. Robin Smith, possibly more than theoretical. One of the eminent physics professors was said to be looking into this before his retirement. He was apparently looking at Iran where the levels of background radiation are very high, 132 mSv/yr. There was said to be some evidence that radiation damage to human tissue in that area is repaired by the body but the story at this stage is anecdotal.

  21. Your map of the UK is significantly deficient! The part you show does not have a name! It has two names, England and Wales

    The granite in Scotland would be an interesting subject as would the waters round Dounreay and Loch Long where the nuclear subs are kept.

  22. You seem to have missed out a third of the British landscape Mr Reid
    Where is Scotland?

  23. You replied to an earlier comment that data was not available for Scotland at the time you compiled your graphics.

    Firstly, where did you enquire for that information, please?

    And secondly, the title of your article is therefore erroneous, since you appear to be conflating the UK with England and Wales.

  24. You talk about radioactivity in the UK, but no mention of Scotland? Last I heard we were still part of the UK.

  25. No data for Scotland is available. Therefore I am covering the whole UK, it’s just that there is no Scotland data.

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  27. Mr Reid, radon has come up on our searches for a house we want to buy. We are near the Chilterns in a 1-3% area. We have so many questions:
    Does the health risk warrant moving away?
    Why is outdoor radon not mentioned anywhere? Is it not a risk?
    What about schools and other public buildings?
    If risks are small why are searches like that carried out?

    Would be grateful for any advice.

    Thank you.

  28. No. Houses can be treated to prevent radon from seeping in. The house you want to buy may already have been. Outdoor radon doesn’t accumulate. Those buildings will have been treated. The risk is small, if mitigated. Searches are carried out so that areas where mitigation is required can be identified.

  29. I see from your map, the Lizard peninsular has a lower radiation level than the rest of Cornwall. Is this a direct result of the exceptional accession above the European continental plate in this area? Has the this area a lower geological risk of higher than normal national levels, caused by Radon gas?

  30. It’s to do with the geology of Cornwall. The Lizard Complex doesn’t have the same geology as most of the rest of Cornwall, in particular it is missing the granite that is responsible for most radon emission.

  31. I live near Dartmoor in Devon and grew up in Cornwall so know the SW very well. Just for fun I’m about to survey some old mine entrances on Dartmoor to try and quantity the increased radon levels that may be present – using various instruments (alpha GM / gamma scintillation coupled to an old Ludlum model 16) – I’m a geophysicist by profession but this is just for fun and something to do while taking the dog for a walk.

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