Radon is a naturally occurring radioactive gas produced by the decay of uranium and radium in rocks and soil. It is colourless, odourless, and tasteless — entirely undetectable without a test. Radon seeps from the ground into buildings through foundations, floors, and gaps. It is the second leading cause of lung cancer after tobacco smoking in the UK, responsible for approximately 1,100 lung cancer deaths per year. High-radon areas include granite-rich regions such as Devon, Cornwall, Derbyshire, and parts of Wales and Scotland.
Where it's found
Radon enters buildings from the underlying soil and rock through cracks in foundations, hollow block walls, gaps around service pipes, and through porous concrete. Concentration varies enormously between buildings even in the same street. Ground floor and basement rooms have the highest concentrations. Radon also dissolves in groundwater — private well water in high-radon areas can release radon into indoor air when used for showering and cooking. Building materials derived from natural rock (granite worktops, stone floors, some bricks and tiles) can contribute a minor additional source.
Routes of exposure
Inhalation is the primary route of health significance. Radon gas itself is relatively harmless; the danger comes from its short-lived radioactive decay products (polonium-218 and polonium-214) which attach to airborne particles and can be inhaled and deposited in the lung, where they emit alpha radiation directly to bronchial tissue. Ingestion via well water is a secondary pathway. Radon concentrations in buildings fluctuate with weather, season, building ventilation, and occupant behaviour — concentrations rise in winter when buildings are closed up.
Health concerns
Radon exposure is a confirmed human lung carcinogen — IARC Group 1. Alpha radiation from radon decay products damages DNA in bronchial epithelial cells, causing mutations that drive lung cancer development. The lung cancer risk from radon is strongly multiplicative with tobacco smoking — a smoker in a high-radon building has a significantly higher risk than either factor alone. WHO estimates radon causes between 3% and 14% of all lung cancers worldwide. Radon is the dominant environmental cause of lung cancer in non-smokers. There is also emerging evidence of association with leukaemia and other cancers.
Evidence
IARC Group 1 classification is based on direct evidence from underground miners exposed to high radon concentrations, supported by residential epidemiological studies at lower concentrations. Pooled analyses of European and North American residential studies demonstrate a statistically significant dose-response relationship down to 100 Bq/m³ — near the reference level in many countries. The biological mechanism (alpha radiation causing DNA damage) is unambiguous. UK Health Security Agency and WHO provide clear public health guidance.
Who's most at risk
Smokers in high-radon homes face dramatically elevated lung cancer risk due to synergistic interaction between radon and tobacco carcinogens. People spending the majority of their time in lower floors of high-radon buildings have the greatest cumulative exposure. Residents of Devon, Cornwall, Derbyshire, Northamptonshire, Lincolnshire, and parts of Wales and Scotland live in higher-radon areas. Those in poorly ventilated older properties without underfloor ventilation have higher indoor concentrations. Children may be at greater radiological risk due to smaller lung size and faster breathing rate.
Regulatory status
RegulationUK Building Regulations require radon-protective measures in new buildings in designated high-radon areas. The UK reference level is 200 Bq/m³ for existing homes and 100 Bq/m³ for new builds and workplaces. UKHSA recommends action to reduce radon above 200 Bq/m³. The Workplace Exposure Limit is 300 Bq/m³. EU Council Recommendation 90/143 set a reference level of 400 Bq/m³, now tightened under EU BSS Directive 2013/59 to 300 Bq/m³ for homes.
How to reduce your exposure
Test your home for radon with a long-term passive radon detector — these are inexpensive (around £30–50) and available directly from UKHSA or approved suppliers. Testing for 3 months gives a reliable seasonal average. If results are above 200 Bq/m³, radon reduction measures are straightforward and effective: positive input ventilation (PIV) systems, radon sumps beneath the ground floor, sealing gaps in floors and around service pipes. Improving general ventilation and keeping windows open when weather allows reduces indoor concentrations. UK Radon Association provides a postcode-level risk assessment tool.
The nutrition connection
Radon is entirely invisible and odourless, so awareness and testing are the only tools — there is no dietary intervention that affects radon risk. However, Nutriofia's perspective is relevant here in a different way: the single most powerful modifiable factor in radon-related lung cancer risk is smoking. The synergistic interaction between radon and tobacco means that stopping smoking dramatically reduces the risk from any given radon concentration. For people in high-radon areas who smoke, smoking cessation and radon remediation together represent the two most impactful actions possible for reducing lung cancer risk — and supporting nutritional strategies for lung health (antioxidants, anti-inflammatory dietary patterns) complements both.