Radon exposure: health risks, lung cancer and what to do in UK homes

Radon is a naturally occurring radioactive gas. UKHSA explains that it is formed by the radioactive decay of small amounts of uranium found in all rocks and soils. Outdoors it is diluted to very low levels in the air we breathe. Indoors, the HSE says, levels can be higher, because the gas can enter and accumulate in buildings.

UKHSA notes that for most people radon is the single largest source of radiation exposure, whether at home or at work. UKradon states that every building has some radon and that in most areas the levels are low, while some buildings in radon Affected Areas have higher levels.

Radon exposure is not a disease in itself. It is a hazard, and it matters because of what it can do to the lungs over many years.

UKradon explains the mechanism simply. Radon produces a radioactive dust in the air we breathe. The dust is trapped in the airways and emits radiation that damages the inside of the lungs. This damage, like the damage caused by smoking, increases the risk of lung cancer. The higher the radon and the longer the exposure, the greater the risk.

The sources describe no short-term illness. UKradon says it is mainly the lungs that are exposed to and damaged by radon, and that there is no consistent evidence that radon causes cancers elsewhere, or other harm. Exposure is therefore a long-term, silent risk, which is why the sources emphasise measurement rather than symptoms.

UKradon cites a European study funded by Cancer Research UK and the European Commission showing that radon in the home increases lung cancer risk, and an independent report, Radon and Public Health, estimating that radon is a cause in over 1,100 lung cancer deaths each year in the UK.

UKradon publishes estimates of lifetime risk of lung cancer due to radon, which depend on the indoor radon level (measured in becquerels per cubic metre, Bq/m3) and on smoking history. The table below reproduces these estimates and shows why the page tells smokers to give up.

Even at a low level of 20 Bq/m3 the risk for a current smoker is 1 in 7, compared with less than 1 in 200 for a non-smoker. The effect of smoking and radon together is far greater than either alone.

The HSE says excessive levels of radon can occur in almost any type of workplace, and that the amount that collects in a building depends on its location, structure and how it is used. Underground workplaces such as basements, cellars, mines, caves and utility service ducts can have significant levels, as can above-ground workplaces mainly in affected areas. Employers occupying only parts of buildings from the first floor and above are less likely to have significant radon than those on the ground floor or below.

UKHSA has published maps of radon Affected Areas, created by combining measurements in houses with maps of the underlying geology. UKradon says buildings in these areas should be tested. Under UK regulations the HSE states that all employers must review the potential radon hazard in their premises, and workplaces in affected areas should be tested unless a detailed assessment shows good reason to expect low levels. The HSE adds that the Ionising Radiations Regulations 2017 apply where radon is present above 300 Bq/m3 as an annual average.

UKradon describes three steps. First, check whether your property is in a radon Affected Area. Second, if it is, order a radon measurement pack for the home or workplace, which gives the yearly average level and shows whether it is above or below the Action Level. Third, if the level is high, reduce it with simple building works.

The HSE says measurement is simple and cheap, using small plastic passive detectors left in rooms and returned by post to a validated laboratory, and that high levels are relatively easy to address, for example with a sump.

Buyers and sellers, landlords and employers all have a role. UKradon has separate information for householders, employers, professionals such as solicitors and builders, and for local authorities and housing associations.

• Check whether your postcode is in a radon Affected Area.

• If it is, measure over a long period with a validated detector.

• If the result is high, arrange building works to reduce it.

• If you smoke, giving up is the single most effective step for your lungs.

The sources do not describe any symptom that is specific to radon, and the HSE notes that you need special equipment to detect it, so the only way to know a building's level is to measure it. The medical concern is lung cancer, and any new or persistent chest or breathing symptom should be taken to a GP whatever the radon level. Sudden severe breathlessness or chest pain needs urgent help through 999 or A&E.

If you have lived or worked for years somewhere with a high measured radon level, tell your GP, particularly if you smoke or have respiratory symptoms, so that any symptoms are taken seriously.

Radon is dealt with through building measurement and remediation rather than through health services. The health service role is the usual one for lung health: assessing symptoms and investigating suspected lung cancer, with UKradon advising that smokers give up.

Measurement is arranged through UKHSA's UKradon service or other validated laboratories, and remediation through building contractors. Because the evidence is in the table above, the practical priorities are simple: measure if you are in an affected area, reduce high levels, and do not smoke.