Radon is a radioactive, colourless, odourless, inert, and tasteless gas produced by the natural radioactive decay of uranium, which is present in most soils and rocks.
This gas enters buildings through cracks, pipes, ducts, or pores in the ground and tends to concentrate in the interiors of buildings such as homes, schools, and workplaces, especially in basements, cellars, or in the parts most in contact with the ground. It adheres to dust particles in the air and is, therefore, a potential health hazard. Moreover, as the gas dissolves in water, dwellings supplied by a well may have an additional risk factor.
Some materials, such as granite, slate, or phosphate plasters, are more permeable and allow greater amounts of radon to be emitted from the ground. At the other extreme, impermeable soils, such as clay, make it more difficult for the chemical element to reach the surface.
However, living in a geological area with high radon levels does not necessarily mean that your home has high radon radiation, the only way to know this is to take a measurement.
Although radon gas itself does not make the house uninhabitable, high concentrations of radon in the house can pose a serious health risk to its inhabitants. It should be noted that it is harmless in open spaces and only harmful in enclosed spaces and above certain limits and that the concentration also depends on practices and habits that may favour its accumulation, such as poor ventilation or very airtight construction.
Although most homes do not have radon levels above the limits set in several countries, there are still a worrying number of homes with elevated radon levels.
To make a house with elevated values safe again, it is necessary to take measures to reduce the radon content. This may include the adjustment or installation of ventilation systems, sealing measures to prevent radon infiltration and other remediation/mitigation methods.
Testing is usually carried out in the basement of buildings, and in some places, such as many states in the United States, radon gas measurements are required before a house can be sold because of the hazardous nature of radon.
When the radon radiation level in a home is to be determined, it should be done in three special situations: during the winter months, early in the morning and in places that have been closed during the night. Otherwise, the detected values will have a relative value.
Although figures on the effects of radon are still highly debatable, the maximum exposure limit recommended by the US Environmental Protection Agency is four picocuries per litre of air. Prolonged exposure to this dose is estimated to have a health risk comparable to smoking half a packet of cigarettes a day or having 200 X-rays a year.
A particularly striking case in the history of radon occurred in 1984 when an American engineer, Stanley Watras, working at a nuclear power plant in Limerick (Pennsylvania, USA) detected that the amount accumulated in his home was 16 times higher than the maximum limit tolerated in uranium mines. This level of radioactivity posed a health risk similar to smoking 135 packs of cigarettes a day.
When you want to know the level of radon radiation in a home, you have to do it in three special situations: during the winter months, early in the morning and in places that have been closed overnight. Otherwise, the detected values will have a relative value.
Is it really that dangerous?
Radon is a noble gas whose radioactive isotope Rn-222 is commonly known as radon. Due to the radioactive properties of Rn-222, it emits alpha radiation during its radioactive decay which is ionising radiation that can affect the DNA of our cells. Other types of ionising radiation are beta and gamma radiation. However, alpha particles have a high atomic mass, which means that they can emit much more energy per unit length. This energy release is significantly higher than that of beta or gamma radiation. Therefore, the damage that alpha radiation causes to our DNA is much greater.
Radon is a noble gas. This means that it cannot form chemical compounds with other elements. So where is the danger of radon gas? The answer lies in what are called ‘radon progeny’. These are not gases, but radioisotopes that can attach to the respiratory tissues of the lungs. Some of the radon progeny (Po-218 and Po-214) emit alpha radiation with high energies that can damage lung tissue.
Reasons for measuring radon
The problem is that, as we breathe, the particles are deposited in the cells lining the airways, where they can damage DNA and cause lung cancer. According to the International Agency for Research on Cancer (IARC), this gas is classified as a Group 1 carcinogen. For the Spanish Association Against Cancer (AECC), the effects are synergistic, i.e. smoking and living in a house with a high radon content increases the risk of cancer ‘some 46 times more than if the two phenomena were to occur separately’, but it is estimated that ‘more than 10% of radon-related cancer deaths occur among non-smokers’.
Worldwide, some 230,000 people suffer from lung cancer caused by radon (about 1,500 in Spain), yet the health risks associated with long-term exposure to high levels of radon are relatively poorly understood.
In Spain, RD 1029/2022 regulating exposure to radon in workplaces has been in force since 2022, and the national radon plan was approved in Spain in January 2024.
Where is it located?
Although all buildings may contain low concentrations of radon, there are some geographical areas which, due to their geology, are likely to contain higher levels. The map of radon potential in Spain, developed by the Nuclear Safety Council (CSN), categorises these areas according to their levels and, in particular, establishes those with concentrations above 300 Bq/m3 .
According to this map, 90% of the buildings have concentrations below this amount and 10% exceed it. Special care should be taken in areas such as Galicia and Extremadura, where the risk is higher. Contrary to what might be assumed, the areas with the most radioactivity are not close to nuclear power plants. This is because the culprit is precisely radon gas.
