The definition of radon according to the Centres for Disease Control and Prevention is “an odourless and invisible radioactive gas naturally released from rocks, soil and water. Radon can get into homes and buildings through small cracks or holes and build up in the air. Over time, breathing high levels of radon can cause lung cancer” (1). Radon originates from uranium decay, which emanates from the soil, dilutes in the atmosphere and remains there in relatively low concentrations (2).

However, radon builds up in closed spaces such as dwellings or workplaces, sometimes reaching indoor concentrations above the World Health Organisation or European Union reference levels (2). Radon is found in groundwater, rocks and soil; it can seep into the house through construction joints, cavities and cracks inside walls, cracks in sump pumps, cracks in floors, gaps around service pipes, gaps in suspended floors, in private wells and underground water supplies. High radon levels in the water supply are more likely when its source is groundwater, such as a private well or a public water supply system that uses ground water. Most public water supplies come from surface water (lakes, rivers and reservoirs) (3).

Radon is one of the leading causes of human lung cancer. When you breathe in this gas, radioactive particles can get trapped in your lungs and over time, these radioactive particles increase the risk for lung cancer (1). Radon was first revealed to cause lung cancer in uranium miners exposed to high concentrations of this gas. Consequently, epidemiological studies were conducted in Europe, North America and China to observe the relationship between the exposure to radon inside the homes and the risk for lung cancer. Results from these studies confirmed that exposure to radon in dwellings can be considered a risk factor for developing lung cancer (4).

Actions you can take to reduce radon levels throughout the home include (1) (4):

  • Open Windows, use fans and ventilators to circulate air.
  • Seal cracks in floors and walls with plaster and/or materials designed for this purpose.
  • When buying a new house, ask about radon-resistant construction techniques.
  • Stop smoking.
  • Prevent radon from leaking from the basement into the rooms.
  • • Install a mechanical radon evacuation system in the basement or under solid floors.

The Spanish National Radon Potential Map establishes this toxic substance’s prone areas, where 10% or more of the dwellings present radon levels above 300 Becquerels per cubic metre of air (Bq/m3) at basement or ground floor. In Spain, 17% of the territory is classified as radon prone, with large variations amongst regions. Since 2019, the Spanish Building Code has enacted mandatory radon protection measures for new buildings and rehabilitation, based on a list of radon prone municipalities (2)(5).


  1. CDCespanol. Centers for Disease Control and Prevention. 2023 [cited 20 October 2023]. Radón en la casa. Available at:
  2. Martin-Gisbert L, Candal-Pedreira C, García-Talavera San Miguel M, Pérez-Ríos M, Barros-Dios J, Varela-Lema L, et al. Radon exposure and its influencing factors across 3,140 workplaces in Spain. Environ Res. 16 October de 2023;117305.
  3. CDC. Centers for Disease Control and Prevention. 2021 [cited 20 October 2023]. Radon in the Home. Available at:
  4. El radón y sus efectos en la salud [Internet]. [cited 20 October 2023]. Available at:
  5. Mapa del potencial de radón en España – CSN [Internet]. [cited 20 October 2023]. Available at:


Mónica Miriam García Cuéllar
Master’s Degree in Public Health and Health Promotion
OSMAN Scientific Editor