Below you will find introductory information about radon gas and the risks associated with exposure:
Radon is a radioactive gas with no colour or smell. A material is radioactive when it emits particles or rays as it decays. Radon is produced by the natural decay of uranium, an element present in almost all types of soil, as well as in rock and water. In general, radon migrates upwards through the soil into the air we breathe. Although radon has always been present in the air, its concentration in homes has increased significantly in recent decades due to increasingly airtight construction designed to improve energy efficiency.
The concentration of radon gas in buildings is measured in Becquerels per cubic metre (Bq/m3). The maximum reference level for radon in workplaces and residential buildings in Spain is 300 Bq/m3, as specified in Royal Decree 1029/2022 of 20 December, following recommendations published by the Nuclear Safety Council (CSN) and the World Health Organization (WHO).
These recommendations, set out in CSN Safety Guide GS-11.02 “Control of exposure to natural radiation sources” and Instruction IS-33 on radiological criteria for protection against exposure to natural radiation (21 December 2011), constitute the basis for the regulations developed in Basic Health Document HS, Section HS 6 “Protection against exposure to radon” of the Technical Building Code (DB HS6), published in Royal Decree 732/2019 of 20 December.
According to DB HS6 of the Technical Building Code, before carrying out refurbishment or change-of-use works in existing buildings located in municipalities classified as Zone 1 or Zone 2 with respect to radon risk, a radon test must be carried out inside the building. If the radon concentration exceeds 300 Bq/m3, mitigation measures must be included in the project. The types of measures to be taken are detailed in DB HS6 of the Technical Building Code.
The radioactive atoms emitted by radon as it decays can attach to dust particles and become trapped in the lungs. As these atoms continue to decay inside the lungs, they release small bursts of energy that can damage lung tissue and may eventually cause cancer. According to the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), radon is the most significant source of radiation to which the general public is exposed, contributing around 43% of the total dose.
It is important to understand that reference levels should never be interpreted as a boundary between “no effects” and “effects”. The urgency and extent of corrective actions depend on how much the reference level has been exceeded.
To interpret radon levels in practical terms, data published by the WHO International Radon Project indicate that the risk of developing lung cancer increases by about 16% for every 100 Bq/m3 increase in radon concentration.
In many countries, radon is the second leading cause of lung cancer after smoking. The dose-response relationship is essentially linear, meaning that the risk of lung cancer increases in direct proportion to the increase in radon exposure.
Many researchers estimate that around 9% of lung cancer cases in Europe can be attributed to continuous exposure to radon gas. Only smoking is responsible for more lung cancer deaths. For this reason, radon reduction programmes in homes have been in place for more than 20 years in the United States and several European countries.
The likelihood of developing lung cancer due to radon depends mainly on:
If you smoke and are also exposed to elevated levels of radon, your probability of developing lung cancer is particularly high. The combination of smoking and radon exposure represents a very significant health risk. Stopping smoking and reducing radon levels in the air you breathe can substantially reduce this risk.
Certain types of radiation-induced cancer may affect children more than adults, but at present there is insufficient information to determine whether radon radiation poses a greater risk to children than to adults.
Radon can be found throughout Spain. It can infiltrate all types of buildings—homes, offices and schools—and gradually accumulate to high concentrations.
Not everyone exposed to high radon levels will develop lung cancer, and many years may elapse between exposure and onset of the disease. Nevertheless, exposure to radon represents a health risk, and measures should be taken to reduce that risk. Fortunately, effective solutions exist to prevent exposure and mitigate the dangers of radon.
Because radon is a gas present in air, it can enter a building and become trapped inside, reaching elevated concentrations. Radon moves upwards from the soil and enters the building through cracks and other openings in the foundations.
Radon can enter a home through:
Although soil radon is the main source in homes, in some situations the gas can also enter via well water. In a small proportion of buildings, certain construction materials can also emit radon. In Spain, however, it is estimated that around 80% of indoor radon comes from the subsoil and only about 20% from the nature of the construction materials.
Any building can have radon problems—whether new or old, well sealed or draughty, with or without a basement.
Radon concentration in air is measured in Becquerels per cubic metre (Bq/m3). A certain level of radon is normal; in Spain, average indoor levels are around 40–50 Bq/m3.
Maximum recommended indoor radon levels in Spain for residential buildings are specified by the Nuclear Safety Council (CSN) and follow WHO recommendations. Reference levels are used to assess the need for corrective actions to reduce radon concentrations. For existing buildings, a reference level of 300 Bq/m3 is recommended, while for newly constructed residential buildings the design objective should be 100 Bq/m3.
The level of 300 Bq/m3 should not be understood as the boundary between “safe” and “unsafe” levels, but rather as an “action level”. The lower the radon concentration in your home, the better for your own health and that of your family.
The higher the radon level, the greater the risk of lung cancer. Recent studies show that the risk increases by approximately 16% for every 100 Bq/m3. By reducing radon levels in your home, you can lower your risk of developing lung cancer. In most homes, radon can nowadays be reduced fairly easily to 75 Bq/m3 or less.
Yes. The Nuclear Safety Council (CSN) establishes in its publication GS-11.01 “Guidelines on the competence of laboratories and radon measurement services in air” that radon measurement services in air must use an analysis laboratory accredited according to the international standard ISO/IEC 17025 “General requirements for the competence of testing and calibration laboratories”. Radiansa follows the protocols established by the CSN and works with an ISO/IEC 17025-accredited laboratory.
No. Radon levels cannot be measured directly with a Geiger counter. A Geiger counter measures the ambient gamma dose rate; a high dose rate may indicate a high concentration of uranium in the subsoil, suggesting an area with a greater probability of elevated radon levels in buildings. However, a specific radon detector is required to determine whether indoor radon concentrations exceed recommended values.
Radon gas:
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