Mapping of soil radon potential areas in the department of Maine-et-Loire(49)

Radon is a naturally odourless, colourless and chemically inert radioactive gas. It is derived from the decay of uranium and radium present in soil and rocks.

Radon is present everywhere: in air, soil, water with a very variable concentration from place to place, according to many factors: pressure, temperature, porosity, ventilation
In outdoor air, radon dilutes rapidly and its average concentration generally remains very low. On the other hand, in enclosed spaces such as buildings, it can accumulate and sometimes reach high concentrations.

The areas most affected by high levels of radon in buildings are those with naturally uranium-rich geological formations (granite and volcanic subsoils).
Mapping of areas where radon is most likely to occur at high concentrations in buildings is based on the mapping of radon potential of geological formations by the Institute for Radioprotection and Nuclear Safety (IRSN).
This mapping led to the classification of municipalities into 3 categories:
*Category 1: Category 1 radon-potential municipalities are those located on geological formations with the lowest uranium content. On these formations, the vast majority of buildings have low radon concentrations.
*Category 2: Category 2 radon-potential municipalities are those located on geological formations with low uranium content but where particular geological factors may facilitate the transfer of radon to buildings. These particular geological conditions can locally facilitate the transport of radon from the rock to the soil surface and thus increase the likelihood of high concentrations in buildings.
*Category 3: Category 3 radon-potential municipalities are those with at least part of their area with geological formations with an estimated higher uranium content compared to other formations. Of these uranium-rich formations, the proportion of buildings with high radon concentrations is higher than in the rest of the territory.