Radon (Rn) is a naturally occurring inert and radioactive gas. It is produced from the radioactive decay of radium, as part of the decay chain of uranium. Its most stable isotope, radon-222, decays within a few days, emitting ionizing radiations in the form of alpha particles and transforming into its decay products, or “progeny”, including polonium-218 and polonium-214, which also emit alpha radiation. Radon is odourless, colourless and tasteless, and cannot therefore be perceived by our senses. If inhaled, it is very dangerous to human health because the alpha particles can damage the DNA of cells and cause lung cancer.
The radioactivity of radon is measured in Becquerels (Bq), where one Becquerel corresponds to the transformation of one atomic nucleus per second. Concentration in the air is expressed in Bq/cubic metre, which is the number of transformations per second in a cubic metre of air.
The main health hazard from radon exposure (and the only health hazard currently supported by epidemiological evidence) is a statistically significant increase in the risk of lung cancer. Globally, radon is considered to be the most dangerous source of radioactive contamination in enclosed environments, and accounts for about 50% of average human exposure to ionizing radiation.
The decay products of radon pose a greater threat to human health than radon itself: being electrically charged, they attach themselves to particulate matter in the air and enter the body through the airways. When this “progeny” sticks to the surface of lung tissue, it continues to decay and emit alpha particles that can directly or indirectly damage the DNA of cells. The damage, if not properly corrected by the cell repair mechanisms, can ultimately lead to cancer formation.