A new study has shown that radon gas, generated by the decay of uranium, is the second leading cause of lung cancer after smoking.
The odourless and tasteless gas is generated by decay of uranium-238 (a natural radioactive element present in all rocks and soil in varying degrees).
The radon gas is emitted by the subsoil and seeps into houses - to a greater or lesser degree depending upon the permeability of the ground - through the pores and cracks in garages and basements.
The researchers from the University of Cantabria and the Romanian Babes-Bolyai University studied the exposure to this element in a uranium mining area in Transylvania and in an area of granite in Torrelodones, Madrid.
The authors estimated the death rate due to lung cancer attributable to radon and smoking in the areas between 1994 and 2006.
The result was double that which would have been expected based on a relative risk report produced in 2006 for the whole of Europe on cancer incidence and mortality.
"The study shows that radon is the second leading cause of lung cancer, after smoking, as has also been shown by many other studies carried out over the years in various parts of the world", Carlos Sainz, co-author of the study and a researcher for the Ionizing Radiation Group at the University of Cantabria, told SINC.
"It is much more abundant in granite areas, such as Torrelodones and other areas in the west of the Iberian Peninsula, such as parts of Galicia, Salamanca and Cáceres", he added.
The study conducted in Transylvania, Romania, where there are old uranium mines, showed higher incidence of lung cancer, almost 116.82pct higher than estimates.
The researchers suggest regular checking of gas levels along with ventilating cellars and basements with extractor fans (opening windows alone may not be sufficient, depending on the levels of the gas).
The construction of architectural barriers that are impermeable to radon is also recommended, above all in newly-built houses.
The study appears in journal Science of the Total Environment.