radon
Meaning of radon: Nothing about the gas can be sensed, so the only way to learn whether a building holds it is to measure the air.
Definition of radon
Radon is a radioactive gas formed as uranium in soil and rock breaks down. It has no color, smell or taste, and it seeps out of the ground into buildings, where it can build up in enclosed spaces. Breathing it in over long periods damages the cells lining the lungs, and it is recognized as a major environmental cause of lung cancer.
How does the gas get indoors?
Uranium is present in ordinary rock and soil almost everywhere, and as it decays it passes through radium and then to radon. Being a gas, radon diffuses upward through soil and reaches the surface. A heated building sits at slightly lower pressure than the ground beneath it, so it draws that soil gas in through cracks in a slab, gaps around pipes and drains, sump openings and unsealed dirt floors. Levels differ enormously between neighboring houses because they depend on local geology, on how the foundation is built and on how much air the building exchanges with outside. Basements and ground floors read highest, readings swing with weather and season, and well water drawn from certain rock can add a further contribution.
Why does an unreactive gas cause cancer?
Radon itself is chemically inert and most of what is inhaled is simply breathed out again. The harm comes from what it turns into. Radon decays within days into short lived solid particles that attach to dust and moisture in the air, and those particles lodge in the lining of the airways. There they emit alpha particles, a form of radioactive emission that travels only a fraction of a millimeter but deposits its energy densely, breaking both strands of DNA in the few cells it reaches. Repair of that kind of damage is error prone, and errors accumulating in airway lining cells are the route to lung cancer.
What changes the size of the risk?
| Factor | Effect |
|---|---|
| Concentration and years of exposure | Risk rises with both, with no level identified below which risk falls to zero |
| Smoking | Multiplies the radon risk rather than adding to it, so smokers carry far the larger share of cases |
| Ventilation and sealing | Venting soil gas from beneath the slab and sealing entry points lowers indoor levels substantially |
Overall, radon ranks behind tobacco as a cause of lung cancer and stands as the leading cause among people who have never smoked, which places it alongside environmental tobacco smoke as an exposure people encounter at home without choosing it. Because concentrations rise and fall from day to day, a measurement taken over months describes a building better than a short one.
Used in a sentence
Radon testing of the home was recommended given the patient's history of lung cancer despite no history of smoking.
Good to know
Radon exposure carries a greater lung cancer risk when combined with smoking than either factor alone would suggest, since the two appear to act together rather than simply adding their separate effects.
Word origin
Where “radon” comes from
Named after radium, the element whose breakdown produces it, with the ending -on shared by the noble gases.