You can't see it. You can't smell it. You can't taste it. But radon might be in your basement right now. It's a radioactive noble gas that seeps through cracks in your home's foundation. According to the WHO, radon is the second leading cause of lung cancer after smoking. It kills thousands of people every year worldwide.
Radon forms when radium-226 in rocks and soil decays. The most stable isotope has a half-life of just 3.8 days. This gas is 7.5 times heavier than air, so it pools in low places: basements, ground floors, mines. German chemist Friedrich Dorn discovered it in 1900 while studying radium's emissions.
Radon belongs to the noble gas family, but it's the only one with zero stable isotopes. All 39 known radon isotopes are radioactive. When it decays, it produces polonium-218 and other dangerous "daughter" products that stick to dust particles and enter your lungs.
Here's a paradox: some countries use radon baths to treat arthritis. Austria and Japan have radon caves where patients come for therapy. But most doctors consider this risky, and the WHO warns that any radiation dose increases cancer risk.
Radon is a serious health threat. You cannot see, hear, or smell it. It enters homes through foundation cracks and accumulates in poorly ventilated spaces. Its decay products (polonium, lead, bismuth) lodge in lungs and irradiate tissue. Safe level is below 100 Bq/m³ (2.7 pCi/L). Above 150 Bq/m³ (4 pCi/L) — take action. Test your home for radon. It's cheap and could save your life.
Radon is the second leading cause of lung cancer worldwide. The EPA estimates it causes about 21,000 deaths per year in the US alone.
Radon is 7.5 times heavier than air. It's the heaviest naturally occurring gas, so it sinks and collects in basements.
Radon is everywhere: it seeps from soil across the entire planet. Levels depend on geology — highest where there's granite and volcanic rock.
Radon-222 has a half-life of just 3.8 days. Within a month, less than 0.01% of the original amount remains.
Medieval miners died en masse from 'mountain sickness' — lung cancer. It wasn't until the 20th century that scientists realized radon was the cause.
Radon can glow yellow, and when cooled further, it turns bright orange and red due to its own radioactive emissions.
| Isotope | Mass (u) | Abundance | Half-life | Decay |
|---|---|---|---|---|
211Rn☢ | 210.990601 | synthetic | 14.6 hours | α |
220Rn☢ | 220.011394 | synthetic | 55.6 seconds | α |
222Rn☢ | 222.017578 | synthetic | 3.8235 days | α |
Radioactive decay of radium