Radon and its by-products are by far the greatest single source of radiation that we receive in our lifetime. More than from medical testing, cosmic sources, and consumer products combined. Breathing air that contains radon increases the risk of lung cancer. Other than smoking, radon exposure is the leading cause of lung cancer.
Cumulative Radiation Exposure for the Average US Citizen
Radon comes from the natural decay of uranium present in the soil and bedrock. This uranium is present in varying concentrations around the US, and thus radon levels also vary widely even among homes within the same neighborhood. Radon is naturally present outdoors as well, albeit in small concentrations of around 0.4 piC/l. Higher concentrations of radon in indoor air make up the bulk of our exposure. As radon comes from the ground, concentrations are higher in the lower levels and dissipate significantly as elevation within a structure increases.
Small amounts of radon are also present in ground water, and can cause exposure either through drinking contaminated water, or inhaled as water vapor during a shower. This type of exposure is much less common. If high levels of radon are detected in the air, you may wish to test your well water supply as well. The Environmental Protection Agency (EPA) provides fact sheet for Radon in drinking water.
Radon testing measures the levels of radon and its radioactive decay by-products, or “radon progeny”. Radon will eventually decay down to a stable lead isotope, giving off alpha and beta radiation along the way.
| Isotope | Half-Life | Radiation |
| Radon 222 | 3.8 Days | Alpha |
| Polonium 218 | 3 Minutes | Alpha |
| Lead 214 | 27 Minutes | Beta |
| Bismuth 214 | 20 Minutes | Beta |
| Polonium 214 | 180 Microseconds | Alpha |
| Lead 210 | 22 Years | Beta |
| Bismuth 210 | 5 Days | Beta |
| Polonuim 210 | 138 Days | Alpha |
| Lead 206 | STABLE | None |