The danger of radiation from radioactive materials trapped in the soil is slight. If the area is not too extensive it can usually be quarantined temporarily, or permanently if necessary, although plants which might survive in a region with high levels of background radiation can lead to a concentration of radioactive isotopes in the food chain.

Naturally occurring radioactive isotopes in the air emit radiation which is more difficult, and sometimes impossible to control. For example, ₆C¹⁴ (carbon-14) has a half-life of 5,730a. It is produced continuously in the upper atmosphere by the impact of primary cosmic rays.

₆C¹⁴ is a beta emitter which produces a 156keV electron when it decays. Since carbon is ubiquitous, radioactive carbon-14 is found in minute quantities among the carbon-12 atoms that make up every living thing.

Radon gas is also an environmentally important radioactive gas since it tends to accumulate in basements, caves, and become trapped in depressions where air circulation is weak. Frequent exposure to radon gas by breathing it is especially dangerous. The most common isotope of radon is ₈₆Rn²²³, which emits 5.49MeV alpha particles as it decays.

The main contributor to our personal exposure to radiation from terrestrial sources is from potassium-40. Potassium-40 is relatively abundant in nature. Since potassium is also an essential element for our bodies, potassium-40 is a major contributor to out internal radiation exposure.