Radon in homes

Problem

Why does radon-222 (half-life $T_{1/2} = 3{,}8\ \text{days}$) pose a health risk in poorly ventilated homes, despite its very short mean lifetime?

Solution

Radon is a noble gas produced continuously by the decay of uranium present in the soil and in many building materials. Being a gas, it rises from the ground and seeps into buildings; if the indoor air is not exchanged, it accumulates until it reaches a dynamic equilibrium in which the amount produced equals the amount that decays, stabilising however at a high concentration.

The short mean lifetime does not reduce the danger: on the contrary, it means that a large number of $\alpha$ decays occur per unit time. If the gas is inhaled, radon (and its radioactive daughters) decays inside the lungs, emitting $\alpha$ particles, which have a high radiation weighting factor ($w_R = 20$): despite their short range, they deposit all their energy locally and severely damage lung tissue, increasing the risk of lung cancer.

The practical remedy is simple and effective: ventilate rooms, so as to prevent the gas from accumulating.

$\ev{\text{gas that accumulates; }\alpha\text{ particles in the lungs after inhalation}}$

Collegamenti

Argomenti: Fisica nucleare Concetti: Decadimento radioattivo