Risk Evaluation: Methodological Reforms

A naturally occurring decay product of radium 226, radon 222 has an important impact on human health. Because it can leave the soil or rock in which it is present and enter the surrounding air or water, radon gas is ubiquitous. When it decays into a series of radioisotopes collectively referred to as “radon daughters,” two of these daughters (polonium 218 and polonium 214) give off alpha particles. These alpha particles, when emitted in the lung, can cause lung cancer.¹ Until recently, radon daughter exposure was associated with lung cancer in uranium miners. Now we know that radon daughters are