Short-lived radioactive decay products of radon that include 216-Po, 214-Pb, 214-Bi, and 214-Po. They have an effective half-life of about 30 minutes and are solids that can deposit on the bronchial airways during inhalation and exhalation. This results in exposure of the respiratory airways to alpha radiation and can lead to diseases of the respiratory system, including lung cancer. (From Casarett and Doull's toxicology, 4th ed, p740)