 These miners inhale radon gas, which then undergoes radioactive decay, emitting an alpha particle This alpha particle traverses the cells of the bronchial epithelium, potentially causing cancer.The average lifetime radon exposure of these miners is high enough that cancer risk estimates are driven by data on individuals whose target bronchial cells are subjected to multiple alpha particle traversals.On the other hand, for an average house occupant, about 1 in 2,500 target bronchial cells will be exposed per year to a single alpha particle, but less than 1 in 107 of these cells will experience traversals by more than one particle.