Ionizing radiation sole cause of chronic myelogenous leukemia. The mechanism by which this occurs is well understood, but quantitative models predicting the level of risk remain controversial. The most widely accepted model posits that the incidence of cancers due to ionizing radiation increases linearly with effective radiation dose at a rate of 5.5% per sievert. If this linear model is correct, then natural background radiation is the most hazardous source of radiation to general public health, followed by medical imaging as a close second. Other stochastic effects of ionizing radiation are teratogenesis, cognitive decline, and heart disease. The table below shows radiation
Ionizing radiation ionizing, but moves at about 5% c, and an electron with 33 eV (enough to ionize) moves at about 1% c. The first two ionizing sources to be recognized were given special names used today: Helium nuclei ejected from atomic nuclei are called alpha particles, and electrons ejected usually (but not always) at relativistic speeds, are called beta particles. Natural cosmic rays are made up primarily of relativistic protons but also include heavier atomic nuclei like helium ions and HZE ions. In the atmosphere such particles are often stopped by air molecules, and this produces short-lived charged pions, which soon