 The effects of radiation on living tissue is a consequence of the ionization. Ionized atoms inside cells can disrupt chemical processes, break chemical bonds, or even destroy DNA and kill the cell. While higher energy deposition results in an increased dose and risk to the living tissue, there is an additional factor that comes into play. This is the fact that different types of radiation deposit their radiation in different patterns. In particular, heavy charged particles like an alpha particle result in a very dense ionization track, while gamma rays and electrons, that is beta radiation, result in a relatively sparse ionization track, with gaps between the interaction points. As illustrated in the picture, it is clear that a very dense track has a greater chance of disrupting the important machinery of a living cell. In fact, the radiation dose produced from equivalent energy depositions of alpha particles compared to beta or gamma radiation differ in their effect on living tissue by a factor of almost 20. As well as the immediate death of a cell from ionizing radiation, there is also a possibility that changes to the DNA inside a cell can cause a mutation or cancer. While a larger amount of radiation has a direct causal relationship leading to increased cell deaths and, in the case of large doses, possible radiation sickness or death of an individual, the second type of effect leading to mutations and cancers are intrinsically random and cannot be predicted for any specific exposure to radiation. When thinking about radiation, it is important to consider how to control exposure through appropriate shielding. This depends upon the type of radiation as shown in the figure on the right. Alpha radiation is not very penetrating, and it is typically stopped by a piece of paper, a small amount of air, or even the dead layer of external skin. In fact, it is almost impossible for an alpha decaying radioisotope to be dangerous unless the radioisotope is ingested or breathed in. However, as noted on the left, once ingested, the alpha radiation is 20 times more dangerous than the same energy of beta or gamma radiation. On the other hand, beta radiation is more penetrating and can certainly create damage to living tissue from external exposure. Relatively thick plastic or light metals such as aluminium are the minimum shielding required to stop beta radiation. Gamma radiation, particularly high-energy gamma ray photons, are exceedingly penetrating and are best shielded by heavy metals such as lead. Note that a high-energy photon can quite easily pass most of the way through your body before interacting deep inside.