the whole body. To take this into account, the effective doses to the component parts of the body which have been irradiated are calculated and summed. This becomes the effective dose for the whole body, dose quantity . It is a "protection" dose quantity which can be calculated, but cannot be measured in practice. An effective dose will carry the same effective risk to the whole body regardless of where it was applied, and it will carry the same effective risk as the same amount of equivalent dose applied uniformly to the whole body. Usage for internal dose Effective dose can be calculated for committed dose which is the internal dose resulting from inhaling, ingesting, or injecting radioactive materials. The dose quantity used is: Committed effective dose, is the sum of the products of the committed organ or tissue equivalent doses and the appropriate tissue weighting factors , where is the integration time in years following the intake. The commitment period is taken to be 50 years for adults, and to age 70 years for children. Calculation of effective dose Ionizing radiation deposits energy in the matter being irradiated. The quantity used to express this is the absorbed dose, a physical dose quantity that is dependent on the level of incident radiation and the absorption properties of the irradiated object. Absorbed dose is a physical quantity, and is not a satisfactory indicator of biological effect, so to allow consideration of the stochastic radiological risk, the dose quantities equivalent dose and effective dose were devised by the International Commission on Radiation Units and Measurements (ICRU) and the ICRP to calculate the biological effect of an absorbed dose. To obtain an effective dose, the calculated absorbed organ dose is first corrected for the radiation type using factor to give a weighted average of the equivalent dose quantity received in irradiated body tissues, and the result is further corrected for the tissues or organs being irradiated using factor , to produce the effective dose quantity . The sum of effective doses to all organs and tissues of the body represents the effective dose for the whole body. If only part of the body is irradiated, then only those regions are used to calculate the effective dose. The tissue weighting factors summate to 1.0, so that if an entire body is radiated with uniformly penetrating external radiation, the effective dose for the entire body