ABSTRACT
There is little difference between the analysis of risk from ionizing radiations and that from chemicals. Modes and pathways of exposure must be considered as well as concentrations and length of exposure. The differences from chemical exposures are particularly important, not the least being regulatory methods of limiting risk.
An important difference is that dose is dependent on the type of radiation. Types of radiation are limited but the differences in how the types of radiation interact with tissue are important in determining the dose and risk. Regardless of the type of radiation or radionuclide that is the source of radiation, dose or effective dose is applied in risk analysis in a simple linear equation.
The next important difference is that although risk is simply determined from dose, dose is the quantity used in regulation of radiation. Dose is the regulatory limit partly because effects were historically compared to measured dose and acceptable dose was considered in relation to the dose from natural radiation in the environment.
Several important distinctions in how dose is received determine both limits and methods of calculation. These distinctions are external dose, internal dose, effective dose, and population dose.
External dose is dose received from radiation outside the body.
Internal dose is dose received from radionuclides deposited in the body.
Effective dose is a means of equating external and internal dose to the same measurement quantity. Different types of radiation may have different effective doses even when the same amount of energy is deposited in the body. Even the same type of radiation may deliver different effective doses for the same amount of energy deposited if the energies of the radiations differ. Population dose is individual dose summed over a population. In general, the regulatory limit for population dose is risk rather than dose.
164Methods for calculating dose follow conventions developed by national and international committees on radiation protection. Many of these conventions follow idealized schemes for which modifying methods have been developed depending upon the radiation type, energy, and method of receiving the dose.
