International and US radiation protection standards are based upon risk assessment and risk management processes. The assessment of radiation risk is derived from the linear no-threshold (LNT) model. Risk management is based on more subjective value judgements. If the radiation dose-response was found to be hormetic, considerable quantitative data would be needed before current radiation protection standards would change. There would be added complexity, and consideration might have to be given to the additive effects of an individual's exposures to medical radiation and other potential carcinogens.
As a regulatory agency the US Nuclear Regulatory Commission's (NRC) mission is to protect public health and safety and the common defense and security of the USA. One of the NRC's tasks is to ensure the safety and health of workers and the public from exposure to ionizing radiation from the use of those nuclear materials regulated under the Atomic Energy Act. The task of ensuring safety requires the NRC to take two actions. The first is to determine the risk from exposure to ionizing radiation, and the second is to establish the acceptability of the risk. These are usually referred to as risk assessment and risk management and they should not be confused. Risk assessment tends to be the more objective and scientific, whereas risk management is value-laden and strongly affected by societal and ethical views.
In the USA, the regulation of ionizing radiation protection standards is spread among a number of state and federal agencies. The scientific bases for radiation protection standards are included in the recommendations of several committees, including: the International Commission of Radiological Protection (ICRP), the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), the United States National Research Council's Committee on the Biological Effects of Ionizing Radiation (BEIR) and the National Council on Radiation Protection and Measurements (NCRP). The assessment of risks from ionizing radiation by all of these committees is based on the linear no-threshold (LNT) model. In this model the stochastic consequences of radiation are considered to be a linear function of dose and, except for one small correction, almost completely independent of dose rate.
The LNT model-the current scientific paradigm for the effect of low-level ionizing radiation-is used by the NRC for assessing radiation risks and performing cost-benefit analyses to assist in determining the consequences of regulatory actions. It is instructive to trace