Dosimetric considerations for environmental radiation and NORM

The physical theory of dosimetry for environmental radiation, including radiation emitted from naturally occurring radioactive materials (NORM), is no different than that required in any other setting where doses are estimated. However, the application of such theory to environmental radiation and NORM may require considerations that differ from dose estimation elsewhere. This is especially true if the intent is to provide estimated doses for epidemiologic analyses. It should be realized that metrics of radiation dose for radiation protection purposes are generally not the same as for analytic epidemiologic studies which require estimates of absorbed dose to specific organs of identified persons. In addition, exposures to environmental radiation and NORM typically involve radiation fields that vary considerably over space, and the patterns of an individual's movements, as well as the types of buildings in which they reside and work, can significantly affect the dose received from external radiation. Realistically describing the spatial variation of environmental exposure rates is a difficult challenge for environmental dosimetry, rather than the physical principles that are relatively well understood. This publication will review these ideas in the context of improving estimated doses from high background radiation studies.