Background. Extensive research on the health effects of radiation using standard epidemiological and toxicological approaches has been done for decades to characterize responses of populations and individuals to high radiation doses, and to set exposure standards to protect both the public and the workforce.
These standards were set using models that extrapolated from the cancers observed following exposure to high doses of radiation to predicted, but not measurable, changes in cancer frequency at low radiation doses.
The use of models was necessary because of our inability to detect changes in cancer incidence following low doses of radiation. Historically, the predominant approach has been the Linear-no-Threshold model (see Wikipedia entry) and collective dose concept that assumes each unit of radiation, no matter how small, can cause cancer. As a result, radiation-induced cancers are predicted from low doses of radiation for which it has not been possible to directly demonstrate cancer induction.
Sources of low dose radiation: Over the next 100 years, low dose radiation exposures are expected to be from medical tests, waste clean-up activities, terrorism events (e.g., dirty bombs) and environmental isolation of materials associated with nuclear weapons and nuclear power production.
Focus of program studies: The major type of radiation exposures will be low Linear Energy Transfer (LET) ionizing radiation (primarily X- and gamma-radiation) from fission products. Thus, the Low Dose Program will concentrate on studies of low-LET exposures delivered at low total doses and low dose-rates.
The research program involves using advances in modern molecular biology and instrumentation unavailable during the previous 50 years of radiation biology research. Scientists will be able to examine—at a systems level—the relationship between normal oxidative damage and radiation-induced damage, using studies conducted at very low doses and dose-rates.
The radiation-induced perturbation of normal physiological processes, along with the biological system's homeostatic responses will eventually be characterized at all levels of biological organization—from genes to cells to tissues to organisms.