Low levels of radiation used for medical imaging should not be considered harmful, according to an article published in the American Journal of Clinical Oncology.
The article, by authors from the FDA Center for Devices and Radiological Health in Rockville, MD, and Loyola University in Chicago, IL, sought to examine the origination of the linear no-threshold (LNT) model with respect to genetic effects and carcinogenesis. While this particular model was conceived more than 70 years ago, it remains a foundational element within much of the scientific thought regarding exposure to low-dose ionizing radiation: that any level of radiation, no matter how low, can be harmful.
The authors argue that the general population is exposed to low-dose radiation every day through common activities, due to natural background radiation exposures. The exposure can range from a few mGy to as high as 260 mGy, depending on geographic location. And yet, no related effects have been noted.
People in countries like the U.S. have longer life expectancies, despite this increase in radiation exposure, including that received during medical diagnostics and care. “Yet, the persistent use of the linear no-threshold model for risk assessment by regulators and advisory bodies continues to drive an unfounded fear of any low-dose radiation exposure, as well as excessive expenditures on putative but unneeded and wasteful safety measures,” the authors wrote.
The authors summarize the relevant literature on which the LNT model foundation was based, starting in 1927 with fruit fly experiments, to 1949. They also discuss the data derived from the survivors of the Hiroshima and Nagasaki atomic bomb detonations in Japan, as well as three groups: patients irradiated for ankylosing spondylitis, children irradiated as infants for thymic enlargement, and radiologists.
After reviewing these data, the authors did not come to the conclusion that the studies supported the LNT model, and that the model was invalid for low radiation doses. The original research had been done in fruit flies, which were irradiated at doses far beyond what humans could tolerate, yet this was still used as a basis for the LNT model, the authors noted.
“The application of this model by regulators and advisory bodies around the world has resulted in overly conservative policies and practices that have been responsible for promoting radiophobia and causing actual deaths,” the authors concluded. “The use of the LNT model therefore should finally and decisively be abandoned, although it will take some time for its damaging effects to overcome.”