How often does it happen? A review of unintended, unnecessary and unavoidable high-dose radiation exposures.

High-dose radiation exposures of humans occur every year around the world, and may lead to harmful tissue reactions. This review aims to look at the available information sources that can help answering the question of how often these events occur yearly on a global scale. In the absence of comprehensive databases of global occurrence, publications on radiation accidents in all uses of radiation and on rates of high-dose events in different medical uses of radiation have been reviewed. Most high-dose radiation exposures seem to occur in the medical uses of radiation, reflecting the high number of medical exposures performed. In therapeutic medical uses, radiation doses are purposely often given at levels known to cause deterministic effects, and there is a very narrow range in which the medical practitioner can operate without causing severe unacceptable outcomes. In interventional medical uses, there are scenarios in which the radiation dose given to a patient may reach or exceed a threshold for skin effects, where this radiation dose may be unavoidable, considering all benefits and risks as well as benefits and risks of any alternative procedures. Regardless of if the delivered dose is unintended, unnecessary or unavoidable, there are estimates published of the rates of high-dose events and of radiation-induced tissue injuries occuring in medical uses. If this information is extrapolated to a global scenario, noting the inherent limitations in doing so, it does not seem unreasonable to expect that the global number of radiation-induced injuries every year may be in the order of hundreds, likely mainly arising from medical uses of radiation, and in particular from interventional fluoroscopy procedures and external beam radiotherapy procedures. These procedures are so frequently employed throughout the world that even a very small rate of radiation-induced injuries becomes a substantial number when scaled up to a global level.