Radiation Effects and Sources

What is Radiation? What does Radiation do to us? Where does Radiation come from?

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This publication is based on the major scientific reports of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) published in the last 25 years and aims to expand public knowledge on levels of exposure to ionizing radiation and possible associated effects. This publication does not set, or even recommend, radiation safety standards, rather, it provides information on basic science related to radiation (origin, quantities and units), on radiation effects (on humans and the environment) and on radiation sources (natural and artificial). Helping the public understand what radiation is and how it affects life on this planet lies within the core mandate of UNEP.



Where does Radiation come from?

We are continuously exposed to radiation from many sources. All species on Earth have existed and evolved in environments where they have been exposed to radiation from the natural background. More recently, humans and other organisms have also been exposed to artificial sources developed over the past century or so. Over 80 per cent of our exposure is from natural sources and only 20 per cent is humanmade from artificial sources—mainly from radiation applications used in medicine. Radiation exposure is categorized in this publication by its sources, with a focus on what the general public receive. For regulatory purposes (e.g. radiation protection) radiation exposure is addressed for different groups. Therefore, additional information is provided here on patients—who are exposed due to medical use of radiation—and on people exposed at workplaces.


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