The very word “radiation” can evoke horror. Since this word was first used in connection with the use of nuclear weapons at the end of the Second World War, radioactivity in our minds has always been associated with great destructive power. Since then, we have been living under the threat of nuclear conflict. Over the past ten years, especially after the Chernobyl accident, people have become aware of the completely destructive power that radiation brings with it. So what is radiation? How does radiation contamination occur? How does it spread? What are the consequences of radioactive contamination? What can be done to limit it? Below we will talk about the negative effects of radiation and the precautions that people living in areas of potential risk of radioactive contamination should take. These facts need to be known because every person is daily exposed to natural radiation - cosmic radiation, radiation from soil and food. Some people may also receive therapeutic doses of radiation from X-rays or X-rays for treatment.