What are the sources of ionizing radiation. i heard its dangerous thanks?

Good question: 80% of global average exposure of humans to ionizing radiation comes from nature (cosmic radiation, radon gas...). The remaining 20% results from exposure to human made radiation sources like medical imaging, air travel and nuclear power plant to mention a few. In medical imaging today in particular there is a big empahsis on reducing the radiation dose to as low as reasonably achievable.

It is everywhere: Ionizing radiation is everywhere. We get it from the sun, the air and the water but it is in very small doses. Sources include Radon, Cosmic radiation, polonium, and medical procedures that use isotopes and x-rays. The doses we receive from medical exams can be much higher than this "background" radiation. Ionizing radiation can damage DNA when the doses are large. check out Radiologyinfo.org.