What are common sources of radiation categorized as 'natural'?

Natural sources of radiation primarily come from the environment and can be categorized into three main categories: atmospheric, terrestrial, and internal.

Atmospheric radiation includes cosmic rays that originate from outer space and constantly bombard the Earth. Terrestrial radiation comes from radioactive materials in the Earth's crust, such as uranium, thorium, and radon gas, which emanates from the soil and building materials. Internal radiation refers to the radioactive isotopes that are naturally present within the human body, primarily from the food we consume and the air we breathe, such as potassium-40 and carbon-14.

Understanding that these sources are part of our natural surroundings is crucial in the field of radiation safety, as it provides a baseline for distinguishing between natural and artificial sources of radiation when assessing exposure and implementing safety measures.