The sources of radiation are divided into two main categories: natural and man-made. Radiation has always been a natural part of the environment.
Man-made radiation has been emitted for about 150 years since the inventions of the industrial revolution went into widespread use, now we’re part of the digital revolution. Artificial sources of radiation are claimed to be responsible for about 15% of the total exposure. An even higher level of exposure (50%) may affect industrialized countries due to the more widespread access to technology.