Background Radiation
The ionising radiation always present in the environment from natural and artificial sources.
Unit
mSv/year
In depth
Roughly half of the natural background comes from radon gas seeping from the ground, with the remainder from cosmic rays, from radionuclides in rocks and building materials, and from potassium-40 within the body itself. Any measurement must be corrected for it.
Examples in the real world
A global average of 2.4 mSv per year, far higher in granite regions where radon accumulates indoors.