Noun
millisievert (plural millisieverts)
(physics) A unit of ionizing radiation equal to 10 sieverts
The worldwide average natural dose to humans is about 2.4 millisievert (mSv) per year. Source: Internet
Usually ranging from 1 millisievert (mSv) to 13 mSv annually depending on location, average radiation exposure from natural radioisotopes is 2.0 mSv per person a year worldwide. Source: Internet