Background radiation equivalent time BRET value corresponding to a dose of radiation is the number of days of average background dose it is equivalent to. It is calculated from the equivalent dose in sieverts by dividing by the average annual background radiation dose in Sv, and multiplying by 365: The definition of the BRET unit is apparently unstandardized, and depends on what value is used for the average annual background radiation dose, which varies greatly across time and location. The 2000 UNSCEAR estimate for worldwide average natural background radiation dose is 2.4 mSv (240 mrem), with a range from 1 to 13 mSv. A
International Commission on Non-Ionizing Radiation Protection medicine, physics and dosimetry and optical radiation. Its members are scientists employed typically by universities or radiation protection agencies. They do not represent their country of origin, nor their institute and can not be employed by commercial companies. ICNIRP is widely connected to a large community working on non-ionizing radiation protection around the world. Its conferences and workshops are widely attended. ICNIRP presents its draft guidelines online for public review and comment before publication. It has ties to IRPA and is formally recognized by the World Health Organization (WHO) and the International Labour Office (ILO) as partners in the field