Table 1.

Annual maximum permissible dose according to the National Council on Radiation Protection (NCRP) and measurements for occupational radiation exposure [20] and the International Commission on Radiological Protection (ICRP) [22]

Area/Organ	NCRP annual maximum permissible dose	ICRP annual maximum permissible dose
Thyroid	50 rem (500 mSv)
Extremities	50 rem (500 mSv)
Gonads	50 rem (500 mSv)
Lens of the eye	15 rem (150 mSv) in 1993	20 mSv, averaged over 5 yearsa
	50 mGy (50 mSv) : change in 2018b
Whole body	5 rem (50 mSv)
Pregnant women	0.5 rem (5 mSv)

Adapted from National Council on Radiation Protection and Measurements (Limitation of exposure to ionizing radiation: recommendations of the National Council on Radiation Protection and Measurements; 1993. pp 1-86) [20].

^aIn 2011, the ICRP reduced this dose to 20 mSv per year, averaged over 5 years, with no single year exceeding 50 mSv [22].

^bIn 2018, NCRP reduced the annual maximum permissible dose of occupational exposure in the lens of the eye from 150 mSv to 50 mSv [26].