Ionizing radiation damages living tissues and organisms. Its effect on life depends on the type of radiation, the rate at which the radiation is received, and dosages (amounts) of radiation received. The (tradional) cgs unit for dose is roentgen equivalent man (rem) whereas the SI unit for it is the sievert (1 Sv = 100 rem).
How much natural radiation do we receive each year? What doses are we receiving in a dental or chest examination? To make sense of answers these questions, we need to understand the quantities or dose units in radiation measurements.
Early X-ray and uranium workers suffer dermatitis, skin lesions, lung cancers and other occupational diseases. The danger of radiatin exposure was realized soon after their discovery. There was a collective response to these risks.
The NCRP has been responsible for setting the guidelines for safe operation procedures for the U.S.A. from the experience learned from the health physics group.