CURRENT STUDIES ON BIOLOGICAL EFFECTS OF LOW-LEVEL INTERNAL IRRADIATION

The biological effects of relative low level internal irradiation were introduced. 1. Life span studies on carcinogenesis. Pacific Northwest Laboratory observed 3782 rats given a single inhalation of Pu-239 O2 at initial lung burden ranging from 0.25 to 180 nCi. Significant life span shortening was found at lung dose > 8 Gy and it was indicated tha t the presence of a ''possible'' threshold of about 1 Gy for lung tumo r formation. 2. Health effects of radon and its progeny. Both experime ntal and epidemiological survey were studied. The nominal probability coefficient (fatality) for the public and workers are 7.90 x 10(5) per mJhm-3 (2.77 X 10(-4) per working level month, WLM). 3. Health effect s of H-3 on postnatal brain development and neurobehavior, genetic eff ects, carcinogenic effects and adaptive effects of H-3 were investigat ed. 4. Study on the effects of neuroendocrine system under low level i rradiation of Se-75 (Auger electron emitter) and S-35 (beta-particles emitter). The results showed that the neuroendocrine system is very se nsitive to small dose of internal irradiation.