Toxicity of plutonium

Tamplin and Cochran evaluated the rate of carcinogenetic action of ununiform exposure with PuO2 particles deposited in the lungs and suggested to reduce the present standard of plutonium to 1/115,000. The author examined the management of ununiform exposure based on various views and appraised the risk. The number of ''permissible'' particles for occupational exposures with the risk of 1/1,000 in a year was found to be 2s-2 or 25d-6 for personal and 0.2s-2 or 2.5d-6 for the general public against a particle with radioactivity of S pCi and diameter of dμ. This result essentially supported the suggestion of Tamplin and Cochran. (Tsukamoto, Y.)