report; the maximum permissible lung burden (MPLB) and the maximum permissible concentration in air (MPC,). The MPLB is the total amount of a given radionuclide in the lung of an average size man that will result in the lung being irradiated at the maximum permissible lung dose (MPLD). Tne MPC, is the concentration in air that will result in an averace adult male obtaining a MPLB and hence a MPLD by breathing the air. It is important to recognize that the MPLD is the orimary Standard; it applies to all radionuclides and radiation sources. The MPLB and the MPCa are Gerived standards anc are svecitic for a radionuclide. These derived standards are relatsc to the biological properties of a radionuclide ang to the icrm of radiation it emits. Tabie I lists the existing exposure standards for enplovees of the nuclear industry that apply to Pu-239 in insoiudle form. Tas MPLD of 15 ren/vr is included in the recommendations of the International Commission on Radiological Protection 8 (ICRP), the Nacional Council on Radiation Protection and Me2surements (ucap)?, and ion 9, the Federal Radiation Council Retommendations of the Intern2tiona tological Protection (Adosted Sentenbear 17, S$, new fOrk, 1966, p. 14. 9’ NCRP Pavart No. 39, Basic Padiation Protection Criteria, NIPP Publications, Washington, 0. C., Jan. 15, 1971, vo. 196. 1965),