- 50 the value selected by Kathren be used when the RF is unknown to Getermine the ambient ground contamination standard. Applying an RF=10-4 m7! to the ambient MPCa standard recommended in the previous section, we obtain a maximum per- missible surface contamination (MPCS) level for hot particles of 9x1078 nci/m2. °° This is roughly 1 hot particle/m@. tn areas where an RF greater or less than 1074 m1 could be shown to apply, the MPSC could be altered appropriately. E As Low as Practicable Hearinas It is to-be uncerstood that the above recommendations do not represent endorsementon Our part of the risk inherent in the existing radiation protection guidelines upon which these recommendations are based. Rather, we offer the admonition that the exposures should be kept as far below these guidelines as is practicable. ‘Therefore, we further recommend that these guidelines be incorporated into the existing regulations without delay and that the ‘appropriate agency or agencies convene hearings to determine for the regulations what constitutes as low as practicable Jimits for exposure to hot particles. 86/ This value is derived as follows: The recommended MPCs, for not particles is 9x10718 uci/ml which ccrresronds to 9x10-12 uci/m3. The manimum ground contamination level, using RF=1074 r7+, is 9xlo-l2/io-i = Gx1078 uCi/’n2.