Scab diameters on pig skin resulting from hot particle exposures under varying conditions

The National Council on Radiation Protection and Measurements (NCRP) in NCR P Report Number 106 recommended a limit of 10(10) beta particles emitted fr om radioactive particles with sizes less than 1 mm (hot particles) to preve nt acute deep ulceration. This recommendation was determined, in part, by r egressing the diameter of the scabs induced by fissioned (UC2)-U-235 hot pa rticles as a function of the logarithm of the number of beta particles emit ted from the sources for one study. To validate this recommendation and the approach used by the NCRP, external irradiations of pig skin using radioac tive sources of less than 600 mum in the largest dimension were carried out . The hot particles used included fissioned (UC2)-U-235 and activated Tm-17 0, Yb-175, and Sc-46. Results indicated a strong correlation between scab d iameter and dose for scabs induced using fissioned (UC2)-U-235, activated T m-170, and Sc-46, but not for Yb-175. The correlation value decreased with decreasing beta particle energy, with the exception of Sc-46, which had sca bs with diameters greater than twice the maximum beta particle range, The l arger scabs from Sc-46 are thought to be due to dose contributions from the gamma rays. The results also give an ulceration threshold less than that g iven by NCRP to prevent acute deep ulceration. It was concluded that regres sion analysis of scab diameter as a function of either number of beta parti cles emitted from the hot particles or dose did not yield either precise or accurate thresholds but was useful in determining probable ranges of doses which lead to scab induction.