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

External irradiations of pig skin using radioactive sources of less than 600 mum in the largest dimension (hot particles) were carried out. The objective of the study was to determine a threshold for scab induction. Hot particles used included fissioned U-235 and activated Tm-170, Yb-175, and Sc-46 with maximum beta-particle energies of similar to1.8 (average), 0.97, 0.47, and 0.35 MeV, respectively. The photon emissions from the fissioned U-235 were about 1 MeV per disintegration. The photon emissions from Sc-46 were 0.89 and 1.12 MeV, with 100% abundance. Photon emissions from Tm-170 and Yb-175 were negligible. Responses followed cumulative normal probability distributions; thus, no true thresholds could be determined. Hence, 10% and 50% scab incidence rates (ED10 and ED50, respectively) were determined using probit analysis. For dose averaged over 1 cm(2) at a depth of 70 mum, the ED10 (and 95% confidence limits) were 5.1 (2.7-7.2) Gy for Sc-46, 1.3 (0.89-1.8) Gy for Yb-175, 2.8 (1.9-3.5) Gy for Tm-170, 8.5 (5.7-9.8) Gy for on-skin fissioned UC2, and 4.5 (0.9-7.2) GS for off-skin fissioned UC2. The ED50 values were 12 (8.8-17) Gy for Sc-46, 6.0 (4.3-9.7) Gy for Yb-175, 5.9 (5.1-6.7) Gy for Tm-170, 11 (9.9-19) Gy for on-skin fissioned (UC2)-U-235, and 11 (6.2-14) Gy for off-skin fissioned (UC2)-U-235.