The work of Laskin, et al, thou:a not specifically involving deep respiratory tissue, does demonstrate a source 4 ; intensity-respense curve for lung tissue 9 A Ru-1O06 cylindrical source was implanted in the bronchi of rats, and cancers were observed to arise from the bronchial epithelium. The response curve indicates a substantial response (7 percent) even at 0.003 uCi burden, and a slow, approximately logarithmic increase of tumor incidence over three orders of magnitude 4 i Fy Corresponding first-year doses to +4ee oe Saad in the source intensity. adjacent bronchial epithelium varied from 103 rad to 106 raa>’, Animals were followed until death and it was observed that the tumor incicence generally increased with the dose accumulated at death. The Lowest accumulated dose associ cancer was 14°79 rad. For an accumulated dose of the order of 106 rad the incidence was approximately two-thirds. = we eee fortified glass seads of Sr-90, rats. (0.3 u diameter) with several microcuries and single beads were Tumers were Cember observed in implanted in the lungs of 7 of 23 animals. In a second deer Cle experiment Cerber exnosed rat lungs to Ce-144 particles. 49/ Laskin, S., M. Kuschner, N. Harley and M. Daniels, Nelson, For B. Altshuler, J.H. "Carcinoma of the lung in rats exposed to the beta-radiation of intra-bronchial rutheniuml%6 pellets. 1. Dose response relationshivos," J. 2a omee 1963, pp. 219-231. 50/ Altshuler, B., "Dosimetry pellet," Radiation Res. 9, Natl. Cancer Inst. 31, from a Rul96_-coated olatinum 1958, pp. 626-632. s la NEO gg UME Tr At Oa vg