Fraction of Energy Absorbed from β-Emitting Particles in the Rat Lung

Abstract

Forty-four male Fischer-344 rats were exposed, nose only, to a relatively insoluble aerosol of /sup 144/Ce-labeled fused aluminosilicate particles. Fractional ..beta.. energy absorption was measured 7 to 9 days after exposure for 28 rats (ages 12 to 25 weeks and body weights of 183 to 337 g); lung burdens were 13 to 82 nCi. An additional group of 16 rats was exposed when 12 weeks old and maintained for 6 months prior to analysis; body weights and lung burdens 6 months after exposure ranged from 276 to 368 g and 16 to 46 nCi, respectively. Lungs were carefully removed, inflated, and frozen by immersion in liquid nitrogen. The energy spectrum from each lung was measured in a 4..pi.. ..beta.. spectrometer, keeping the lung frozen throughout this procedure. Over the range of lung sizes in this study (0.88 to 1.66 g) the mean fractional energy absorption and standard deviation were 0.23 +- 0.078, respectively. Results agreed well with theory, indicating that calculated values for fractional energy absorption in the lung can be used for a range of lung sizes and ..beta.. energies. Calculated values for fractional energy absorption as a function of ..beta.. energy are included for several lung sizes betweenmore » 0.5 and 10 g.« less