HEMATOLOGICAL EFFECTS OF INHALED PLUTONIUM DIOXIDE IN BEAGLES

A life-span study indicated that plutonium activity in the thoracic ly mph nodes is a contributor to development of lymphopenia in beagles ex posed to (PuO2)-Pu-239. Significant lymphopenia was found in 67 (58%) beagles given a single nose-only exposure to (PuO2)-Pu-239 to result i n mean initial lung depositions ranging from 0.69 to 213.3 kBq. Lympho id atrophy and sclerosis of the thoracic lymph nodes and lymphopenia w ere observed in exposure-level groups with initial lung depositions gr eater than or equal to 2.5 kBq. Those dogs with final plutonium concen trations in the thoracic lymph nodes greater than or equal to 0.4 kBq/ g and dose rates greater than or equal to 0.01 Gy/day developed lympho penia. Marked differences existed between chronically lymphopenic dogs and intermittently lymphopenic dogs with regard to initial lung depos ition, time to lymphopenic events and absolute lymphocyte concentratio ns. Linear regression analysis revealed moderate correlation between r eduction in lymphocyte values and initial lung deposition, in both mag nitude and time of appearance after exposure. Cumulative dose and dose rate appeared to act together to produce initial effects on lymphocyt e populations, while dose rate alone appeared to be responsible for th e maintenance and subsequent cycles of lymphopenia seen over the life span. No primary tumors were associated with the thoracic lymph nodes in this study, although 70% of the lymphopenic dogs developed lung tum ors. (C) 1995 by Radiation Research Society