CARCINOMA OF THE UPPER RESPIRATORY-TRACT IN RATS FOLLOWING NOSE-ONLY INHALATION OF (PUO2)-PU-239

A total of 3157 female Wistar, 198 male Wistar, 200 female F344 and 19 2 female Long-Evans sham-exposed and exposed young adult rats were exa mined for distribution of plutonium and tumors in the upper respirator y tract following inhalation of high-fired (PuO2)-Pu-239. A small numb er of inhaled (PuO2)-Pu-239 particles were retained for long periods i n subepithelial regions of the larynx and nasal cavity. These particle s contributed a small fraction of the total dose to airway epithelium. No tumors were found originating from the trachea or larynx. One nasa l cavity tumor was found in a control female Wistar rat (0.095%) while five tumors were found in exposed female Wistar rats (0.24%). Two nas al cavity tumors were found in exposed female Long-Evans rats (1.5%), while no nasal cavity tumors were found in control Long-Evans rats or in control or exposed female F344 or male Wistar rats. Nine oral squam ous cell carcinomas were distributed among control and exposed Wistar rats of both genders; these tumors all appeared to be associated with malocclusion of incisor teeth. No oral carcinomas were found in F344 o r Long-Evans rats. Only in the nasal cavity was a possible association found between inhaled (PuO2)-Pu-239 and tumor formation in the upper respiratory