Carcinoma of the Upper Respiratory Tract in Rats Following Nose-Only Inhalation of 239 PuO 2

ABSTRACT

A total of 3157 female Wistar, 198 male Wistar, 200 female F344 and 192 female Long-Evans sham-exposed and exposed young adult rats were examined for distribution of plutonium and tumors in the upper respiratory tract following inhalation of high-fired ²³⁹puO₂. A small number of inhaled ²³⁹puO₂ particles were retained for long periods in subepithelial regions of the larynx and nasal cavity. These particles contributed a small fraction of the total dose to airway epithelium. No tumors were found originating from the trachea or larynx. One nasal 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 nasal 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 squamous 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 or Long-Evans rats. Only in the nasal cavity was a possible association found between inhaled ²³⁹puO₂ and tumor formation in the upper respiratory tract.