Naphthalene: A Respiratory Tract Toxicant and Carcinogen for Mice

Abstract The toxicologic and carcinogenic potential of naphthalene was studied by exposing groups of male and female B6C3F1 mice to atmospheres containing 0 (75 mice per sex), 70 ppm (75 mice per sex), or 30 ppm (150 mice per sex) of the chemical for 6 h daily, 5 dayslwk for 103 wk. The final mean body weights of mice exposed to naphthalene were similar to those of the controls. The survival of control male mice was significantly lower than that of the exposed males. The lower survival was attributed to wound trauma and secondary infection related to fighting among the group-housed control animals. There was no significant difference in survival between control and exposed female mice. Under the conditions of this 2-yr study, naphthalene was not carcinogenic to male mice. In female mice it caused an increase in the incidence of pulmonary alveolar/bronchiolar adenomas. Naphthalene also caused an increase in the incidence and severity of chronic inflammation, olfactory epithelium metaplasia of hyperplasia of the nasal respiratory epithelium, and chronic nasal inflammation in the lungs of mice of each sex.