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The toxicologic and carcinogenic potential of naphthalene was studied by exposing groups of male and female B 6 U F , mice to atmospheres containing 0 (7.5 mice per sex), 70 ppm (7.5 mice per sex), or 30 ppm (150 mice per sex) of the chemical for 6 h daily, 5 dayslwk for 703 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.A complete account for this study was presented in National Toxicology Program Technical Report 410 entitled "Toxicology and Carcinogenesis Studies of Naphthalene." 393 Inhalation Toxicology, 4993409,1992 Copyright 0 1992 by Hemisphere Publishing Corporation Inhalation Toxicology Downloaded from informahealthcare.com by McMaster University on 02/20/15 For personal use only. 394 K. M. ABDO ET AL.

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Strain A/J mice were exposed by inhalation for 6 h/d, 5 d/wk, for 6 mo to carbon disulfide, 1,2-dibromoethane, ethylene oxide, naphthalene, nitrogen dioxide, or vinyl chloride. Significant increases in pulmonary adenoma formation were observed following exposure to 300 ppm carbon disulfide; 20 and 50 ppm 1,2-dibromoethane; 70 and 200 ppm ethylene oxide; 10 ppm nitrogen dioxide; and 50, 200, and 500 ppm vinyl chloride compared to control animals. Repeated studies with 1,2-dibromoethane, ethylene oxide, and vinyl chloride gave similarly significant results. Exposure of mice to 30 ppm naphthalene did not elicit a significant adenoma response. Histopathological examination of lungs from animals in these studies revealed multiple alveolar adenomas. Results from earlier studies with these chemicals, using strain A mice and Swiss mice, and bioassay information with rats and mice were compared with these data. These results provide further information for the validation of this in vivo model as a tool for predicting oncogenic potential following chemical exposure.