A review of whole animal bioassays of the carcinogenic potential of naphthalene

• Published in: Regulatory toxicology and pharmacology Vol. 51; no. 2; pp. 6 - 14
• Main Authors: North, D. Warner, Abdo, Kamal M., Benson, Janet M., Dahl, Alan R., Morris, John B., Renne, Roger, Witschi, Hanspeter
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Inc 01.07.2008
• Subjects: Adenoma - chemically induced; Adenoma - pathology; Administration, Inhalation; Animal bioassay; Animals; Bronchi - drug effects; Bronchi - pathology; Cancer; Carcinogenesis; Carcinogenicity Tests - methods; Carcinogens, Environmental - administration & dosage; Carcinogens, Environmental - classification; Carcinogens, Environmental - toxicity; Cytotoxicity; Esthesioneuroblastoma, Olfactory - chemically induced; Esthesioneuroblastoma, Olfactory - pathology; Female; Inhalation Exposure; Inhalation studies; Lung Neoplasms - chemically induced; Lung Neoplasms - pathology; Male; Maximum tolerated dose (MTD); Mice; Naphthalene; Naphthalenes - administration & dosage; Naphthalenes - classification; Naphthalenes - toxicity; Nasal Cavity - drug effects; Nasal Cavity - pathology; National Toxicology Program (NTP); Nose Neoplasms - chemically induced; Nose Neoplasms - pathology; Olfactory Mucosa - drug effects; Olfactory Mucosa - pathology; Pulmonary Alveoli - drug effects; Pulmonary Alveoli - pathology; Rats; Tumorigenesis; National Toxicology Program (NTP); Naphthalene; Animal bioassay; Cytotoxicity; Tumorigenesis; Inhalation studies; Carcinogenesis; Cancer; Maximum tolerated dose (MTD)
• ISSN: 0273-2300; 1096-0295
• DOI: 10.1016/j.yrtph.2007.09.022

This report provides a summary of deliberations conducted under the charge for members of Module A participating in the Naphthalene State-of-the-Science Symposium (NS3), Monterey, CA, October 9–12, 2006. Whole animal bioassays have been performed by the National Toxicology Program in mice and rats to ascertain the carcinogenic potential of naphthalene by inhalation exposure. A statistically significant increased incidence of pulmonary alveolar/bronchiolar adenoma (a benign lesion), was observed among female mice; an observed increase among the males did not reach statistical significance. No nasal tumors were observed in either sex. A tumorigenic response was observed in both sexes of rats, in males an increased incidence of nasal respiratory epithelium adenoma (a benign rather than malignant lesion) and in females, olfactory epithelial neuroblastoma. Interpretations of these studies vary. On the one hand, evidence of extensive non-neoplastic response in both sexes of both species indicates cytotoxicity occurred at all doses, and strongly suggests that cytotoxicity played a significant role in the tumor responses observed in the target tissues. On the other hand, olfactory epithelial neuroblastoma has rarely been observed in NTP bioassays. This review seeks to develop a consensus understanding of the scientific evidence provided by these studies, taking into account that they have been used as the basis for quantitative human cancer risk assessment, and suggests scientific studies that, if performed, could resolve scientific uncertainties.