title: Carcinogenicity and chronic toxicity in mice and rats exposed by inhalation to para-dichlorobenzene for two years.
abstract: Carcinogenicity and chronic toxicity of para-dichlorobenzene (p-DCB) were examined by exposing 50 BDF1 mice and 50 F344 rats of both sexes by inhalation to p-DCB vapor at a target concentration of 0 (control), 20, 75 or 300 ppm for 6 hr/day, 5 days/week and 2 years. Incidences of hepatocellular carcinomas, hepatoblastomas and hepatic histiocytic sarcomas in the 300 ppm-exposed male mice, and hepatocellular adenomas and carcinomas and hepatoblastomas in the 300 ppm-exposed female mice were increased. An increase in the incidences of most of those liver tumors was dose-related. No increase in tumor incidence was found in any p-DCB-exposed rat of either sex. Centrilobular hypertrophy of hepatocytes and papillary mineralization and pelvic urothelial hyperplasia of the kidney were noted in the 300 ppm-exposed male rats. Treatment- and age-related increases in incidences of the eosinophilic globules of the respiratory and olfactory epithelia in female rats and incidences of the respiratory metaplasia of the nasal gland epithelium in mice and rats and the olfactory epithelium in mice were noted. The nasal lesion was the most sensitive endpoint of chronic inhalation toxicity. Induction of the mouse hepatocarcinogenicity and lack of the rat nephrocarcinogenicity found in the present study were compared with the mouse liver tumors and the rat renal tumors reported by the NTP gavage study, and discussed in light of the estimated p-DCB uptake into the body through the inhalation and the oral administration.
authors.affiliation: Japan Bioassay Research Center, Japan Industrial Safety and Health Association, Hadano, Kanagawa, Japan.
authors.forename: Shigetoshi
authors.initials: S
authors.lastname: Aiso
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Takeuchi
authors.forename: Heihachiro
authors.initials: H
authors.lastname: Arito
authors.forename: Kasuke
authors.initials: K
authors.lastname: Nagano
authors.forename: Seigo
authors.initials: S
authors.lastname: Yamamoto
authors.forename: Taijiro
authors.initials: T
authors.lastname: Matsushima
mesh_terms: D000280:Administration, Inhalation; D000818:Animals; D015197:Carcinogenicity Tests; D002273:Carcinogens / Q000008:administration & dosage / Q000633:toxicity*; D002722:Chlorobenzenes / Q000008:administration & dosage / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D005260:Female; D008113:Liver Neoplasms / Q000139:chemically induced* / Q000473:pathology; D008297:Male; D051379:Mice; D051381:Rats; D016019:Survival Analysis; D018675:Toxicity Tests
chemical_list: D002273:Carcinogens; D002722:Chlorobenzenes; C018511:4-dichlorobenzene