Bioassay of 5-nitroacenaphthene for possible carcinogenicity (CAS No. 602-87-9).

A bioassay of 5-nitroacenaphthene for possible carcinogenicity was conducted using Fischer 344 rats and B6C3F1 mice. 5-Nitroacenaphthene was administered in the feed, at either of two concentrations, to groups of 50 male and 50 female animals of each species. For male and female rats, the high and low dietary concentrations of 5-nitroacenaphthene were 0.24 and 0.12 percent, respectively. The high and low time-weighted average concentrations for mice were 0.12 and 0.06 percent, respectively, for males and 0.12 and 0.05 percent, respectively, for females. After a 78-week dosing period, observation of surviving rats continued for up to 22 weeks and observation of the mice continued for 18 weeks. For the chronic rat bioassay, 49 male and 50 female rats were placed on test as high dose controls, and 50 rats of each sex served as low dose controls. For the mice, 50 males and 50 females were placed on test as controls. Accelerated mortality was observed in all dosed groups except the low dose female mice. There was a positive association between mortality and dietary concentration of 5-nitroacenaphthene for both sexes of both species. Early deaths were most apparent among high dose male mice; half of the animals in this group were dead by week 20 and insufficient male mice survived to be at risk from late-developing tumors. Among rats, the incidence of malignant tumors of the ear canal (incidences of ceruminous carcinomas and squamous-cell carcinomas were combined) was significant at each dose level in each sex. Among both dosed groups of female rats, the incidence of clitoral gland carcinoma and the incidence of mammary adenocarcinoma were significant. A significant incidence of alveolar/bronchiolar carcinoma was observed in low dose rat groups of each sex. Among female mice, the incidence of hepatocellular carcinoma was significant at each dose level. The combined incidence of granulosa-cell tumors, luteomas, and tubular-cell adenomas of the ovary was significant in the high dose female mouse group. Under the conditions of this bioassay, 5-nitroacenaphthene was carcinogenic to Fischer 344 rats, causing increased incidences of malignant tumors of the ear canal and lung in both sexes, and of the clitoral gland and mammary gland in females. 5-Nitroacenaphthene was also carcinogenic to female but not male B6C3F1, mice, causing carcinomas of the liver and ovarian tumors.