Repeated-dose and reproductive toxicity of the ultraviolet absorber 2-(3',5'-di- tert-butyl-2'-hydroxyphenyl)-5-chlorobenzotriazole in rats.

2-(3',5'-Di-tert-butyl-2'-hydroxyphenyl)-5-chlorobenzotriazole (DBHCB) is widely used as an ultraviolet (UV) absorber. In this study, the repeated dose and reproductive toxicity of DBHCB was evaluated in rats. Crj:CD(SD)IGS rats were given DBHCB by gavage at 0, 2.5, 25, or 250 mg/kg/d. Male and female rats were dosed beginning 28 d before mating, and each female rat was mated with a male rat of the same dosage group. Males were dosed for a total of 56-57 d, and females were dosed for a total of 55-69 d up to Day 3 of lactation throughout the mating and pregnancy periods. Ten males from each group were killed on the next day of the last administration, and 10 females were killed on Days 4-6 after parturition. Five rats/sex treated at 0 and 250 mg/kg/d for 56 d were then kept without treatment for 14 d (recovery period). No deaths were found in any group. No effects of DBHCB on general condition, body weight, food consumption, or reproductive/developmental parameters were observed. Significant increases in serum albumin and an albumin/globulin ratio at 25 mg/kg/d and higher and alkaline phosphatase levels at 250 mg/kg/d were noted in males. The absolute and relative weights of the liver were significantly increased in males at 25 mg/kg/d and higher. Significantly increased serum albumin and absolute and relative liver weight were also found in males at 250 mg/kg/d after the recovery period. No changes in these parameters were observed in females of any DBHCB-treated groups. No significant changes in organ histopathology were found in males or females. These findings indicated a sex difference in the toxicity of DBHCB in rats.