Prechronic toxicity of o-benzyl-p-chlorophenol in rats and mice.

o-Benzyl-p-chlorophenol (BCP) is a major household and industrial germicide. Its prechronic toxicity was evaluated in male and female F344 rats and B6C3F1 mice. Treatment was by gavage in corn oil. BCP was slightly toxic after acute oral exposure, with high mortality at 4000 and 2000 mg/kg in rats and mice. Exposure to 12 oral doses of BCP at 1000, 500, 250, 125, 62.5, or 0 mg/kg body wt resulted in dose-related cecal dilatation and nephrosis in both rats and mice. Doses for the subchronic studies were based on the results of the 2-week studies. Ten animals were treated per dose per sex. Rats received 480, 240, 120, 60, 30, or 0 mg BCP/kg. Mice were treated with 1000, 800, 650, 500, or 0 mg BCP/kg. Animals were dosed 5 days per week for 13 weeks. Clinical signs related to dosing included urogenital staining in rats and rough/oily haircoats in mice. No effects on growth rate were seen in rats, but growth was retarded at the higher doses used in mice. Kidney weights increased in rats, and liver weights increased in mice. A decrease in thymus weight accompanied by a depletion in thymic lymphocytes (rats) or thymic necrosis (mice) occurred only in a high-dose animals. In both species, the kidney was the major target organ. In rats, there was an increase in incidence and severity of nephropathy and renal tubule regeneration. The lesions in mice primarily involved the renal cortex and included necrosis, casts, chronic inflammation, and regeneration of the renal tubules. No effects of BCP exposure in rats were seen in a broad spectrum of hematology or urinalysis parameters. Minor decreases in blood urea nitrogen, creatinine, and alanine amino transferase were detected in male and female rats. There were no biologically significant neurobehavioral effects in rats or immunotoxic effects in mice due to exposure to BCP. Thus, the kidney is the major target organ for BCP.