Multigeneration study of 1,2,4-trichlorobenzene in rats.

Rats were continuously exposed to 0, 25, 100, or 400 ppm 1,2,4-trichlorobenzene (TCB) in the drinking water, beginning with birth of the F0 generation and continuing through weaning of the F2 generation. The treatment did not affect fertility, growth, viability, locomotor activity, or blood chemical analysis. Adrenal gland enlargement was observed in both the F0 and F1 animals at 95 d of age. To further examine the adrenal enlargement found in the reproduction study, an acute toxicity study was undertaken in which immature females were given ip injections of 0, 250, or 500 mg/kg TCB on 3 consecutive days. It was found that TCB had no estrogenic activity and that the livers and adrenals of treated females were significantly larger than those of controls. Rather than being estrogenic, TCB in this treatment regimen resulted in a decrease in uterine weight. These two studies demonstrate that chronic or acute doses of TCB can produce adrenal enlargement in rats.