beta-Hexachlorocyclohexane (alias of Beta-Hexachlorocyclohexane)

CAS RN:319-85-7

Toxicity Summary

IDENTIFICATION AND USE: Beta-hexachlorocyclohexane(beta-HCH) is a colorless, sand-like powder. It is a component of technical grade HCH. HUMAN EXPOSURE AND TOXICITY: The chronic toxicity for isomers of HCH decreases in the order beta > alpha > gamma > delta and is directly related to their tissue retention, and inversely to rates of metabolism. This contrasts with the order of acute toxicities, which are in the decreasing order of gamma > alpha > delta > beta. The beta HCH isomer causes central nervous system depression. One case report of a Japanese sanitation employee with acute leukemia was associated with occupational exposure to HCH and DDT. ANIMAL STUDIES: Symptoms of poisoning in rats were decreased activity, ataxia, tremors, dyspnea, anorexia, convulsions, and rough fur. Beta-HCH was shown to be uterotrophic in ovariectomized adult mice following 3 daily doses, and sufficient levels had been stored in body tissues such that a 2-day fast 14 days after the beta-HCH exposure also increased water inhibition by the uterus. When young male rats were administered 800 mg beta-HCH/kg diet for 2 weeks, liver weight was increased but no differences in the content of water, nitrogen, protein, or glycogen were found. Liver fat content was increased and the DNA content per kg tissue was decreased, but the whole liver DNA content was increased. The most predominant change in the liver was hypertrophy of the liver cells. The testes weight was not different from that of the control animals but the protein content was higher. The testicular DNA content was lower than in control animals. The histological changes reported were testicular tubular atrophy, interstitial edema, and spermatogenic arrest. Increases in benign liver tumors in mice fed beta-HCH. In addition, beta-HCH is a tumor promotor in rats. The tumor-promoting action was generally associated with liver growth and induction of monooxygenases or other specific enzymes. Mice treated with 57 or 190 mg/kg/day beta-HCH for 30 days developed ataxia within 1 week of treatment. A significant delay in tail nerve conduction velocity was reported in rats fed 66.3 mg beta-HCH/kg/day for 30 days. In rats brain levels of 4-5 mg beta-HCH/kg had an anti-convulsive effect. Neurotoxic effects (ataxia and adynamia) occurred at brain levels of 15-20 mg beta-HCH/kg. Beta-HCH did not induce mutations in Salmonella typhimurium strains TA 98, TA 100, TA 1535, or TA 1537. Chromosome breaks and gaps were observed in metaphase preparation of bone-marrow cells from rats injected with beta-HCH. ECOTOXICITY STUDIES: beta-HCH exerts an estrogenic action on male and female guppies at 0.1 mg/L and higher, which is analogous to the effect reported in rodents. In medaka, Oryzias latipe after 1 and 3 months histopathological examinations revealed development of hermaphroditism in males and induction of vitellogenesis in either sex after 3 months. These features are characteristic of estrogen like activity.
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