Toxicological profile of HCFC-141b (1 ,1-dichloro-1-fluoroethane)

Studies in animals indicate that dichlorofluoroethane is easily absorbed via the respiratory route.Minimal metabolism of dichlorofluoroethane to 2,2-dichloro 2-fluoroethanol occurs. This metabolite is excreted in the urine of the rat in the form of its glucuronide conjugate.

Dichlorofluoroethane has a low order of acute toxicity. No mortality was observed in rats receiving oral doses of 5,000 mg/kg; only piloerection was noted. Dermal exposure of rats or rabbits to 2,000 mg/kg caused no mortality and no signs of toxicity.

Single exposure inhalation studies in mice indicate that the LC50 (30 min) was between 300,000 and 500,000 mg/m3 (61,800 ppm and 103,000 ppm respectively) and the LC50 (4h) in rats was 300,700 mg/m3 (62,000 ppm). Six hours exposure caused narcosis in mice at 198,850 mg/m3 (41,000 ppm) and pre-narcotic signs were seen in mice and rats at levels higher than 145,500 mg/m3 (30,000ppm).

Liquid dichlorofluoroethane was not an irritant or a sensitising agent to skin, but may cause mild eye irritation.

No significant respiratory effects were seen in rats exposed to 48,500 mg/m3 (10,000 ppm) dichlorofluoroethane for 25 minutes but at this concentration cardiac sensitisation to adrenaline could be induced in dogs and monkeys.

In repeated inhalation exposure studies, rats exposed 6 h/d, 5 d/wk, during periods ranging from 2 to 13 weeks the no-effect-level was considered to be 38,400 mg/m3 (7,900 ppm). Concentration of 97,000 mg/m3 (20,000 ppm) induced reduced alertness, reduced bodyweight gain and slightly increased levels of cholesterol, triglyceride and glucose.

No haematological and histopathological changes were noted.

There was no evidence of teratogenic or embryotoxic effects in pregnant rabbits exposed to 6,790, 20,370 or 61,110 mg/m3 (1,400, 4,200 or 12,600 ppm) or in pregnant rats exposed to 15,520 or 38,800 mg/m3 (3,200 or 7,900 ppm) of dichlorofluoroethane although signs of maternal toxicity were observed at and above 15,520 mg/m3 (3,200 ppm) in rats and 20,370 mg/m3 (4,200 ppm) in rabbits.

A two "generation" inhalation study in rats demonstrated a no-observed effect level of 38,800 mg/m3 (8,000 ppm) for reproductive parameters. At a higher concentration, 97,000 mg/m3 (20,000 ppm), a "non reproducible decrease" in the number of litters, in the number of pups per litter and also some retardation of sexual maturation of male pups which may have been caused by the slight bodyweight growth retardation, was observed.

Overall dichlorofluoroethane did not present toxicologically significant genotoxic activity in vitro and in vivo.

Rats were exposed by inhalation in a lifetime study to concentrations of 7,275, 24,250 and 97,000 mg/m3 (1,500, 5,000 and 20,000 ppm). No significant evidence of toxicity was seen, however, at the highest exposure concentration reduced body weight gain was observed. Dichlorofluoroethane did not produce neoplastic changes in female rats at any test concentration. In male rats no neoplastic changes were noted at 7,275 mg/m3 (1,500 ppm) but increased incidences of testicular interstitial cell (Leydig cells) hyperplasia and adenoma were observed at 24,250 (5,000 ppm) and 97,000 mg/m3 (20,000 ppm).

These changes appeared late-in life and were not correlated with increased mortality. Because of the non-genotoxicity of dichlorofluoroethane these effects on the rat Leydig cells are considered as to be of epigenetic origin and associated with senile endocrine disturbances, and therefore of no relevance to tumourigenic hazard for man.

Joint Assessment of Commodity Chemicals No. 29
HCFC-141b (1,1-Dichloro-1-Fluoroethane)
ECETOC, december 1995