National Toxicology Program

TOX-4
Toxicity Studies of 1,2-Dichloroethane(Ethylene Dichloride) in F344/N Rats, Sprague Dawley Rats, Osborne-MendelRats, and B6C3F₁ Mice (Drinking Water and Gavage Studies) (CAS No. 107-06-2)

Chemical Formula: C₂H₄Cl₂ - 3D Structure

Thirteen-week studies were conducted to investigate potential differencesin rat strain susceptibility to 1,2-dichloroethane toxicity. F344/N rats,Sprague Dawley rats, Osborne-Mendel rats, and B6C3F₁ mice (10 animals ofeach sex) were exposed to 1,2- dichloroethane in drinking water at 0, 500,1,000, 2,000, 4,000, or 8,000 ppm for 13 weeks. In addition, Groups of 10F344/N rats of each sex were administered 1,2-dichloroethane in corn oil bygavage to compare toxicity resulting from bolus administration with that ofcontinuous exposure in drinking water. Gavage doses of 1,2-dichloroethanewere within the range of daily doses resulting from exposure in drinkingwater.

No compound-related deaths occurred in any of the rat strains exposed to1,2-dichloroethane in drinking water. Weight gain depression was common ineach sex of all three rat strains in the 4,000 and 8,000-ppm groupsthroughout the studies. Water consumption was decreased by 50%-60% withincreasing dose for all exposed male and female rats regardless of strain.Kidney and liver weights were increased in dosed rats of all three strains.No chemical-related lesions were observed except for a dose- relatedincidence of renal tubular regeneration in female F344/N rats.

Nine of 10 female mice exposed to 8,000 ppm 1,2-dichloroethane in drinkingwater died before the end of the study. Mean body weights of males at 500ppm or more and females at 1,000 ppm or more were lower than those ofcontrols throughout most of the studies. Kidney weights were significantlyincreased for dosed males and females. Renal tubular cell regeneration wasseen in males at 8,000 ppm; at 4,000 ppm, minimal regeneration was presentin 8/10 male mice.

All male F344/N rats that received 240 or 480 mg/kg and 9/10 females thatreceived 300 mg/kg 1,2-dichloroethane by gavage died before the end of thestudies. Mean body weights of the highest dose males and females were lowerthan those of vehicle controls throughout the studies. Liver and kidneyweights were increased for dosed males and females; however, nocompound-related lesions were observed. Necrosis of the cerebellum,hyperplasia, inflammation, and mineralization of the forestomach, andnecrosis of the thymus were seen in animals that died or were killed inmoribund condition.

Rat strain differences in susceptibility to 1,2-dichloroethane toxicitywere not apparent at the drinking water concentrations used in thesestudies; only female F344/N rats exhibited mild chemical related renallesions. Male B6C3FI mice appeared to be more susceptible than rats totoxicity of 1,2-dichloroethane administered in drinking water; renal tubuleregeneration was observed in male mice in the 4,000- and 8,000-ppm groups.The higher toxicity in mice was likely due to higher water consumption,resulting in up to tenfold higher doses to mice than to rats.1,2-Dichloroethane administered in drinking water resulted in less toxicityto F344/N rats than administration of similar doses by gavage.

Synonyms: Ethylene dichloride; 1,2-bichloroethane; a,ß-dichloroethane;sym-dichloroethane; ethylene chloride; glycol dichloride

Trade Names: Freon 150; Brocide; Dutch liquid; Dutch oil

Report Date: January 1991

Growth & Survival Curves for NTP 13-Week Toxicity Studies

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(NOTE: These studies were supported in part by funds from the Comprehensive EnvironmentalResponse, Compensation, and Liability Act trust fund (Superfund) by an interagencyagreement with the Agency for Toxic Substances and Disease Registry, U.S. Public HealthService.)

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