1,1,2,2-Tetrachloroethane

1,1,2,2-Tetrachloroethane (sym-tetrachloroethane) was one of the first synthetic chlorinated solvents, produced industrially beginning around 1905 by the chlorination of acetylene [1]. It was used widely in dry cleaning, degreasing metal parts, as an intermediate in trichloroethylene production, and as a solvent in lacquers and varnishes [2]. By the 1920s, multiple occupational fatalities and liver disease outbreaks among workers using it as an aircraft fabric stiffener and solvent prompted restrictions in many countries — it was one of the first industrial chemicals to be regulated specifically because of occupational toxicity [1]. Its use declined dramatically after the development of trichloroethylene and tetrachloroethylene as 'safer' alternatives (though these also proved to be hazardous). Today, 1,1,2,2-tetrachloroethane is found primarily as a contaminant at industrial Superfund sites where legacy chlorinated solvent contamination occurred [2].

Contaminated groundwater and soil at Superfund sites is the primary contemporary exposure pathway [1]. People drinking from private wells adjacent to former solvent-use industrial facilities, dry cleaning operations, or hazardous waste disposal sites may be exposed [2]. Trace volatilization from contaminated soil can cause indoor air exposure through vapor intrusion into buildings sited over contaminated groundwater plumes [1]. Historical occupational exposure was significant before regulatory restrictions; workers in dry cleaning, aircraft manufacturing, and metal degreasing were heavily exposed [2].

1,1,2,2-Tetrachloroethane is metabolized primarily to trichloroacetaldehyde and trichloroethanol by CYP2E1 — the same pathway as trichloroethylene [1]. The metabolic intermediates cause lipid peroxidation and centrilobular hepatic necrosis that led to the occupational fatalities in early 20th century workers [2]. In animal studies, it induced hepatocellular carcinomas. EPA classifies it as a probable (B2) human carcinogen; IARC Group 2B [1]. It is also acutely neurotoxic (headache, dizziness, narcosis) and severely hepatotoxic at occupational levels [2].

Private well users near Superfund sites with chlorinated solvent contamination [1]. Former workers in solvent, dry cleaning, and metal manufacturing industries exposed prior to regulatory restrictions [2].

1. Test your well water if near former industrial or dry cleaning sites — request tetrachloroethane analysis [1]. 2. Activated carbon filtration for contaminated water [2]. 3. Assess buildings for vapor intrusion if sited over solvent-contaminated groundwater plumes [1].