Hexachloroethane

Hexachloroethane (HCE) has an unusual production and use history compared to most industrial chlorinated solvents. Its primary application through much of the twentieth century was in military pyrotechnics — it was a key ingredient in HC (hexachloroethane/zinc oxide) smoke grenades and obscurants used by armed forces worldwide [1]. It was also used for degassing molten aluminum alloys (to remove hydrogen bubbles) and as a moth repellent and fumigant in the mid-century [2]. Industrial production as a chemical intermediate and byproduct of other chlorinated solvent manufacturing added to environmental releases. HCE is now found at many military training ranges and former metal-processing facilities. EPA classifies it as a probable human carcinogen (Group B2) and it appears on the Superfund priority pollutants list; some military smoke grenade uses continue under special circumstances while civilian uses have been sharply curtailed [1].

People living near military training ranges or former military bases where HC smoke grenades were used face soil and groundwater contamination risk [1]. Industrial sites where aluminum smelting or chlorinated chemical manufacturing occurred are secondary contamination points. Groundwater contamination can reach drinking water wells [2]. Occupational exposure historically occurred among military personnel working with smoke munitions and aluminum smelters who used HCE for degassing [1]. Because HCE is highly lipophilic and bioaccumulates, consumption of fish or game animals from contaminated areas can be a significant dietary exposure route [2].

HCE accumulates in fatty tissues and the liver, where it is metabolized by cytochrome P450 enzymes to trichloroacetyl chloride and other reactive intermediates that cause centrilobular necrosis [1]. Animal studies show liver tumors (hepatocellular carcinoma and cholangiocarcinoma) following chronic oral exposure, forming the basis for EPA's probable carcinogen classification [2]. Kidney toxicity also occurs at chronic doses. Unlike many chlorinated solvents that eventually degrade in groundwater, HCE's complete chlorination makes it resistant to reductive dechlorination under most natural conditions, so it persists at contamination sites for decades [1]. It is also immunotoxic in animal models, suppressing natural killer cell activity [2].

Residents near military ranges, former defense facilities, and aluminum smelting sites face the greatest environmental exposure [1]. Veterans who handled HC smoke grenades repeatedly over military careers had significant inhalation and dermal exposure [2]. Subsistence fishers and hunters in contaminated areas who consume high-fat tissues (fish liver, organ meats) may bioaccumulate HCE. Workers in aluminum industries who used it for degassing had direct occupational exposure [1]. Private well owners near contaminated industrial or military sites should test for HCE as part of broader chlorinated solvent screening [2].

1. If you live near a former military base or aluminum smelting facility, check EPA's Envirofacts and Superfund databases for HCE contamination and groundwater monitoring data [1]. 2. Test your well water for chlorinated solvents including HCE if you're near potential sources; activated carbon and reverse osmosis filters remove HCE effectively [2]. 3. Follow any fish consumption advisories issued by your state for lakes and rivers near military ranges or industrial sites. 4. If you are a veteran who handled HC smoke grenades, discuss your exposure history with your VA healthcare provider; Agent Orange-era and Cold War-era chemical exposures are eligible for VA evaluation [1]. 5. When buying locally hunted game near contaminated areas, avoid organ meats (liver, kidney) where HCE concentrates most highly [2].