Hexachloro-1,3-butadiene (HCBD)

HCBD is not intentionally produced — it is generated as a byproduct in the manufacture of other chlorinated chemicals including carbon tetrachloride, tetrachloroethylene, trichloroethylene, and chlorine [1]. The problem is that HCBD was generated in enormous quantities during the peak years of chlorinated solvent production (1950s–1970s) and was disposed of improperly at many sites — dumped into rivers, buried in waste lagoons, or incinerated incompletely. HCBD-contaminated waste was found at multiple Superfund sites in Louisiana (where chlorinated solvent manufacturing was concentrated along the Mississippi River) and in Niagara Falls, New York, where chemical waste disposal has a long toxic history [2]. HCBD is also found in the tissues of fish from rivers receiving industrial discharge, in marine mammals globally, and in human tissue in areas with contaminated food chains [3].

Dietary exposure through contaminated fish and shellfish is the primary pathway for the general population near contaminated waterways [1]. Fish from the Mississippi River system, New Jersey coastal waters, and other areas near chemical production corridors have elevated HCBD. Groundwater contamination near Superfund sites and chemical facilities is a drinking water concern [2]. Ambient air near active production or incineration facilities contains HCBD. Occupational exposure occurs in chemical manufacturing during production of chlorinated solvents and in waste management of chlorinated byproduct streams [3].

HCBD is a probable human carcinogen (IARC Group 2B), with clear animal evidence for kidney tumors and neurotoxicity [1]. It is highly persistent in the environment (estimated half-life in soil of 3+ years) and strongly bioaccumulates in fatty tissues — its bioaccumulation factor in fish is among the highest of any chlorinated organic compound. The kidney is the primary target of toxicity in animal studies, where HCBD causes tubular necrosis and nephropathy [2]. HCBD listed under the Stockholm Convention on Persistent Organic Pollutants, reflecting global recognition of its persistence, bioaccumulation, and toxicity [3].

People who regularly eat fish from rivers and estuaries near chemical manufacturing corridors — particularly the lower Mississippi River corridor and New Jersey waterways — face dietary HCBD exposure [1]. Communities with drinking water drawn from aquifers near Superfund sites with HCBD contamination face water exposure [2]. Workers in chlorinated chemical production, particularly in distillation and byproduct management operations, have occupational exposures.

Follow state fish consumption advisories for waterways near industrial chemical production areas [1]. Test private well water if you live near a chlorinated chemical manufacturing Superfund site [2]. Reduce consumption of fatty fish from heavily industrialized waterways as a general persistent organic pollutant exposure reduction strategy [3].