Hexachlorocyclopentadiene

HCCP was developed in the 1940s by Shell Chemical Company as a versatile building block for chlorinated insecticides — the Diels-Alder reaction of HCCP with various dienes provides the skeleton for nearly all major cyclopentadiene-class pesticides [1]. The scale of production was enormous — hundreds of millions of pounds of HCCP were manufactured to produce the cyclodiene pesticides that dominated agricultural and termite control from the 1950s through the 1970s [2]. These pesticides — aldrin, dieldrin, endrin, chlordane, heptachlor — are now banned under the Stockholm POPs Convention due to their persistence and bioaccumulation in the food chain. HCCP itself is a dense, oily liquid with a pungent, musty odor detectable at very low concentrations. It was listed as a CERCLA hazardous substance and is found as a contaminant at former pesticide manufacturing sites [1]. Small quantities continue to be produced for specific industrial uses including flame retardants [2].

People living near former pesticide manufacturing Superfund sites (particularly in the southeastern United States where Shell and other companies operated plants) face groundwater contamination exposure [1]. HCCP is a common contaminant in the air and water near these facilities — its distinctive odor at ppb levels serves as a warning signal [2]. Occupational exposure occurred primarily in the manufacturing of cyclodiene pesticides; legacy workers face long-term cancer surveillance needs [1]. Because HCCP is the precursor to persistent pesticides, food grown in historically contaminated soils may contain trace cyclodiene residues rather than HCCP itself [2].

HCCP is acutely hepatotoxic and nephrotoxic — it inhibits mitochondrial electron transport and causes centrilobular liver necrosis [1]. It also irritates the respiratory tract severely, with animal inhalation studies showing lung damage at low concentrations [2]. HCCP is highly reactive (reacts with many nucleophiles through the electrophilic carbon centers), alkylating biological molecules. EPA classifies it as a possible human carcinogen (Group C); it induced liver tumors in animal studies [1]. Critically, HCCP is a precursor to the organochlorine pesticides (aldrin, dieldrin, chlordane) that are proven or probable carcinogens and endocrine disruptors — the population health impact of HCCP is thus multiplied through its transformation products [2].

Residents near former cyclodiene pesticide manufacturing facilities with HCCP groundwater or air contamination [1]. Former production workers at pesticide synthesis plants [2].

1. Test your well if you live near former pesticide manufacturing sites in the South and Midwest [1]. 2. Activated carbon water filtration for HCCP-contaminated water [2]. 3. Report HCCP odor (pungent, musty) from tap water or air to your local environmental agency immediately [1].