Hexachlorobenzene (HCB)

Hexachlorobenzene was used as a fungicide to protect wheat and other grain seeds from fungal damage beginning in the 1940s [1]. The Turkish poisoning outbreak of 1955–1959 was one of history's worst pesticide disasters: seed wheat treated with HCB was distributed during a severe food shortage, and hungry villagers ate it rather than plant it. Over 3,000 people developed porphyria cutanea tarda — a metabolic disease causing blistering skin, hair loss, neurological damage, and high infant mortality when mothers with the disease breastfed babies [2]. HCB use as a pesticide was banned in the US in 1965, but it persists in the environment globally as a byproduct of industrial chemical manufacturing. It is generated as an unwanted impurity in the production of pesticides, solvents, and other chlorinated chemicals, and in the incineration of municipal waste. HCB is listed among the Stockholm Convention's original 12 persistent organic pollutants — the "dirty dozen" [3].

Dietary exposure through fatty animal products is the primary ongoing pathway — HCB bioaccumulates in fatty tissues of fish, meat, poultry, and dairy [1]. Marine mammals at the top of ocean food chains have particularly high HCB levels. Background HCB is detectable in the blood and fat of most humans tested globally, reflecting decades of environmental contamination. Industrial communities near chemical manufacturing plants and waste incinerators have elevated soil and air HCB levels [2]. Breast milk transfer to nursing infants is a significant route for highly exposed mothers. People in regions where the Turkish disaster occurred still carry elevated body burdens that have been traced across generations [3].

HCB is a confirmed probable human carcinogen (IARC Group 2B) and endocrine disruptor [1]. Like other organochlorines, it accumulates in fatty tissue and disrupts multiple hormone systems. HCB strongly activates the aryl hydrocarbon receptor (AhR), the same pathway activated by dioxins and PCBs, disrupting normal development, immune function, and hormone metabolism [2]. The Turkish poisoning outbreak demonstrated the full spectrum of HCB toxicity: beyond porphyria (a severe metabolic disease where heme production is disrupted), victims developed skin hyperpigmentation, weakness, joint disease, and neurological damage. Infant mortality was extremely high for babies breastfed by poisoned mothers — up to 95% mortality in heavily exposed infants [3].

People who eat fatty ocean fish, marine mammals, or large quantities of animal fats from industrially contaminated regions carry higher HCB body burdens [1]. Industrial workers in chlorinated chemical production and waste incineration face occupational inhalation exposures. People living near former agricultural chemical production facilities, waste incinerators, and industrial chlorination plants may face elevated environmental exposures [2]. Nursing infants of mothers with high HCB body burdens receive concentrated exposure through breast milk.

Reduce consumption of high-fat animal products, especially fatty ocean fish and marine mammals from polluted regions [1]. Choose diverse food sources from multiple geographic origins to average out regional contamination. Follow state fish consumption advisories for your region [2]. Industrial workers should use NIOSH-approved respiratory protection when working with processes that may generate HCB as a byproduct, and should request biomonitoring (blood or fat HCB measurements) if they suspect significant exposure [3].