Toxaphene

Toxaphene is a complex mixture of over 670 chlorinated camphene compounds produced by chlorinating camphene, a natural terpene [1]. It became commercially available in 1947 and rapidly became one of the most widely used insecticides in the US cotton belt, with annual application exceeding 60 million pounds at its peak. It was preferred over DDT for some crops because it had lower mammalian toxicity and was effective against a broader range of pests [2]. The EPA began restricting toxaphene in 1982 and completed the ban in 1990, primarily because of its extreme persistence and bioaccumulation in the Great Lakes fish food chain. Lake Superior fish (lake trout, lake whitefish) had among the highest toxaphene concentrations of any US fish, requiring strict consumption advisories [3]. Toxaphene is now a Stockholm Convention persistent organic pollutant.

Dietary exposure from Great Lakes fish and from fish in areas with historical heavy cotton belt use is the primary ongoing pathway for most Americans [1]. Toxaphene bioaccumulates dramatically in fatty fish — Great Lakes fish in the 1980s and 1990s had toxaphene at levels hundreds of times higher than surrounding water. Even now, decades after the ban, residues persist in Great Lakes sediment and fish [2]. Residents of former cotton-growing areas in the South may have soil exposure. People who consumed large quantities of Great Lakes fish prior to the ban accumulated significant body burdens [3].

Toxaphene is classified as a probable human carcinogen (IARC Group 2B), primarily based on animal evidence for liver cancer and thyroid tumors [1]. As a persistent organochlorine mixture, toxaphene accumulates in fatty tissues and is extremely slowly metabolized. The individual components of the mixture have varying toxicities — some components are more estrogenic, some more androgenic, and some more neurotoxic — making toxaphene risk assessment particularly complex [2]. Thyroid effects have been documented in animal studies, and some human studies suggest associations between organochlorine body burden (including toxaphene) and thyroid function alterations [3].

People who regularly consumed Great Lakes fish (lake trout, lake whitefish, salmon) from the 1970s through 1990s carry significant toxaphene body burdens [1]. Residents of former cotton-growing areas in the South with private wells and vegetable gardens on historically treated land may have soil and water exposure. Indigenous communities that subsist on Great Lakes fish are among the most affected populations [2].

Follow Great Lakes fish consumption advisories, which remain relevant for toxaphene and multiple other persistent organic pollutants decades after the ban [1]. Trim fat from Great Lakes fish and avoid cooking in drippings to minimize toxaphene consumption from fish that fall below consumption advisory thresholds [2]. Choose diverse seafood sources including ocean fish from less-contaminated regions [3].