Heptachlor, toxicity

No studies were located regarding death in humans after oral exposure to heptachlor or heptachlor epoxide. However, since heptachlor is a major component of the insecticide chlordane, chlordane poisoning can be considered when evaluating heptachlor toxicity data. In the case study of a woman who ingested 6 g of chlordane with suicidal intent and died 9.5 days following ingestion, no information was presented on the composition of the chlordane. Therefore, the amount of heptachlor exposure is unknown, and the effect of other components of chlordane cannot be ruled out (Derbes et al. 1955). 

Male weanling rats were fed a 5%, 20%, or 40% casein diet for 10 days and then given heptachlor intraperitoneally. The animals receiving the 5% casein diet showed a three-fold tolerance to heptachlor toxicity, but the toxicity of heptachlor epoxide was not affected (Weatherholtz et al. 1969). This was probably due to inability of weanling rats to metabolically convert heptachlor to the more toxic heptachlor epoxide. This fact is further supported by the observation that changes in protein percentage in diet did not affect the toxicity of heptachlor epoxide itself. 

There is some evidence in laboratory animals that high-protein diets cause more rapid conversion of heptachlor to heptachlor epoxide and therefore increase the toxicity resulting from exposure to heptachlor. The lack of corroborating data in humans on this phenomenon, however, makes it difficult to postulate that high- or very high-protein diets would significantly increase susceptibility to heptachlor toxicity. 

Schimmel, S.C., Patrick, J.M., Jr., and Forester, J. Heptachlor toxicity to and uptake by several estuarine organisms, / Toxicol... 

The cyclodiene insecticides aldrin, dieldrin, endrin, heptachlor, endosulfan, and others were introduced in the early 1950s. They were used to control a variety of pests, parasites, and, in developing countries, certain vectors of disease such as the tsetse fly. However, some of them (e.g., dieldrin) combined high toxicity to vertebrates with marked persistence and were soon found to have serious side effects in the field, notably in Western European countries where they were extensively used. During the 1960s, severe restrictions were placed on cyclodienes so that few uses remained by the 1980s. 

As mentioned earlier (Figure 5.5), aldrin and heptachlor are rapidly metabolized to their respective epoxides (i.e., dieldrin and heptachlor epoxide) by most vertebrate species. These two stable toxic compounds are the most important residues of the three insecticides found in terrestrial or aquatic food chains. In soils and sediments, aldrin and heptachlor are epoxidized relatively slowly and, in contrast to the situation in biota, may reach significant levels (note, however, the difference between aldrin and dieldrin half-lives in soil shown in Table 5.8). The important point is that, after entering the food chain, they are quickly converted to their epoxides, which become the dominant residues. 

Cyclodienes A group of organochlorine (OC) insecticides, some of which are highly toxic and persistent (e.g., aldrin, dieldrin, and heptachlor). 

Narotsky MG, Weller EA, Chinchilli VM, et al. 1995. Nonadditive developmental toxicity in mixtures of trichloroethylene, di(2-ethylhexyl) phthalate, and heptachlor in a 5 x 5 x 5 design. Fund Appl Toxicol 27 203-216. 

Kearns, Weinman, and Decker rate the more common halogenated insect toxicants in the following order of decreasing toxicity (7) dieldrin, aldrin, heptachlor, 7-hexachloro-cyclohexane, chlordan, toxaphene, and DDT. This rating follows as the result of rather extensive tests on ten species of insects and is believed to represent, in general, the order of their relative activity. 

As Muller had prophesied and indeed hoped, DDT stimulated the discovery of more synthetic insecticides. DDT relatives included chlordane, toxaphene, aldrin, dieldrin, endrin, and heptachlor. Popular substitutes for DDT s family included organophosphates such as parathion, which is a powerful neurotoxin, and carbamates, which are also highly toxic to people. Unlike DDT, parathion and aldicarb have killed and injured many farm workers. Malathion was later developed to be several hundred times less toxic than parathion. 

The insecticide heptachlor oxidizes in the soil, and becomes a more toxic epoxide, capable of remaining for a long time. The insecticide aldrin transforms in the soil into dieldrin, maintaining its toxicity [15, 30]. Mirex (FDso=300-600 mg/kg), used to fight ants, just like kelevan (FDS0=255-325 mg/kg), used to fight the Colorado beetle, transform in the soil into the more toxic chlordekon (FD50 decreases to 95-140 mg/kg) [30]. 

Overall, insecticides seriously affect invertebrates in the soil, especially insects, but affect microorganisms much less [3,6]. The most toxic OCPs for soil invertebrates are heptachlor and chlordan. They sharply decrease the numbers of almost all invertebrate groups, including insects, earthworms, and ticks [6]. 

The insecticide heptachlor (FD50 for mice is 82 mg/kg [4]) oxidizes into an epoxy-product in living organisms this product is twice as toxic for practically all species [21, 35]. The insecticide aldrin (FD50 is 40-50 mg/ kg) oxidizes in plants, insects, and invertebrates, as well as in the soil it thus transforms into the seed protectant dieldrin (FD50 is 25-50 mg/kg), which is equally as dangerous to humans [15] aldrin => dieldrin. 

Chlordane-induced mortality of the long-billed curlew (Numenius americanus) has been documented at least four times since 1978, despite restriction of technical chlordane use since 1980 to subterranean applications for termite control (Blus et al. 1985). Death of these curlews was probably due to over-winter accumulations of oxychlordane of 1.5 to 5.0 mg/kg brain FW and of heptachlor epoxide at 3.4 to 8.3 mg/kg — joint lethal ranges for oxychlordane and heptachlor epoxide in experimental birds — compared to 6 mg/kg brain for oxychlordane alone and 9 mg/kg for heptachlor epoxide alone (Blus et al. 1985). Additional research is needed on toxic interactions of chlordane components with each other and with other chemicals in the same environment. 

Podowski, A.A., B.C. Baneijee, M. Feroz, M.A. Dudek, R.L. Willey, and M.A.Q. Khan. 1979. Photolysis of heptachlor and civ-chlordanc and toxicity of their photoisomers to animals. Arch. Environ. Contam. Toxicol. 8 509-518. 

Stanker LH, Watkins B, Vanderlaan M, et al. 1989. Analysis of heptachlor and related cyclodiene insecticides in food products. In Vanderlaan M, ed. ACS (American Chemical Society) Symposium Series, 451. Immunoassays for trace chemical analysis Monitoring toxic chemicals in humans, food and the environment Meeting, Honolulu, Hawaii, December 17-22. Washington, DC American Chemical Society, 108-123. 

In the case of insecticides, this oxidation converts the precursor to a product which is more toxic (e. g., the conversion of Heptachlor and Aldrin to epoxides). 

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