Heptachlor toxicity tests

Other work has indicated that chlordane and heptachlor are energy transfer inhibitors as evidenced by marked decreases in oxidative phosphorylation of rat hepatic mitochondria following in vitro incubation of the mitochondria with the pesticides (Ogata et al. 1989). Interestingly, even though heptachlor epoxide is more toxic than either chlordane or heptachlor in tests of general toxicity, it was less effective in inhibiting mitochondrial respiration. 

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. 

In order to assess the potential extent of human exposures and health effects, members of dairy farm families who consumed raw dairy products known to be contaminated with heptachlor epoxide were studied (Stehr-Green et al. 1986). These individuals and an unexposed urban reference population were compared with regard to serum pesticide levels and liver toxicity. The farm family members had significantly higher mean serum levels of heptachlor epoxide (0.81 0.94 ppb), oxychlordane (0.70 0.75 ppb), and transnonachlor (0.79 0.60 ppb) than the unexposed population. This study is limited because exposure level, duration, and frequency of exposure are not known. There was no increase in prevalence of abnormal liver function tests in the dairy farm families... 

Death. Occupational mortality studies of pesticide workers exposed to heptachlor have not revealed an excess number of deaths in these cohorts compared to the general U.S. population. This may possibly be explained as a healthy worker effect. The ERA has described human case reports in which convulsions and death were reported following suicidal ingestion of technical-grade chlordane, which typically contains 6-30% heptachlor, but these effects cannot be attributed to heptachlor or heptachlor epoxide. There are no controlled, quantitative human data for any route of exposure. Acute lethality data were located for animals exposed via the oral and dermal routes. Both heptachlor and heptachlor epoxide may be considered very toxic via the oral route on the basis of acute animal data in rats and mice. Intermediate oral exposure to these compounds also caused up to 40% and 100% mortality in rats and mice, respectively. There appear to be differences in sensitivity in males and females in some species with the males being most sensitive. Heptachlor epoxide is more toxic than heptachlor. Heptachlor may be considered very toxic to extremely toxic via the dermal route on the basis of acute lethality data in rats and mice. The severity of acute effects may possibly depend upon the extent of formation of heptachlor epoxide and the species tested. 

EPA is currently examining the systemic and organ toxicity of heptachlor at its Health Effects Research Laboratories in Research Triangle Park, North Carolina (NTP 1990). The testing was scheduled for completion in fiscal year 1990. 

Incubations of heptachlor with a mixed culture of soil microorganisms for 12 weeks showed conversion of heptachlor to chlordene, 1-exohydroxychlordene, heptachlor epoxide, and chlordene epoxide. A mixed culture of soil microorganisms, obtained from a sandy loamy soil, degraded heptachlor epoxide to the less toxic 1-exohydroxychlordene. Conversion was about 1% per week during the 12-week test period (Miles et al. 1971). 

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