Heptachlor degradation

Heptachlor was a widely used pesticide, but it is now banned. It is closely related to chlordane, and like chlordane, heptachlor degrades quickly in the environment to its epoxide, in this case, called heptachlor epoxide (see below). In 1981-1987, this latter compound was a problem in milk from cows in Oahu, Hawaii, because of heptachlor contamination of pineapple greens, which had been used as cow food. 

Chemical/Physical. Slowly releases hydrogen chloride in aqueous media (Hartley and Kidd, 1987 Kollig, 1993). The hydrolysis half-lives of heptachlor in a sterile 1% etha-nol/water solution at 25°C and pH values of 4.5, 5.0, 6.0, 7.0 and 8.0 were 0.77, 0.62, 0.64, 0.64 and 0.43 weeks, respectively (Chapman and Cole, 1982). Chemical degradation of heptachlor give heptachlor epoxide (Newland et al., 1969). Heptachlor degraded in aqueous saturated calcium hypochlorite solution to 1-hydroxychlordene. Although further degradation occurred, no other metabolites were identifled (Kaneda et al., 1974). 

Results obtained by the five laboratories were reasonably consistent, and lindane recovery varied between 113 31 % and 83 25%. Heptachlor revealed poor recovery, which confirmed its degradation [339-344], The degradation product [340-342] is known to be 1-hydroxychlordene. 

Heptachlor is converted to heptachlor epoxide and other degradation products in the environment. Heptachlor epoxide degrades more slowly and, as a result, is more persistent than heptachlor. 

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). 

Production, Import/Export, Use, and Release and Disposal. Currently, heptachlor use in the United States is limited to fire ant control in power transformers (EPA 1990b). However, because of former widespread use of heptachlor and the persistence of heptachlor epoxide, these compounds and their degradation products can still be found at low levels in indoor air, water, soil, and food. Disposal methods are well documented in the literature however, more current information would be useful. Information on historical disposal practices would be helpful in evaluating the potential for environmental contamination. More information on the volume of heptachlor used in fire ant control would be useful in estimating potential occupational exposure. 

Carter FL, Stringer CA. 1970. Residues and degradation products of technical heptachlor in various soil types. J Econ Entomol 63 625-628. 

Lichtenstein EP, Schultz KR, Fuhremann TW, et al. 1970. Degradation of aldrin and heptachlor in field soils during a ten-year period translocation into crops. J Agric Food Chem 18 100-106. 

Miles JRW, Tu CM, Harris CR. 1971. Degradation of heptachlor epoxide and heptachlor by a mixed culture of soil microorganisms. J Econ Entomol 64 839-841. 

Shivankar VJ, Kavadia VS. 1989. Effects of temperature and humidity on the degradation of heptachlor residues in clay loam soil. Indian J Entomol 51(2) 205-210. 

Soil The actinomycete Nocardiopsis sp. isolated from soil extensively degraded pure cis- and /ra/3s-chlordane to dichlorochlordene, oxychlordane, heptachlor, heptachlor e/ c/o-epoxide, chlordene chlorohydrin, and 3-hydroxy-traas-chlordane. Oxychlordane slowly degraded to 1-hydroxy-2-chlorochlordene (Beeman and Matsumura, 1981). In Hudson River, NY sediments, the presence of adsorbed chlordane suggests it is very persistent in this environment (Bopp et al., 1982). The reported half-life in soil is approximately 1 yr (Hartley and Kidd, 1987). 

Heptachlor rapidly degraded when incubated with acclimated, mixed microbial cultures under aerobic conditions. After 4 wk, 95.3% of the applied dosage was removed (Leigh, 1969). In a mixed bacterial culture under aerobic conditions, heptachlor was transformed to chlordene, 1-hydroxychlordene, heptachlor epoxide, and chlordene epoxide in low yields (Miles et al, 1971). Heptachlor rapidly degraded when incubated with acclimated, mixed microbial cultures under aerobic conditions. After 4 wk, 95.3% of the applied dosage was removed (Leigh, 1969). 

White rot fungi, namely Phanerochaete chrysosporium, Pleurotus sajorcaju, Pleurotus florida, and Pleurotus eryngii, biodegraded heptachlor (50 pM) at degradation yields of 92.13 to 97.30, 59.53 to 84.76, 66.25 to 80.00, and 85.85 to 95.15%, respectively. The experiments were... 

Graham et al. (1973) reported that when solid heptachlor epoxide was exposed to July sunshine for 23.2 d, 59.3% degradation was achieved. In powdered form, however, only 5 d were required for complete degradation to occur. The products include a semicage ketone and an intermediate that may be converted to an enantiomeric semicage ketone. 

Microorganisms isolated from a loamy sand soil degraded lindane and some of the metabolites identified were pentachlorobenzene, 1,2,4,5-tetrachlorobenzene, 1,2,3,5-tetrachlorobenzene, y-PCCH, y-TCCH and p-3,4,5,6-tetrachloro-l-cyclohexane (p-TCCH) (Tu, 1976). y-PCCH was also reported as a metabolite of lindane in an Ontario soil that was pretreated with jo,//-DDT, dieldrin, lindane, and heptachlor (Yule et ah, 1967). The reported half-life in soil is 266 d (Jury et al., 1987). 

Chemical Name l,4,5,6,7,8,8-heptachloro-2,3-epoxy-3a,4,7,7a-tetrahydro-4,7-methanoindan 2,3,4,5,7,8-hexa-hydro-2, 5-methano-2//-indeno( 1,2/ )oxircnc Uses a degradation product of heptachlor CAS Registry No 1024-57-3 Molecular Formula C10H5Cl7O Molecular Weight 389.317 Melting Point (°C) ... 

Uses Heptachlor epoxide (HCE), also known as epoxyheptachlor, is a white crystalline solid. Heptachlor is converted to heptachlor epoxide and other degradation products in the environment. HCE degrades more slowly and, as a result, is more persistent than heptachlor. Both compounds adsorb strongly to sediments and are bioconcentrated in terrestrial and aquatic organisms biomagnification of both is significant.14... 

The heptachlor, dieldrin, and toxaphene examples show that foliage and soil residue dissipation data can be used to estimate the amounts of residues volatilized when no significant degradation or runoff losses are incurred. For toxaphene, residue analyses indicated that 80% of the foliage residue and 51% of the top soil residue was lost by volatilization within ca 50 days. This is considerably more than the 24% vaporization loss reported for toxaphene within 90 days in a model chamber (8), but is comparable to foliage-applied heptachlor and dieldrin (75) both of which overlap in volatility with components of the toxaphene mixture. 

Although not as well studied, nonracemic compositions of other legacy OC pesticides, as well as of a-HCH in other waters, have been observed. The Arctic Ocean was depleted in (—)-heptachlor epoxide in all regions surveyed, while cis- and tra 5-chlordane were nearly racemic [121]. Lake Ontario was also enriched in (—)-a-HCH (mean ER of 0.85), with enantiomer compositions that did not vary with depth but did vary in the presence of racemic sources such as precipitation and water from the tributary Niagara River [128]. The York River in Chesapeake Bay had microbial consortia that degraded (+)-a-HCH upstream [129, 130]. However, greater microbial activity was observed in more brackish waters... 

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