Chlordane degradation

Chlordane degrades in air by both photolysis and oxidation, trans- Chlordane photochemically degrades more readily than the cis isomer. This is indicated from the fact that the trans/cis ratio of chlordane transported long distances to the Norwegian Arctic changes from around 1 in the winter to 0.5 in the summer (Oehme 1991). Many papers have been published that detail the photoproducts of chlordane (principally cis- chlordane) and mechanisms of photoproduct formation (Feroz et al. 1981 Ivie et al. 1972 Onuska and Comba 1975 Parlar and Korte 1973, 1977, 1979,... 

In rabbits under light amytal anesthesia, chlordan has no direcr effect on the blood pressure, but produces a type of respiration having many characteristics in common with Cheyne-Stokes type. The generalized tremors, opisthotonus, tonic and clonic convulsions, produced by chlordan were decreased or abolished and respiration restored to normal by suitable injections of the sodium salts of amytal, phenobarbital, and pentothal. The LD60 of chlordan, which was about 20 mg. per kg. on intravenous administration to intact rabbits, was increased to about 60 mg. per kg. through the antidotal action of the barbiturates. An unidentified chlorine-containing degradation product with acidic properties was recovered from the urine of rabbits treated with chlordan. Approximately one third of its chlorine content was set free on hydrolysis at 100° C. with sodium hydroxide in either absolute alcohol or in water. 

The conversion in the animal body of at least some of the water-insoluble chlordan to a water-soluble degradation product must facilitate the elimination of the poison through its excretion into the urine by the kidneys. Moreover, the degradation of chlordan as shown in the present experiments may be a mechanism for its detoxification, as in the case of DDT (1). Only the isolation of the degradation product, its identification, and a study of its toxicity can determine this point. 

Biological, in four successive 7-d incubation periods, chlordane (5 and 10 mg/L) was recalcitrant to degradation in a settled domestic wastewater inoculum (Tabak et al., 1981). 

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). 

Chlordane did not degrade in settled domestic wastewater after 28 d (Tabak et al., 1981). Chlordane was metabolized by the fungus Aspergillus nigerhul it was not the main carbon source (Iyengar and Rao, 1973). 

Chlordane was widely used as a termiticide in and around homes, but it has been banned in most developed countries since about 1985. It has an environmental half-life of about 5 years. It degrades to oxychlordane (see below), which is very stable in the environment. 

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. 

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... 

As with chlordanes, toxaphene can be nonracemic in sediments, but predominantly from in situ microbial degradation. Several chlorobornane enantiomers were quantified in a 1992 sediment core from Hanson Lake, Yukon, Canada, treated with toxaphene as a piscicide in 1963 [149]. Two hexachlorinated congeners, B6-923 and an unidentified congener, were... 

The Connecticut Agricultural Experiment Station is a site of extensive experimentation on chiral chlordanes in soils and plants. An experimental plot there was sprayed with a known amount of technical chlordane in 1960, and was then covered with turf until 1998 [175]. Enrichment of (+)-c/i-chlordane and ( )-fra s -chlordane was observed [175], consistent with global trends [140]. Soils with more nonracemic m-chlordane also had more nonracemic tra i-chlordane [175], suggesting that both isomers were concurrently degraded. Crop plants planted in these soils (e.g. zucchini, cucumber, pumpkin, lettuce, spinach, pepper, tomato) depleted chlordane concentrations in the rhizosphere soils closest to the roots [176] with resulting enrichments in chlordanes in the roots [177]. This... 

Figure 4.13 Variability in enantiomer fractions (EFs) of cis-chlordane and trans-chlordane at plots In grassland (G) and woodlands (W1 and W2) In Scotland. Box plot defined as follows top and bottom of whiskers are maximum and minimum EFs, respectively top and bottom of box are 25 and 75% percentiles, respectively line in box is median EF. (Reproduced with permission from Environmental Science and Technology, Enantioselective Degradation of Organochlorine Pesticides In Background Soils Variability In Field and Laboratory Studies, by Perihan Binnur Kurt-Karakus, Jacqueline L. Stroud et af, 41(14), 4965-4971. Copyright (2007) American Chemical Society)...

Sex differences in POP toxicokinetics have also been noted. Female rats initially metabolized tra 5-chlordane to racemic oxychlordane, which later became enriched in the (—)-enantiomer post-exposure [272]. On the other hand, male rats immediately degraded tra 5-chlordane enantioselectively to (—)-oxychlordane [272]. Both sexes preferentially depleted (—)-tra s-chlordane, as well as (+)-oxychlordane in organisms individually exposed to oxychlordane, trara-chlordane, or achiral tra 5-nonachlor. These results supported the hypothesis that although CYP3A induction in rats was not sex-dependent, CYPlAl induction was [272]. More research remains to be done to elucidate the stereoselectivity of CYP induction and its effects on the metabolism of POPs. 

Li, X. Yang, L. Jans, U. Melcer, M.E. Zhang, R, Lack of enantioselective microbial degradation of chlordane in Long Island Sound sediment Environ. Sci. Technol. 2007, 41, 1635-1640. 

Pesticides are also used indoors, from which release to outdoors occurs via ventilation (see Chapter 7). Indoor use of pesticides often results in indoor air and dust concentrations 10-100 times greater than that in outdoor air and surface soil because of minimal degradation indoors. Chlordane is still released via indoor air as a result of its application to house foundations to control termites in urban areas from the 1940s to its ban in the US in 1988 and global discontinuation of production in 1997 (Leone et al, 2000 Offenberg et al, 2004). 

Leone et al. (2000) and Offenberg et al. (2004) reported racemic signatures in air concentrations of trans- and cw-chlordane in indoor air whereas samples in outdoor air and soils showed enantiomeric degradation, although Gouin et al. (2007) found that the pattern was not always consistent with the urban-rural differences. Leone et al. (2000) and Offenberg et al. (2004) concluded that indoor air was a source of chlordanes to outdoor urban air, which is similar to the conclusion reached by Robson and Harrad (2004) and Jamshidi et al. (2007) for PCBs. 

Dechlorination is a commonly occurring photochemical reaction. Organochlorine insecticides such as BHC isomers, dieldrin, heptachlor, mirex, and chlordane isomers are photo-degraded via dechlorination (Figure 11.5). 

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