Mirex, structure

Moser GJ, Robinette CL, Smart RC. 1993. Characterization of skin tumor promotion by mirex structure-activity relationships, sexual dimorphism and presence of Ha-ras mutation. Carcinogenesis 14(6) 1155-1160. 

Widespread use of mirex may lead to altered population structure in terrestrial systems, with resurgence or escalation of nontarget pests due to selective mirex-induced mortality of predators (NAS 1978). For example, populations of immature horn flies and rove beetles, two species of arthropods normally preyed upon by fire ants, were higher in mirex-treated areas than in control areas (Howard and Oliver 1978). Conversely, other species, such as crickets, ground beetles, and various species of oil-loving ants, were directly affected and populations were still depressed or eliminated 14 months posttreatment (NAS 1978), whereas fire ants recovered to higher than pretreatment levels, as judged by mound numbers and mound size (Summerlin et al. 1977). 

Mirex and chlordecone are two separate synthetic insecticides that have similar chemical structures. They do not occur naturally in the environment. Mirex is a snow-white crystalline solid and chlordecone is a tan-white crystalline solid. Both compounds are odorless and neither burns easily. 

Mirex and chlordecone are structurally similar insecticides. The only structural difference is that mirex has two bridgehead chlorine atoms where chlordecone has a carbonyl oxygen atom. As suggested by this similarity in structure, these two chemicals produce similar toxicities in a number of organs. Flowever, several aspects of the toxicity of mirex are distinctly different from those of chlordecone, and vice versa. Because the toxicity profiles of mirex and chlordecone differ significantly, each chemical will be discussed separately below. 

Hepatic Effects. Hepatic changes were observed in one chronic human exposure to mirex, as well as in a number of workers exposed to chlordecone for intermediate or chronic durations. In the mirex study, human subjects (sex and number not specified) from a chronically exposed cohort from southeast Ohio (route of exposure not specified, assumed to be oral) were assessed for cytochrome P- 4501A2 induction using a breath test that measures caffeine metabolism. The subjects exposed to mirex had elevated caffeine metabolism as compared to negative control individuals (subjects with no known exposure to polyhalogenated biphenyls or other related chemicals) in which the metabolism did not increase (Lambert et al. 1992). In the chlordecone study, liver function and structure in 32 men exposed to high levels of chlordecone while employed for 1-22 months (5.6... 

A second study examined the effects of DMBA initiated mi rex-promoted tumors in female mice on ovarian hormones. This study found that the loss of ovary (OVX) protected the female mice (40%) from mirex tumor promotion. Tumor promotion was unaffected in DMBA-initiated OVX mice promoted with TPA. Based on the data, the authors also concluded that there is a structural specificity in the tumor-promoting ability of mirex in mouse skin and that mirex is a much more effective skin tumor promoter in female CD-1 mice than in male CD-1 mice or OVX mice (Meyer et al. 1994). 

Although mirex and chlordecone are structurally very similar (differing only in the replacement of two bridgehead chlorine atoms on the mirex molecule with a carbonyl oxygen on the chlordecone molecule), significant differences exist in the toxicity profiles of these two chemicals. Therefore, mirex and chlordecone will be discussed separately below. 

Chlordecone is similar to mirex in structure and is also highly persistent in soils and sediments (halflife expected to be analogous to 10 years duration for mirex) because of its resistance to biodegradation, although some microbial metabolism of chlordecone has been reported (Lai and Saxena 1982 Ordorff and Colwell 1980). No evidence of microbial degradation was detected for chlordecone exposed to hydrosoils from a reservoir (not previously contaminated with chlordecone) and from Bailey Creek (contaminated with chlordecone) under either anaerobic or aerobic conditions for 56 days (Huckins et al. 1982). 

Mirex 2385-85-5 1958 20-30% of mirex for termite control in structures of houses, dams and underground cable boxes. 1997 Same as above... 

Chlordecone (Kepone) Mirex is structurally similar with 2 Cls in place of =0... 

Organochlorine insecticides may be divided into three broad groups dichlorodiphenylethanes, such as DDT and methoxychlor cyclodienes, such as chlor-dane and dieldrin and hexachlorocyclohexanes, such as lindane. Mirex and chlordecone, however, are organochlorine insecticides whose caged structures do not fit well into the previous groups. 

Fig. 2 Molecular structures of the Dirty Dozen. 1 - Polychlorinated dibenzo-p-dioxines, PCDD 2 - Polychlorinated dibenzofuranes, PCDF 3 - Polychlorinated biphenyls, PCB 4 - Hexachlorobenzene, HCB 5 - 2,2-Bis(4-chlorophenyl)-l,l,l-trichloroethane, DDT 6 - Toxaphene 7 - Aldrin 8 - Dieldrin 9 - Endrin 10 -Chlordane 11 - Heptachlor 12 - Mirex.

The remarkably amplified lethality (Table IX 2,10, 137-141) is unprecedented. The highly unusual aspect of the interaction is that mirex, a closely related structural analog does not potentiate haloalkane hepatotoxlclty with nearly the propensity... 

Because the life cycles of insects are short, they can evolve an immunity to insecticides within a short period. As early as 1948, several strains of DDT-resisfant insects were identified. Today, fhe malaria-bearing mosquitoes are almosf completely resistant to DDT, an ironic development. Other chlorocarbon insecticides were developed to use as alternatives to DDT against resistant insects. Examples of fhese chlorocarbon materials include Dieldrin, Aldrin, Chlordane, and the substances whose structures are shown here. Heptachlor and Mirex are prepared using Diels-Alder reactions. 

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