Insecticides Heptachlor

Gomez-Arroyo S, Baiza AM, Lopez G, et al. 1985. A comparative study of the cytogenetic effects of the insecticides heptachlor, malathion, and methyl parathion in Vicia faba. Contaminacion Ambiental 1 7-16. 

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]. 

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. 

Osetrov V.I. Materialy po toksikologicheskomu i gigienicheskomu normirovaniyu novogo insektitsida geptakhlora (Materials on the Toxicological, and Health Standards of the New Insecticide Heptachlor) Dis.. ..Candidate of Medical Sciences. Kiev, 1959. 184 pp. 

Mestitzova M. 1967. On reproduction studies and the occurrence of cataracts in rats after long-term feeding of the insecticide heptachlor. Experientia 23 42-43. 

Heptachlor was in extensive use until the 1970s for the control of certain soil-inhabiting insects that attack com and other field crops, cotton insects, grasshoppers, and for the treatment of crop seeds. Along with other cyclodiene insecticides, heptachlor is uniquely suited for termite control. Since 1988, it has not been used for the control of termites, but it is permitted for commercial use in the United States for fire ant control in power transformers.24 Nonachlor is a by-product created during the manufacture of chlordane and heptachlor. 

As with other cyclodiene insecticides, heptachlor blocks the neuronal uptake of chloride ions by blocking the activity of y-aminobutyric acid. This results in only a partial repolarization of activated neurons leading to an uncontrolled excited condition. Additionally, chlordane inhibits Ca, Mg -adenosine triphosphatase (ATPase) and Na,K-ATPase functions, leading to increased concentrations of... 

As with most organochlorine insecticides, heptachlor and its epoxide are highly persistent in soils, with a reported representative field half-life of 250 days. Heptachlor and its epoxide are moderately bound to soils. This should significantly limit their mobility. Due to their persistence, even low mobility may result in appreciable movement. Therefore, heptachlor and heptachlor epoxide may pose a risk of groundwater contamination over time. Heptachlor epoxide exhibits a low susceptibility to biodegradation, photolysis, oxidation, or hydrolysis in the environment. 

The Association of Official Analytical Chemists recommends a Volhard titration for analysis of the insecticide heptachlor, C10H5CI7. The percentage of heptachlor is given by... 

Chuang LF, Liu Y, Killam K Jr, et al. 1992. Modulation by the insecticides heptachlor and chlordane of the cell-mediated immune proliferative responses of rhesus monkeys. In Vivo 6 29-32. 

Cyclodienes. These are polychlorinated cycHc hydrocarbons with endomethylene-bridged stmctures, prepared by the Diels-Alder diene reaction. The development of these insecticides resulted from the discovery in 1945 of chlordane, the chlorinated adduct of hexachlorocyclopentadiene and cyclopentadiene (qv). The addition of two Cl atoms across the double bond of the ftve-membered ring forms the two isomers of chlordane [12789-03-6] or l,2,4,5,6,7,8,8-octachloro-2,3,3t ,4,7,7t -hexahydro-4,7-methano-lJT-indene, QL-trans (mp 106.5°C) and pt-tis (32) (mp 104.5°C). The p-isomerhas signiftcantiy greater insecticidal activity. Technical chlordane is an amber Hquid (bp 175°C/267 Pa, vp 1.3 mPa at 25°C) which is soluble in water to about 9 fig/L. It has rat LD qS of 335, 430 (oral) and 840, 690 (dermal) mg/kg. Technical chlordane contains about 60% of the isomers and 10—20% of heptachlor. It has been used extensively as a soil insecticide for termite control and as a household insecticide. 

The com rootworms Diabrotica barberi and D. virgijera were controUed in the U.S. com belt from 1954 to 1964 by soil appHcations of heptachlor and aldrin. A resistant race of the western com rootworm D. virgijera was first characterized in southeastern Nebraska in 1961 and spread rapidly throughout the entire com belt. Successive introductions of carbamate and organophosphate soil insecticides have increased the cost of com rootworm control from... 

Lindane is one of eight different hexachlorocyclohexane (HCH), C H Cl, isomers and its Chemical Abstract n.2cniQ is la, 2a 3P, 4a, 5a 6P-hexachlorocyclohexane [58-89-9] (y-HCH or y-BHC, ben2ene hexachloride) (80). Commercial products containing lindane are marketed as either a mixture of isomers or as the pure y-BHC isomer. Not unexpectedly, lindane is a highly stable lipophilic compound and it has been used extensively worldwide as an insecticide. In contrast, hexachloropentadiene, C Cl, is an extremely reactive industrial intermediate used as a chemical intermediate in the synthesis of a broad range of cyclodiene-derived pesticides, which include endosulfan, endrin, heptachlor, and several different organohalogen flame retardants (81). 

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. 

In one example (Lawrence and Casida 1984, Abalis et al. 1985) rat brain microsacs were used to test the action of cyclodiene insecticides such as dieldrin and endrin on the GABA receptors contained therein. The influx of radiolabeled CL into the microsacs via the pore channel of the receptor was inhibited by these chemicals. A similar assay was developed using microsacs from cockroach nerve. Assays with this preparation showed again the inhibitory effect of a cyclodiene (this time heptachlor epoxide) on CL influx. Also, that microsacs from cyclodiene resistant cockroaches were insensitive to the inhibitory effect of picrotoxinin, which binds to the same site on the GABA receptor (Kadous et al. 1983). 

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

L.H. Stanker, B. Watkins, M. Vanderlaan, R. Elhs, and J. Rajan, Analysis of heptachlor and related cyclodiene insecticides on food products, in Immunoassays for Trace Chemical Analysis, ed. M. Vanderlaan, L.H. Stanker, B.S. Watkins, and D.W. Roberts, American Chemical Society, Washington, DC, Chapter 12, pp. 108-123 (1991). 

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. 

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]. 

Aspila et al. [338] reported the results of an interlaboratory quality control study in five laboratories on the electron capture gas chromatographic determination of ten chlorinated insecticides in standards and spiked and unspiked seawater samples (lindane, heptachlor, aldrin, 5-chlordane, a-chlordane, dield-rin, endrin, p, p -DDT, methoxychlor, and mirex). The methods of analyses used by these workers were not discussed, although it is mentioned that the methods were quite similar to those described in the water quality Branch Analytical Methods Manual [339]. Both hexane and benzene were used for the initial extraction of the water samples. 

A second organochlorine pesticide, heptachlor (HEP), a chlorinated cyclodiene that was used primarily as an agricultural and domestic insecticide, was evaluated for its potential to suppress the immune system of rats. Rats were exposed to HEP pre-and postnatally, as described above for MXC. The IgM antibody response to SRBCs was suppressed at all doses in males but not females at 8 weeks of age. At 26 weeks of age, the IgG anti-SRBC response was suppressed in all of the HEP-exposed males, but not females.131... 

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