Pesticides, chlorinated Heptachlor

A variety of methods has been devised for the confirmation of heptachlor residues (Table II). The presence in the heptachlor molecule (Figure 1) of a reactive allylic chlorine atom has been the basis of three confirmatory tests based on its ease of replacement. Reaction with a silver acetate-glacial acetic acid mixture produced 1-acetoxychlordene which, with the GLC conditions used, had a retention time close to heptachlor epoxide 44). Of the common organochlorine pesticides, only heptachlor reacted quantitatively. Endrin reacts to a small extent with the glacial acetic acid to give a secondary endrin ketone peak. When the reaction of heptachlor with silver salts was extended to silver carbonate in aqueous alcohol, 1-hydroxychlordene was obtained which can easily be converted to the more volatile and GG-responsive silyl ether. Unfortunately, this silyl ether has a Rt identical to aldrin. With silver carbonate, hepta-... 

Polychlorinated Pesticides. A once substantial but now diminished use for DCPD is in the preparation of chlorinated derivatives for further use or synthesis into pesticide compounds (see Insectcontrol technology). Soil permanence and solubiUty of the products in human fatty tissues have considerably restricted the use of these compounds. The more prominent chlorinated pesticides were aldrin, dieldrin, chlordane, and heptachlor, all of which use hexachorocyclopentadiene as a starting material. Aldrin and dieldrin are no longer used in the U.S. Chlordane and heptachlor are stiU produced, but only for export use. 

Most of the common 15 hazardous pesticides are chlorinated hydrocarbons. Adsorption can be an important process for most. All except DDT, endosulfan, and heptachlor resist hydrolysis, and most are also resistant to biodegradation. Kearney and Kaufman118 review conditions under which chlorinated pesticides are biodegraded. 

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... 

Rachel Carson s book Silent Spring that was published in 1962, was the first popular work to bring the uncontrolled environmental contamination by pesticides to public attention. Well-publicized and well-organized campaigns were mounted in several countries to prohibit the use of DDT and other persistent chlorinated insecticides such as Aldrin and heptachlor. Governments in many developed countries like USA,... 

Terrence Collins is the Thomas Lord Professor of Chemistry at Carnegie Mellon University who contends that the dangers of chlorine chemistry are not adequately addressed by either academe or industry, and alternatives to chlorine and chlorine processors must be pursued. He notes, Many serious pollution episodes are attributable to chlorine products and processes. This information also belongs in chemistry courses to help avoid related mistakes. Examples include dioxin-contaminated 2,4,5-T, extensively used as a peacetime herbicide and as a component of the Vietnam War s agent orange chlorofluorocarbons (CFCs) polychlorinated biphenyls (PCBs the pesticides aldrin, chlordane, dieldrin, DDT, endrin, heptachlor, hexachlorobenzene, lindane, mirex, and toxaphene pentachlorophe-... 

Estimated half-lives for chlorinated hydrocarbon pesticides vary widely [16, 22] Aldrin, 1-9 Dieldrin, 3-7 Chlordane, 1-8 Heptachlor, 1-4 and DDT, 3-10 years. Half-lives for PCBs range from one year to 16 years [23]. Other types of pesticides, e.g. organophosphates, triazines, carbamates and ureas, are generally less persistent [16, 24],... 

The inclusion of a third-order term did not yield a significantly better fit (p > 0.6). There are no indications that PAHs and nonpolar chlorinated hydrocarbons have a different Ks - Ko dependence. By contrast, the moderately polar pesticides such as hexachlorocyclohexanes (HCHs), dieldrin, chlorpyrifos, heptachlor, and trifluralin (open and closed diamonds in Figure 3.3) have Ks values that are 0.6 log units lower than PAHs and PCBs with similar Ko values (p < 0.001). 

Below-grade bioremediation is an ex situ technology designed to treat soil, sludge, and sediment impacted with chlorinated cyclodiene insecticides such as chlordane and heptachlor. Naturally occurring fungi are added to pesticide-contaminated soil, which is then treated in a below-grade actively aerated bioremediation cell. 

Organic compounds, aromatic solvents (benzene, toluene, nitrobenzenes, and xylene), chlorinated aromatics (PCBs, chlorobenzenes, chloronaphthalene, endrin, and toxaphene), phenols and chlorophenols (cresol, resorcinol, and nitrophe-nols), polynuclear aromatics (acenaphthene, benzopyrenes, naphthalene, and biphenyl), pesticides and herbicides (DDT, aldrin, chlordane, BHCs, heptachlor, carbofuran, atrazine, simazine, alachlor, and aldicarb), chlorinated... 

Chlordane is a mixture of at least 120 compounds and technical chlordane typically contains 64-67% chlorine (Dearth Hites, 1991a,b WHO, 1995). Of these 120 compounds, 60-75% are chlordane isomers (cis- and irons- ) and the remainder is related to endo-compounds that include heptachlor, nonachlor, diels-alder adduct of cyclopentadiene and penta/hexa/octachlorocyclopentadienes (UNEP Chemicals, 2002). Heptachlor contributes up to 10% of technical chlordane and it is also a pesticide formulation. 

The American Public Health Association [97,98] published an early gas chromatographic method for the solvent extraction and gas chromatographic determination of 11 chlorinated insecticides in water samples in amounts, down to 0.005mg L 1 p,p -DT)E, p,p -DDT, Aldrin, Dieldrin, Endrin, Heptachlor, Heptachlor epoxide, Lindane, Isodrin and Methoxychlor. The insecticides Carbophenothion, Chlordane, Dioxathion, Diazinon, Ethion, Malathion, Parathion methyl, methyl Trithion, Parathion, Toxaphene and VC-13 may be determined when present at higher levels. Also, the chemicals chlordane, hexachlorobicycloheptadiene and hexachlorocyclopentadiene, which are pesticide manufacturing precursors, may be analysed by this method. 

Cyclodienes are an important group of chlorinated pesticides. The group hep-tachlor includes insecticides such as chlordane, aldrin, dieldrin, endosulfan, and heptachlor and its epoxide. These are used for the control of a variety of plant pests in agriculture and household environments. The entry of cyclodienes to the global market has created easy management for the control of crop pests. They appeared after World War II as tools to protect food crops and control diseases from pests. In fact, humans were protected from malaria, typhus, and loss of food crops by pesticides. 

Pesticides Carbamate insecticides and herbicides, chlorinated pesticides (for example aldrin, dieldrin, heptachlor, DDT, DDE, HCB, HCH isomers), dithiocarbamate fungicides, organic phosphates, triazine herbicides... 

DDT is not the only chlorinated hydrocarbon used as a pesticide. Other compounds in this class include dieldrin, aldrin, heptachlor, and chlordan. The use of these compounds has also been banned or restricted in the United States. The U.S. government has decided the harm they cause to the environment is more important than the benefits they provide to farmers and other users. 

A large number of ubiquitous environmental pollutants are very toxic to the hypothalamic-pituitary-thyroid (HPT) axis when administered at high (greater than environmental) levels. To study low level effects on the HPT axis, laboratory animals were administered a mixture of 16 organochlorine pesticides and other chlorinated hydrocarbons and heavy metals, all at levels similar to those found environmentally, so as to simulate environmental exposure. The chemicals included DDT (6.91), HCB (5.73), TCDD (6.80), PCBs (6.29), methoxychlor (5.08), endosulfan (3.83), heptachlor (6.10), hexachlorocyclohexane (3.80), dieldrin (5.40), aldrin (6.50), mirex (7.18), several chlorinated benzenes (2.84-3.44), cadmium (-1.65), and lead (1.35). Effects were measured by monitoring thyroid activity. The study found that this mixture of environmental pollutants was toxic and can alter HPT physiology in sexually mature malesJ50 ... 

Of the several classes of synthetic insecticides, the chlorinated hydrocarbon (CH) and organophosphate (OP) insecticides have the greatest psychiatric significance [Pesticides and Neurological Diseases 1982 Ecobichon 1996). The CH insecticides, also called organochlorine insecticides, include three chemical classes di-chlorodiphenyltrichloroethane (DDT), cyclodienes (aldrin, dieldrin, heptachlor, chlordane, endosulfan), and chlorinated benzene and cyclohexanes (lindane) (Ecobichon 1996). Their ban in the United States and Europe resulted from their high chemical stability and lipid solubility that allowed environmental persistence and magnification in the food chain (Ecobichon 1996 Kaloyanova and El Batawi 1991). 

Biotransformation of certain chlorinated hydrocarbon insecticides results in their conversion to metabolites which are less polar than the parent chemical. Heptachlor and aldrin are converted to the more lipophilic compounds heptachlor epoxide and dieldrin, respectively, whereas DDT is converted to DDE. The primary residue of DDT, which persists to the present day in animals and humans after exposure over a decade ago, is DDE. Following biotransformation, these compounds distribute to tissues which are higher in neutral lipid content than are the major organs of metabolism and excretion, the liver and kidney. These lipid-rich tissues are relatively, deficient in the so-called mixed-function oxidase (MFO) enzyme systems necessary for biotransformation of the halogenated hydrocarbons to more polar and thus more easily excreted compounds. As a result, these lipophilic chemicals remain unchanged in adipose tissue with only limited amounts returning to the circulation for possible metabolism and excretion. Paradoxically, aldrin and heptachlor metabolism results in an increased rather than reduced body load. This is opposite of the pattern seen for most other pesticide classes. 

In the decade of the fifties impressive advances have been made by new pesticides. The chlorinated hydrocarbons (aldrin, chlordan, dieldrin, endrin, heptachlor, and toxaphene) have moved from a very meager output in 1950... 

Considerable research effort has been paid to the problems of the persistence of chemical means for the plant protection. Many of the studies have been aimed at the persistence of pesticides in the soil. Insecticides based on chlorinated hydrocarbons are particularly persistent, for instance DDT, BHC isomers and so-called polychlorinated cyclodiene compounds, aldrin, dieldrin, andrin, heptachlor. In many countries the use of these pesticides has been either restricted or even prohibited on account of their persistence in the environment. For chemical protection of plants they are gradually being replaced by organophosphate and carbamate substances, which are more toxic, but are less stable in the environment (e.g. parathion, dichlor-vos, carbaryl, propoxur). 

Biros interfaced a small time-averaging computer (Varian C-1024) with a GC-MS to scan and average repetitively a small portion of the mass spectrum (such as the molecular ion region), subtract background peaks, normalize, and plot the partial spectrum. This was done for several chlorinated hydrocarbon pesticide standards (25) and for heptachlor epoxide in human liver tissue (26). 

Heptachlor [76-44-8], another cyclodiene insecticide of chemical structure similar to chlordane is a chlorination product of chlordane. Technical grade heptachlor contains about 73% heptachlor, 22% fran -chlordane and 5% nonachlor. This pesticide was extensively used until 1970s for the control of soil insects, cotton insects, grasshoppers and termite control. The use of this pesticide for underground termite control was banned in the United States in 1988. Its application after that was restricted to controlling fire ant in power transformers. The U.S. EPA has classified heptachlor as a Group B2 probable human carcinogen. 

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