Chlorinated aromatic compounds pesticides

Much of the effort on environmental chemicals that contaminate food has concentrated on a small range of chlorinated chemicals. In addition to the chlorinated PCDDs, PCDFs and PCBs already mentioned, other chlorinated compounds can be separated into two groups chlorinated aromatic compounds and chlorinated aliphatic compounds. Although there is a number of organochlorine pesticides that are persistent in the environment, these will not be considered here, as they comprise an extensive field of study in their own right. 

This chapter provides an overview of some of the LC methods used in the determination of persistent organic contaminants in environmentally relevant samples and associated measurement issues. Emphasis has been placed on compounds and groups of compounds included in the Stockholm Convention, including PAHs, chlorinated aromatic compoimds, pesticides, BFRs, and PFAAs, with a focus on research carried out since 2000. Purely GC-based methods have been excluded from this discussion, as have reports that emphasize sample cleanup and processing research. Excellent reviews of these topics have been published previously [6—13]. 

Apart from pesticides, chlorinated aromatic compounds have attracted, and continue to attract, more attention from scientists, legislative bodies, and pressure groups than any other class of compound. Polychlorinated biphenyls (PCB) are by far the best known members of the class, but many other chlorinated products, and some brominated materials, have considerable commercial significance. Fluorine and iodine derivates are of little importance, and will not be considered. 

The biological activity of several halogenated herbicides in water is destroyed by ultraviolet irradiation (18). Irradiation seems to be a promising method for decontaminating small quantities of pesticides. The chemical similarity between the chlorinated dioxins and other chlo-rinted aromatic compounds suggested that if there were parallels in their photochemical behavior, sunlight might destroy dioxins in the environment. 

Benzene and its derivatives are used widely throughout the chemical industry as solvents and raw materials. Mono-, di-, and trichlorobenzenes are used directly as pesticides for their insecticidal and fungicidal properties. Benzene, toluene, and chlorobenzene are used as raw materials in the synthesis of at least 15 pesticides, although their main use is as a carrier solvent in 76 processes. Additional priority pollutant aromatics and chlorinated aromatics exist as impurities or as reaction byproducts because of the reactions of the basic raw materials and solvent compounds. 

The vendor claims that the Ariel SST can process soils at rates up to 400% higher than an incineration process. They also state that the technology has been applied to all ranges of petroleum contaminants, including crude oil, as well as nonchlorinated hydrocarbons, chlorinated hydrocarbons, chlorinated pesticides, and polynuclear aromatic compounds. 

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... 

The solvent extracts can be cleaned up by traditional column chromatography or by solid-phase extraction cartridges. This is a common cleanup method that is widely used in biological, clinical, and environmental sample preparation. More details are presented in Chapter 2. Some examples include the cleanup of pesticide residues and chlorinated hydrocarbons, the separation of nitrogen compounds from hydrocarbons, the separation of aromatic compounds from an aliphatic-aromatic mixture, and similar applications for use with fats, oils, and waxes. This approach provides efficient cleanup of steroids, esters, ketones, glycerides, alkaloids, and carbohydrates as well. Cations, anions, metals, and inorganic compounds are also candidates for this method [7],... 

Chlorinated aromatics are of special interest due to their extensive use as solvents and fumigants (e.g., dichlorobenzene), wood preservatives (e.g., pen-tachlorophenol), and as parent compounds for pesticides (e.g., 2,4-dichlorophenoxiacetic acid, also known as 2,4-D). An example of their biodegradation is that of 2,4-D, which takes place through a modified ort/io-cleavage pathway by enzymes that are not specific for their substrates. See Figure 9.11. The products, acetylSCoA and succinate, are part of... 

Application Sulfuryl chloride is used as a chlorination and sulfochlorination agent in the organic chemical industry, in particular for selective chlorination (e.g. for the side chains of aromatic compounds) and in the manufacture of organic intermediates for dyes, pharmaceuticals, pesticides and disinfectants. 

The complexity of the immune system renders it readily attacked by many chemicals. Such attack may result, for example, in organ damage in the thymus, bone, and lymph nodes as well as in cellular pathology in immunocompetent cells. More than 350 different compounds have been identified as immunotoxinsJ5 6 Table 25.1 contains a representative list of these. This list includes heavy metals, chlorinated and organophosphorus pesticides, aromatic hydrocarbons, polynuclear aromatic hydrocarbons, organic solvents, and many widely used chemicals. Many lipophilic and hydrophilic chemicals are immunotoxins and the immunotoxicity of these compounds is manifest via multiple mechanisms. 

More than 800 chemicals have been identified as being toxic to the skin. These include aliphatic, aromatic and chlorinated hydrocarbons, alcohols, esters, ethers, glycols, aldehydes, ketones, inorganic oxidizers, heavy metals, acids, alkalis, pesticides, plasticizers, polynuclear aromatic compounds, POPs, and surfactants J1-3 A partial list of these is contained in Table 27.1. A more complete list is available on the Scorecard web site.I3 ... 

Chlorinated Aromatic Hydrocarbon Environmental Toxins. As a result of human endeavor, toxic compounds containing chlorinated benzene rings have been widely distributed in the environment. The pesticide DDT and the class of chemicals called dioxins provide examples of chlorinated aromatic hydrocarbons and structurally related compounds that are very hydrophobic and poorly biodegraded (Fig. 5.28). As a consequence of their persistence and lipophilicity, these chemicals are concentrated in the adipose tissue of fish, fish-eating birds, and carnivorous mammals, including humans. 

Reductions Microbial and mammalian nitroreductase reduces nitro compounds to amines. Chlorinated alkanes and alkenes are common contaminants in ground water and chlorinated aromatics, PCBs, organochlorine pesticides, are often detected in soils and sediments and it has been of interest to evaluate the potential for these compounds to be metabolized. A number of microorganisms are able to dechlorinate both halogenated aliphatic and aromatic compounds in a reduction reaction." It has been observed that the more highly chlorinated congeners are more reactive in these systems in contrast to the response in oxidative dechlorinations. 

Chlorinated organic compounds (COCs) refer to the substitution of one or more hydrogen in aliphatic and aromatic hydrocarbons and their derivatives by chlorine. COCs are widely used in the fields of chemistry, medicine, electronics, pesticides, etc. Many COCs are endocrine disturbance substances, show carcinogenic effects, and have been listed as priority pollutants by the US Environmental Protection Agency (USEPA). When released into the environment, COCs are transported in both air and water. However, COCs are chemically stable and difficult to destroy, and they are eventually deposited in soils and sediments due to their hydrophobic-ity. Soils and sediments contaminated with COCs are long-term sources of pollutants and pose great threats to human health and ecosystems. Therefore, remediation of these contaminated soils and sediments is of great importance. 

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