Pesticide lipophile

Unfortunately, there is a significant disadvantage resulting from appHcation of insect-resist agents from dyebaths it is impossible to ensure 100% exhaustion (transfer of pesticide from dyebath to fiber) and as a result, there is inevitably some environmental contamination. The extent of concern with this release of insect-resist agent depends on the spectmm of activity of the agent. If it is a broad-spectmm insecticide, especially one with reasonable persistence and lipophilic character, it is Hable to be reasonably toxic to aquatic insects and invertebrates, especially in certain environmental locations where... 

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). 

A formidable array of compounds of diverse structure that are toxic to invertebrates or vertebrates or both have been isolated from plants. They are predominately of lipophilic character. Some examples are given in Figure 1.1. Many of the compounds produced by plants known to be toxic to animals are described in Harborne and Baxter (1993) Harborne, Baxter, and Moss (1996) Frohne and Pfander (2006) D Mello, Duffus, and Duffus (1991) and Keeler and Tu (1983). The development of new pesticides using some of these compounds as models has been reviewed by Copping and Menn (2000), and Copping and Duke (2007). Information about the mode of action of some of them are given in Table 1.1, noting cases where human-made pesticides act in a similar way. 

Both PCDDs and PCDEs are refractory lipophilic pollutants formed by the interaction of chlorophenols. They enter the environment as a consequence of their presence as impurities in pesticides, following certain industrial accidents, in effluents from pulp mills, and because of the incomplete combustion of PCB residues in furnaces. Although present at very low levels in the environment, some of them (e.g., 2,3,7,8-TCDD) are highly toxic and undergo biomagnification in food chains. 

RH above can represent a very wide variety of xenobi-otics, including drugs, carcinogens, pesticides, petroleum products, and pollutants (such as a mixture of PCBs). In addition, endogenous compounds, such as certain steroids, eicosanoids, fatty acids, and retinoids, are also substrates. The substrates are generally lipophilic and are rendered more hydrophilic by hydroxy-lation. 

Hansch and Leo [13] described the impact of Hpophihdty on pharmacodynamic events in detailed chapters on QSAR studies of proteins and enzymes, of antitumor drugs, of central nervous system agents as well as microbial and pesticide QSAR studies. Furthermore, many reviews document the prime importance of log P as descriptors of absorption, distribution, metabolism, excretion and toxicity (ADMET) properties [5-18]. Increased lipophilicity was shown to correlate with poorer aqueous solubility, increased plasma protein binding, increased storage in tissues, and more rapid metabolism and elimination. Lipophilicity is also a highly important descriptor of blood-brain barrier (BBB) permeability [19, 20]. Last, but not least, lipophilicity plays a dominant role in toxicity prediction [21]. 

Residue analytical chemistry has extended its scope in recent decades from the simple analysis of chlorinated, lipophilic, nonpolar, persistent insecticides - analyzed in the first Si02 fraction after the all-destroying sulfuric acid cleanup by a gas chro-matography/electron capture detection (GC/ECD) method that was sometimes too sensitive to provide linearity beyond the required final concentration - to the monitoring of polar, even ionic, hydrophilic pesticides with structures giving the chemist no useful feature other than the molecule itself, hopefully to be ionized and fragmented for MS or MS" detection. 

Membrane-interactive compounds are lipophilic molecules which have high affinity for lipid membranes and consequently possess long membrane residence times. Examples include the lipophilic neutral molecules (cholesterol, lecithin, pesticides, oleyl alcohol, tocopherols, etc.) and large organic cations (chlorproma-... 

Of the 16 POPs listed in the 1998 Aarhus Protocol [27], 11 are organochloride pesticides, which have now been banned in several countries. Most concerns regarding these products relate to their toxicity, with health effects to humans ranging from lung damage and neurological problems to death. Many organochloride pesticides are lipophilic, and they accumulate in the adipose tissues. 

Grissom, R.E., Jr. C. Brownie, and F.E. Guthrie. 1987. In vivo and in vitro dermal penetration of lipophilic and hydrophilic pesticides in mice. Bull. Environ. Contam. Toxicol. 38 917-924. 

Synthetic musks have been detected in human tissues (Table 8) due to their lipophilic nature and their low biodegradability. The occurrence of these fragrance-related chemicals is subjected to a variable pattern with substantial interindividual differences, opposed to other environmental contaminants such as polychlorinated biphenyls (PCBs) or pesticides [165]. 

A mode of action need not involve enzyme inhibition. It could be a simple physical action. Cholestyramine resins are used to form nonpolar aggregates with lipophilic substances. With this action they constitute a good antidote for pesticide poisoning and can serve as a prophylactic in... 

The determination of OCP residues in milk has always presented problems, because the most common approach has required the total extraction of fat, together with lipophilic compounds, including organochlorine pesticide residues. Only one procedure for the extraction and separation of OCPs directly into an HPLC system has been described (11). The direct procedure injects the samples into an internal-surface reversed-phase C18 column connected online with the analytical column. 

Environmental. The high lipophilicity of the cydodienes and the prolonged persistence of dieldrin and heptachlor epoxide (soil half-lives 2—10 yr) have resulted in severe environmental contamination. These compounds are bioaccumulated from water to fish up to 100,000- to 300,000-fold and are ubiquitous in human fat and milk. Oxychlordane [26880-48-8], mirex, and chlordecone are also bioaccumulative. The cydodienes are extremely toxic to fish with LC5Qs (ppm) to trout and bluegill of endrin, 0.001-0.002 endosulfan, 0.001-0.003 diddrin, 0.003-0.015 aldrin, 0.006-0.01 heptachlor, 0.03-0.026 and chlordane, 0.022—0.095. The LD5Qs to pheasant and mallard are aldrin 16.8 and 520, dieldrin 79 and 381, and endrin 1.6 and 5.6 mg/kg. As indicated by their rat oral LD - s, they are also extremdy toxic to small mammals in fact, endrin has been used as a rodenticide (see Pesticides). Compounds, eg, aldrin and heptachlor, which have unsubstituted double bonds, readily add oxygen to form epoxides in plant and animal tissues and are preferentially concentrated and stored in animal fats. Aldrin epoxide (dieldrin) and heptachlor epoxide are more stable (half-lives on alfalfa of seven to eight days) than aldrin and heptachlor (half-lives on alfalfa of less than one day). 

Formulation additives used in topical drug or pesticide formulations can alter the stratum comeum barrier. Surfactants are least likely to be absorbed, but they can alter the lipid pathway by fluidization and delipidization of lipids, and proteins within the keratinocytes can become denatured. This is mostly likely associated with formulations containing anionic surfactants than non-ionic surfactants. Similar effects can be observed with solvents. Solvents can partition into the intercellular lipids, thereby changing membrane lipophilicity and barrier properties in the following order ether/acetone > DMSO > ethanol > water. Higher alcohols and oils do not damage the skin, but they can act as a depot for lipophilic drugs on the skin surface. The presence of water in several of these formulations can hydrate the skin. Skin occlusion with fabric or transdermal patches, creams, and ointments can increase epidermal hydration, which can increase permeability. 

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