Chlorinated pesticides behavior

By definition, any pesticide has toxic effects on organisms. Listed pesticides are those that combine high toxicity with resistance to degradation in the environment. Moore and Ramamoorthy109 review the behavior of chlorinated pesticides in natural waters. 

Researchers were also able to establish the link between declines of other predatory species such as the European sparrowhawk and the use of organo-chlorine pesticides other than DDT. For instance, the cyclodiene insecticides aldrin, dieldrin, and he-ptachlor used as seed treatments caused massive mortality of both seed-eating species and their predators. All of the insecticides had the following points in common they were highly soluble in fats and refractory to metabolism. The impacts on the predatory species typically take place in periods of food stress when fat soluble residues are released from fat stores and returned into general circulation. In a food-stressed individual, the brain remains as the most lipid rich tissue and this is where contaminants move to. Toxicity results when threshold values in brain tissue are exceeded. At sublethal levels, documented effects of cyclodiene insecticides in birds have included changes in their reproductive, social, and avoidance behaviors. 

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. 

Organophosphoric esters are very effective and degradable pesticides [304], which makes them preferable to their chlorine-based counterparts. Their hydrolysis behavior is well known [305], the final product being the orthophosphate ion. But these compounds are very toxic to humans because of their inhibiting effect on acetylcolinesterase as little as a few ppm can be lethal [306]. 

While chlorinated derivatives are potent herbicides, the structurally related alkyl-substituted phenoxyalkylcarboxylic acids have no pesticidal effect. These compounds are mentioned here because their chromatographic behavior is similar to that of these herbicides. Their separation was studied on reversed-phase TLC (RPTLC) plates having different lengths of carbon chains chemically bonded to silica layers using different mobile phases. This work could provide a possible means for chromatographic studies on their chlorinated derivatives (88) (Table 7). 

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