DDT group

DDT was the first of the modern insecticides. Its chemical structure is shown below. It is also called dichlorodiphenyltrichloroethane, and hence the name DDT. DDT was synthesized in 1873, but its insecticide activity was not discovered until 1939 by a Swiss entomologist, Dr. Paul Muller. Because of the millions of lives saved by the use of DDT during World 

War II, Dr. Muller ultimately received the Nobel Prize in medicine for his work. Although DDT has been banned from use in the United States (in 1973) and other Western countries, it is still a very important insecticide in India and African countries for malaria control. 

As shown in Table 4.1, technical-grade DDT contains mainly five isomers. The p,pf isomer, which accounts for about 70% of the total weight, is the toxic form of DDT and is usually called DDT. Several other isomers account for about 30% of the total weight the most abundant is o,p-DDT, about 20%. These isomers have little value as toxicants because they are less than l/10th as toxic as the p,p -isomer. DDT has an LD5() in rats of 250 mg/kg. 

Note There are ten other components with composition less than 1%. Source Adapted from Metcalf, R.L., Organic Insecticides, Interscience Publishers, New York, 1955. 

The DDT group insecticides are environmentally persistent because they have very low water solubility and vapor pressure and moderate stability to sunlight. For example, the water solubility of DDT is less than 2 ppb (parts per billion), and its vapor pressure is 1.5 x 10 7 mm Hg at 20°C. These compounds are also highly lipophilic and metabolically stable. As a result, they are persistent biologically and tend to bioaccumulate. The toxicity of this group is low 

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The Mode of Action of the DDT Group, Pyrethroids, Indoxacarb, and Sabadilla... 

Voltage-gated Na channels The DDT group, pyrethroids, Sabadilla Indoxacarb Delayed Na inactivation (Na channel modulators) Na channel blocker... 

COCHRANE AND CHAU OrganochloHne Residue Identity Residues The DDT Group and Some Cyclodienes... 

The neonicotinoids have very low fish toxicity, are not adsorbed through mammalian skin, and are not irritating or allergenic in the tests carried out so far. The pyrethroids (and DDT group) have a negative temperature correlation these insecticides are more active in warm weather. 

Stenersen, J. and Somme, L. 1963. Notes on cross-resistance and genetics of resistance to the DDT-group insecticides in the stable fly (Stomoxys calcitrans). Norsk Entomol. Tidsskrift., 12, 113-117. 

Apart from these obviously biogenic compounds only very few definite anthropogenic substances were identified. Within the group of xenobiotics 2,4 - and 4,4 -dichlorophenylmethane, DDT-derived metabolites, were most abundant. A pyrolytic conversion of related DDT metabolites to DDM cannot be excluded. Thus the occurrence of DDM in the pyrogram is only suggestive for DDT group metabolites in general. 

This investigation compares clinical courses, efficacies, adverse reactions and outcome of 115 consecutive, biopsy-proven polymyositis patients treated with ADT (32 patients) or DDT (83 patients). Mean onset ages, disease severity, incidence of malignancies and response rates did not differ between the ADT and DDT groups. 

Another SPR-based immunosensor for DDT, its metabolites, and analogues in real water samples was developed by Mauriz et al. Low limits of detection (LODs), in the sub-nanogram per liter range, were attained for DDT-selective (15 ng 1 ) and DDT group-selective immunoassays (31 ng 1 ). The SPR analysis of DDT proved to be three times more sensitive than colorimetric ELlSAs without the need of labeling combined with a much shorter time of respmise. This SPR biosensor portable platform (P-SPR) is also commercialized by the SENSIA company. 

Berg et al. [67] separated PCBs from chlorinated insecticides on an activated carbon column prior to derivatisation and gas chromatographic separation on a capillary column. Separation is based on the observation that PCBs adsorbed on activated charcoal cannot be removed quantitatively with hot chloroform but can be with cold benzene. Insecticides of the DDT group and a variety of others (eg g-BHC, Aldrin, Dieldrin, Endrin and Heptachlor and its epoxide) can be eluted from the charcoal with acetone-ethylether (1 3). Typical recoveries from a mixture... 

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