Chemical Characteristics

DDT is one of several typical chlorinated hydrocarbon insecticides discovered in the early 1940s and known for their persistent insecticidal activities, their lipophilic attributes, and their stable chemical properties. The insecticidal properties of DDT itself were discovered in 1939 by Paul H. Müller of Switzerland, who later received the Nobel Prize for his work. Since DDT was the first organic synthetic insecticide that possessed advantages such as low mammalian toxicity, wide spectrum, long-lasting properties, and low cost in comparison to arsenicals and other inorganic insecticides, most entomologists embraced its use to such an extent that more than 100 million pounds of DDT was being produced annually by the mid-1950s.

The insecticidal active ingredient of DDT preparations is p,p'-DDT (Fig. 1A). Its 1-dechlorination product, p,p'-DDD (Fig. 1B) retains reasonable levels of toxicity for some insects, but its dehydrochlorination product, p,p'-DDE (Fig. 1C), shows no insecticidal property, although p,p'-DDE could still have a toxic effect in other organisms. Other components often found in insecticidal DDT preparations are o,p'-DDT, p,p'-DDD, and o,p'-DDD. All these can be found as environmental residues.

DDE (dichloro-diphenyl-ethylene) one of the residues derived from DDT most frequently found in the environment, is produced mainly by metabolic activities in biological systems and is particularly prevalent in insects and in some mammalian species. Although both p,p'-DDE and o,p-DDE are found in the environment, the former is more abundant and more frequently encountered. In assessing residue levels of all DDT-derived compounds today, scientists express the entire spectrum of DDT-related (DDT-R) compounds or DDT-derived compounds as total DDT residue, or DDTs.

FIGURE 1 (A) 1,1,1-Trichlor-2,2-bis (p-chlorophenyl) ethane (p, p'-DDT). (B) p, p'-DDD. (C) p, p'-DDE.
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