DDT is a member of a class of acetylcholinesterase inhibitors called chlorinated hydrocarbons. It was developed shortly before or during WWII and found immediate use in controlling the mosquito population, vectors to numerous blood-borne tropical diseases. It has very low toxicity to humans and other vertebrates. Use of DDT resulted in a dramatic lowering of noncombat-related casualties in tropical areas.

One of the major causes of noncombat deaths in time of war, throughout history, was typhus. Use of DDT dust by Allied armed forces in the clothing, on the person, and often in the dwellings of civilians was forced at gunpoint under martial law in Europe. WWII had the lowest civilian mortality due to disease of any modern war, in no small measure to the use of DDT.

DDT was used in the coastal areas of the USA following WWII to control mosquitoes. The use of DDT virtually eradicated malaria and yellow fever from the USA, diseases which since colonial times had claimed many, many thousands of lives.

DDT was then turned to crops. It was cheap and abundant and in the USA, was used for damn near every pest known to man.

Unfortunately, DDT (and many other chlorinated hydrocarbons that were developed subsequent to DDT) were over-used and misused, due to ignorance. Few people knew enough to be concerned and even those who knew of the dangers were also cognizant of the tremendous benefits that the chlorinated hydrocarbons had afforded mankind. Unfortunately, chlorinated hydrocarbons are very persistent. They accumulate readily in the fatty tissues of all animals. So sublethal doses in (say) insects accumulate in insect fat stores. Chlorinated hydrocarbons also persist for a long time in soil under certain conditions that lower the oxygen concentration.

Predators of insects (stop and think a moment about the number of species that prey on insects, including other insects) consume the contaminated fats. Animals that consume large quantities of insects (bats, many birds, fish, reptiles, etc) accumulate the fats of insects that consumed the chlorinated hydrocarbons. This increases the concentration of hydrocarbons in the organisms up the food chain.

We now understand the risks and benefits of DDT and many other species of chemicals. By conducting basic science on a large number of organisms around the world, we understand far, far better than we ever have before, what the risks and benefits of pesticide use will be.

Of all the chemicals developed since DDT, it is surprising that DDT is more benign that most subsequent chemicals. DDT was the first so it got all of the attention.

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