Science Fair Project Encyclopedia
Insecticides are very widely used in agriculture, as well as in people's dwellings and workplaces. The use of insecticides is one of the major causal factors behind the increase in agricultural productivity in the 20th century.
Some insecticides have been banned due to their adverse effects on animals or humans.
DDT is an example of a heavily used and misused pesticide. One of the better known impacts of DDT is to reduce the thickness of the egg shells on predatory birds. The shells sometimes become too thin to be viable, causing reductions in bird populations. This occurs with DDT and a number of related compounds due to the process of bioaccumulation, wherein the chemical, due to its stability and fat solubility, accumulates to progressively higher concentrations in the body fat of animals farther up the food chain. The near-worldwide ban on DDT and related chemicals has allowed some of these birds--such as the peregrine falcon--to recover in recent years.
Some of the newer insecticides are more specific in their actions and are designed to break down into non-toxic components within a few days of application.
Several are now banned because of their ecological persistence:
Chemically similar to Nerve agents
Plant toxin derived
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