Malaria is one of the world's worst killers. It infects between 300 and 500 million people a year, killing more than 1 million, many of them children. Malaria is a parasite that is carried by mosquitoes from one person to another.Pesticides have a role in combating malaria, as well as other deadly mosquito-borne diseases such as dengue fever.

Yet controversy surrounds the application of insecticides to fight disease. The weapon that seems to be the most effective against malaria is DDT, which many people consider to be so environmentally harmful that it should not be used.

Thus, environmentalists who oppose the use of DDT are pitted against public health officials in a grim dispute. Janet Raloff, a science reporter, summarizes the issue this way:"Though environmentalists have come to demand this poison's elimination from the face of the earth, some tropical-disease specialists laud DDT...