Updated Aug. 16, 2007 12:01 am ET

Last year, the World Health Organization reversed a 25-year-old policy and recommended using the pesticide DDT to fight malaria in the Third World. A new study published in the public health journal, PLoS ONE, provides more evidence that the decision was long overdue.

The U.S. and Europe solved their malaria problem a half-century ago by employing DDT, but the mosquito-borne disease remains endemic to the lowland tropics of South America, Asia and Africa, where each year a half-billion people are infected and more than a million...