The negotiators of the global persistent organic pollutants (POPs) treaty will include country-specific exemptions for continued use of DDT for malaria control in the approximately two dozen countries still using it. Nevertheless, your article also notes that DDT may soon be unavailable in many malaria-stricken regions. To address this concern, countries should consider some form of insurance for current users of DDT and for those who need it for the future. Donald Robert’s suggestion of a single organization to manufacture and distribute DDT for countries truly needing it deserves serious discussion, as do other proposals, within the context of strengthened financial and technical assistance to malaria-control programs around the world.

Richard A. Liroff
World Wildlife Fund
Washington, D.C.

This article makes a persuasive case for continuing the use of this invaluable lifesaving chemical. However, it assumes without the slightest hint of skepticism that DDT is a “dreaded environmental pollutant.” It is time for the case against DDT—which rests almost exclusively on Rachel Carson’s 1962 book Silent Spring —to be reexamined. DDT was banned by the Environmental Protection Agency in defiance of massive volumes of scientific evidence. DDT did not kill songbirds or predators. DDT was incriminated for thinning eggshells, but only when birds were also deprived of calcium. Biomagnification, long persistence in the environment, carcinogenicity—all these allegations have been refuted.

Jane M. Orient
Tucson, Ariz.

DDT was banned in 1972 in the United States because of political reasons. DDT breaks down in the environment and loses its toxicity to insects in a few days. A main reason traces of DDT are found in environmental samples is that modern analytical techniques now have detection limits about 6 orders of magnitude better than about 20 years ago. Misidentification occurs quite often. For example, red algae produce halogen compounds that are misidentified as DDT by gas chromatography. The World Wildlife Fund and the World Health Organization are completely wrong in their attempt to get DDT banned. About 2.7 million people die annually from malaria, and 500 million clinical cases of malaria occur each year. It is way past time to stop politicians and so-called environmentalists from overruling good science.

Jack L. Woods
Ogden, Utah

While the letters by Orient and Woods (above) railing against the prohibitions of DDT were probably published in the interest of editorial balance, scientific debate is not well served when political beliefs and flawed logic are substituted for reasoned discourse based on real data. The well-documented decline of the California brown pelican and its correlation with DDT use is no longer debated. Bioaccumulation of DDT is demonstrated on a regular basis. DDT, banned in the United States over 25 years ago, is routinely detected at high concentrations in investigations of former pesticide manufacturing and shipping facilities and in low concentrations in many locations. Orient denies these phenomena. Woods attempts to bolster his argument by stating that compounds from red algae could be misidentified by gas chromatography as DDT. However, most environmental samples don’t contain red algae. Additionally, if the identity of a chemical is uncertain by gas chromatography alone, environmental labs typically will confirm the analysis using mass spectroscopy. As a geochemist well into my second decade of environmental consulting, I feel that environmental regulations in some cases are overly strict or misapplied by individual regulators, and environmental decisions are often overly influenced by emotional arguments both pro and con. The U.S. ban on the sale and use of DDT is not one of these cases.

Jay A. Ach
San Francisco, Calif.

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