Letters.

Reconsidering DDT 

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 ("The case for DDT," SN: 7/1/00, p. 12).

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.

"The case for DDT" 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 

Offers crispy critters

I read "Cicada subtleties" (SN: 6/24/00, p. 408) with great interest. There was a minor emergence of periodical cicadas this year in the area. However, despite what the article says, I don't believe it was a brood emerging 4 years early. In 1983, 4 years before the last major emergence, there was a similar minor emergence. The 2000 emergence is presumably the descendents of the 1983 brood coming out right on schedule. I have a few exoskeletons from 1983, 1987, and 2000, if anyone wants to study them.

Bobby Baum Bethesda, Md.