I experienced cognitive dissonance while contemplating "Common pollutants undermine masculinity" (SN: 4/3/99, p. 213). If one-fifth to one gram of DEHP per kilogram is given to rats, then a 50 kg (110 lb.) human should receive 10 to 50 g of DEHP. If that much DEHP leached out of a dialysis system or IV bag and tubing, surely the whole apparatus would have disintegrated beforehand. Where is the research that shows that DEHP even leaches out of plastic in realistic solutions?

Michael Clover
Los Alamos, N.M.

According to the Chemical Manufacturers Association's Phthalate Esters Panel, "We are aware that some flexible vinyl medical devices allow phthalate esters to enter a patient's blood stream. ... Probably the most common potential for exposure occurs when patients receive fluids—nutrients, whole blood or blood components intravenously—from flexible vinyl bags or containers."

How close are human exposures to those producing toxicity in animals? In addition to the assertions on this question by Ted Schettler in the story, phthalate toxicologist L. Earl Gray says that some rats showing testes damage in experiments "had [DEHP] serum levels not too different from the dialysis patients." —J. Raloff

The specific feminizing effect of phthalate esters may be new information, but their general effects on fertility and birth defects are not. About 20 years ago, when Lake Michigan coho salmon became known as the world's most concentrated natural source of phthalate esters, I remember reading that mink farmers in Wisconsin and Minnesota switched to fish-cannery waste from the Great Lakes as mink feed. They had been getting that feed from the Pacific Northwest but switched to local sources because of cost. Birth rates immediately plummeted. They found that mink fertility was reduced essentially to zero or produced 100 percent birth defects when local fish constituted as much as one-third of the total diet. They quickly returned to their earlier source of waste fish. When will we learn?

Bill Beauman
Westmont, Ill.

I read with interest the article "Can this swamp be saved?" (SN: 4/17/99, p. 252). Good job. In 1977–78, I was a park ranger in the Division of Resources Management at Everglades National Park, and from 1978 through 1979, I was a hydrology technician in charge of research in Shark Slew in the park.

My research culminated in a restoration proposal that I presented before the research staff and director of the park. My search of the archives at the park revealed that research to save the Everglades had been going on for many years prior to my work there. It seems that research to save the Everglades is a self-perpetuating program that provides jobs but never reaches its goal. Over 30 years of research, hundreds of proposals, millions of dollars spent, and we are still at square one in actual implementation.

Robert L. Berger
Archer, Fla.