Soy estrogen laces paper-mill wastes.

Scientists have attributed many of soy's heart-healthy and anticancer benefits to its rich supply of several estrogen-mimicking compounds. One of these, genistein, has now been found in trees, which explains why significant amounts of the hormonal pollutant taint paper-mill effluent.

Biologists have been examining paper-mill wastes as a likely source of chemicals contributing to the delay or lack of fertility seen in some Great Lakes fish over the past decade (SN: 11/4/95, p. 295). Initially, researchers focused on the mills' release of sitosterol, a bark-derived compound that can mimic estrogen.

Genistein is one member of a huge class of plant compounds known as flavonoids. Chris Metcalfe of Trent University in Peterborough, Ontario, and his colleagues had read scientific accounts of flavonoids in trees that might also have hormonal alter egos. So, they went on a flavonoid hunt.

"To our surprise," Metcalfe told SCIENCE NEWS, "genistein was the only hit that we got." No previous analysis had ever found it in trees, he says.

Last year, Metcalfe's group reported finding other natural and synthetic estrogens in municipal wastewater at concentrations sufficient to alter the reproductive development of medaka, a fish that's an aquatic analog of the lab rat (SN: 6/17/00, p. 388). He says the concentrations of genistein in paper-mill effluent are "certainly" high enough to similarly affect medaka.

The researchers found the flavonoid at 30 micrograms per kilogram in wood pulp and 10 to 13 micrograms per liter in mill effluent. Genistein concentration was unchanged by bleaching and water treatment of the effluent.

A report of these findings will appear in an upcoming issue of ENVIRONMENTAL SCIENCE & TECHNOLOGY.