Gender Blender

The Minnesota Department of Health is keeping a close eye on Adelman and Swackhamer's research, according to Hillary Carpenter, a toxicologist with the department. "There's a concern," Carpenter says. "The real question is concentrations, and whether humans are being exposed in sufficient quantities to cause an effect." The Minnesota Pollution Control Agency is also monitoring the research. Dan Helwig, a supervisor with the agency's Groundwater and Toxics Unit, says scientists are just beginning to understand the possible hazards posed by the "mosaic" of chemicals found in public waterways. Along with EDCs, a host of other substances, including pharmaceuticals, are showing up in effluent at trace levels. "Some of these chemicals are certainly toxic in higher doses. Are they toxic in the concentrations that have been found in fish and water? I doubt it. But they may have subtler effects," Helwig says.

The Mississippi waters near the channel still seem to have a robust walleye population--evidence that the EDCs are not having a catastrophic impact. But that doesn't mean there is no cause for worry. Even a small reduction in the reproductive capacity of the fish could create other problems by reducing the genetic diversity of future generations. The problem is, no one knows for sure how to pinpoint the short-term causes or long-term consequences.

"We have a lot of questions," says Swackhamer. "But we don't have a lot of answers."