Estrogen can bend gender of male fish living in water contaminated by birth-control pill residue
By Seth Borenstein

WASHINGTON - The female hormone estrogen can bend the gender of male fish that live in bodies of water contaminated with the residue of birth-control pills, a new study indicates.

For three years, Canadian scientists have put birth-control pills into a remote Ontario lake to measure this impact. The results: All male fish in the lake - from tiny tadpoles to large trout - were "feminized," meaning they had egg proteins growing abnormally in their bodies.

The experiment was intended to match the impact that the female hormone estrogen may be having on many American bodies of water, as city sewage systems empty waste into them that is contaminated with residue from birth-control pills.

One-third of male Pearl Dace minnows grew eggs in their testes. The entire population of the common Fathead minnow, once numbering in the several thousands, crashed to near zero because the hormone-stoked fish couldn't reproduce.

"Any fish species we have in the lake, any male is responding to the estrogen," said Karen Kidd, a research scientist at the Canadian Freshwater Institute and the study's chief researcher. She presented her findings to the American Chemistry Council this week. "It is a feminization. ... It's enough to be concerned about what's going on in the bigger picture (from estrogen)."

Kidd's research - the most controlled experiment ever to look at the effects of estrogen on ecosystems - has heightened concerns that human female hormones may be hurting wildlife, said several scientists in the U.S. government.

Scientists are looking at whether estrogen and chemicals that act like estrogen are affecting human males, as well, said Mike Mac, the director of the U.S. Geological Survey's Columbia Environmental Research Center. He noted that a study earlier this month in the journal Environmental Health Perspectives found that rural men exposed to certain pesticides that act like estrogen had lower sperm counts.

Kidd's $925,000 study is mostly funded by the Canadian government, with help from the U.S. Environmental Protection Agency and private industry.

Estrogen gets into waterways through a familiar path. Millions of women take different types of estrogen in birth-control pills and hormone replacement therapy; Kidd's study used the synthetic estrogen called ethynylestradiol, or EE2. When the women urinate, the estrogen passes into sewer systems, where bacteria eat much but not all of it. The remaining estrogen leaves sewage-treatment plants and flows into rivers, lakes and streams along with the treated wastewater.

"We do not have a good handle on what's (coming out of) these sewage treatment plants in this country yet," said Jim Lazorchak, the acting chief of the EPA's molecular ecology branch in Cincinnati, who has worked with Kidd on the lake experiment. "This is a very emerging issue."

Scientists have suspected for years that estrogen from humans is at least partially to blame for strange animal sexual oddities - such as hermaphrodites, which have both male and female characteristics - but other hormones and common chemicals also are thought to disrupt animals' endocrine systems. As a result, scientists have had a difficult time finding a direct cause-and-effect example in the wild. Kidd's study shows that link.

The clarity of the result stems from the fact that Kidd used Canada's unique Experimental Lakes Area, a range of 85 unpolluted lakes hours from any city. For 35 years the Canadian government has set it aside for experiments in environmental science.

Since 2001, Kidd and her colleagues have put birth-control pills into one lake three times a week every summer. She then compared the fish in the lake to those they found there in 2000 and to those in two control lakes where no estrogen was added.

Kidd seeded the lake with 5 nanograms of EE2 for every liter of water, a level roughly equivalent to a typical U.S. urban waterway, said Larry Barber, a USGS geochemist who studied the prevalence of estrogen in 70 U.S. rivers, lakes and streams. In Barber's study, four U.S. sites - in Florida, New York state, Massachusetts and Montana - had EE2 levels many times higher than in Kidd's lake. The Florida site, near Moriczville, had 273 nanograms per liter, according to Barber's study.

"The study in the experimental lakes shows that EE2 as an environmental contaminant has an important ecological impact," Barber said. "This is an issue in the U.S."

But there's hope, Kidd said.

Bacteria that occur naturally in lakes and are used for treatment in sewer plants consume the estrogen in water. The answer to the estrogen problem in waterways could be simply to arrange for more prolonged bacteria treatment in sewer plants, she said.

"These are issues that are starting to come to the fore a little bit more now," said Adam Krantz, a spokesman for the Association of Metropolitan Sewerage Agencies. "We're waiting to see what the science shows us. We're tracking it."