Contaminants identified in Boulder Creek included ethinylestradiol -- a chemical used in most contraceptives -- as well as other reproductive steroids produced naturally by humans. Estrogen-related chemicals found in the water included bisphenyl A and phthalates associated with plastic, nonylphenols associated with detergents, and pesticides. Most of the compounds came from products flushed down toilets and drains, according to Norris.
In the new study following the treatment plant upgrade, the team studied adult male fathead minnows in 100 percent effluent water, those in a mixture of half effluent and half upstream water, and those in tanks containing all upstream water. Norris and his team saw no effects on male sex characteristics of the minnows in the tank containing 100 percent effluent water directly from the treatment plant until 28 days after exposure.
As part of the study, Norris and his colleagues also analyzed reproductive organs from preserved fish specimens from CU's Museum of Natural History that had been collected from Boulder Creek between 50 and 100 years ago. The researchers and found no evidence of feminized or intersex fish in the museum specimens, he said.
The CU research team also tested brown trout populations below a wastewater treatment in Vail, Colo., said Norris. The trout showed no increases in vitellogenin.
In addition to chemicals that trigger fish feminization, biologists are finding increased concentrations of fluoxetine, a common antidepressant taken by millions of Americans, in waterways across the nation, said Norris. Fluoxetine has been shown to enter the brains of fish and affect fish behavior, said Norris.
Between 2000 and 2002, Norris and his group were among the first in the nation to document the problem of intersex fish following their stream surveys of Boulder Creek, the South Platte River near Denver and Fountain Creek near Colorado
|Contact: David Norris|
University of Colorado at Boulder