Norris, a professor of integrative physiology at CU-Boulder, said the multimillion-dollar general upgrade of the Boulder Wastewater Treatment plant northeast of Boulder, Colo., designed to solve multiple problems has had a dramatic effect on delaying symptoms of male fish feminization. The team compared fish populations below the wastewater treatment plant on Boulder Creek in 2006 before it had upgraded and again after the upgrade had been completed.

Norris participated in a press briefing at the Endocrine Society's 92nd annual meeting held June 19-22 in San Diego. Other team members included Alan Vajda of the University of Colorado Denver, Ashley Bolden and John Woodling of CU-Boulder, Larry Barber of the U.S. Geological Survey's Water Resource Division in Boulder and Heiko Schoenfuss of St. Cloud University in Minnesota.

In the 2006 study Norris and his colleagues used a mobile fish exposure facility situated on Boulder Creek northeast of Boulder that collected both water from upstream of the plant and effluent water directly from the treatment plant. After exposure to equal parts of effluent and upstream water for only seven days, adult male fathead minnows became feminized, looking and acting like females and showing elevated levels of a protein known as vitellogenin that is normally produced by females.