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During the past 70 years, humans have benefited from the production of a large array of chemicals including pesticides, pharmaceuticals, personal care product ingredients, cosmetics and plastics. Over this time period it is estimated that more than 80,000 different chemicals have been released in to the environment, with many released through the discharge of treated domestic wastewater treatment plant (WWTP) effluent. Exposure to some of these chemicals, specifically endocrine disrupting compounds (EDCs), elicits physiological responses in plants and animals, including fish.

Estrogenic EDCs present in WWTP effluents are capable of feminizing fishes downstream of WWTP discharges as well as producing contraceptive-like effects. These changes have been documented in fish in Colorado streams, including Boulder Creek below the city of Boulder, Colorado, 75th Street WWTP effluent discharge. In 2001, researchers from the Department of Integrative Physiology, at the University of Colorado, Boulder, and the United States Geological Survey (USGS) in Boulder, began to examine fish in Colorado at points upstream and downstream of domestic WWTP points of effluent discharge. Specifically in Boulder Creek below the WWTP discharge, sex ratios for white suckers (Catostomus commersoni) were skewed toward females almost 5:1. In addition, researchers observed intersex fishes below the effluent discharges but never at upstream reference sites. In subsequent collections, contraceptive-like effects were identified on the ovaries and testes of fish at the sites downstream of the effluent discharge suggesting reduced fertility as compared to fish at the reference site.

Few studies conducted to date in the United States to characterize the potential impacts of municipal WWTP discharges on fish feminization and the effects of EDC's on receiving waters, have been active joint efforts between the discharger and the research group. Since 2000, the city of Boulder Utilities Division has actively supported collaboration with researchers from the USGS and the University of Colorado, Boulder. The decision to be an active participant in the studies stems from the benefits the city sees from advancing the understanding of biochemical mechanisms involved in the observed effects on fish and possible strategies to reduce those effects.

The city and researchers have identified various opportunities for future collaboration to advance the current level of understanding of EDCs in the Boulder Creek environment and wastewater effluent. These opportunities include evaluating removal efficiencies of the current treatment process (trickling filter–solids contact secondary process) to removal efficiencies of the new activated sludge treatment process, which will go on-line in late 2007. In addition, the city is considering the potential benefits of developing a public education and outreach program to be implemented through the city's Public and Education Outreach Group, Public Works Communications Group and local agencies.
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Document Type: Research Article

Publication date: 2007-01-01

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