Arnold said this research can also help chemical manufacturers understand some of the potential long-term impacts from triclosan on the environment.
The researchers studied the sediment of eight lakes of various size throughout Minnesota with varying amounts of treated wastewater input. They gathered sediment cores about one meter long from each of the lakes. After slicing the cores into several segments about two to four centimeters in thickness, they worked with researchers at the Science Museum of Minnesota's St. Croix Watershed Research Station to date the sediment. Some sediment segments dated back more than 100 years. Professor Arnold's group and researchers from Pace Analytical Services in Minneapolis used high tech methods to analyze the chemicals contained in the sediments over time.
The research found that sediment collected from large lakes with many wastewater sources had increased concentrations of triclosan, chlorinated triclosan derivatives, and triclosan-derived dioxins since the patent of triclosan in 1964. In small-scale lakes with a single wastewater source, the trends were directly attributed to increased triclosan use, local improvements in treatment, and changes in wastewater disinfection since the 1960s. When UV disinfection technology replaced chlorine in one of the wastewater treatment plants, the presence of chlorinated triclosan derivatives in the sediments decreased.
In the lake with no wastewater input, no triclosan or chlorinated triclosan derivatives were detected. Overall, concentrations of triclosan, chlorinated triclosan derivatives, and their dioxins were higher in small lakes, reflecting a greater degree of wastewater impact.
"The results were similar to other recent studies worldwide, but this was the first broad study that looked at several dif
|Contact: Rhonda Zurn|
University of Minnesota