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Study Finds Increasing Levels of Antibacterial Agent in MN Lakes Lake Harriet, MN

A new University of Minnesota study has determined that a common antibacterial agent called triclosan can be found in increasing levels in several of Minnesota’s freshwater lakes. The University says the findings are directly linked to increased triclosan use over the past few decades.  The compound is commonly used in bath soaps, dish soaps, toothpastes, and similar products.  Researchers also found an increasing amount of other chemical compounds, called “chlorinated triclosan derivatives,” that form when triclosan is exposed to chlorine during the wastewater disinfection process. When exposed to sunlight, triclosan and its chlorinated derivatives form dioxins that have potential toxic effects in the environment. These dioxins were also detected in the lakes included in the study.

"It’s important for people to know that what they use in their house every day can have an impact in the environment far beyond their home," said the study’s lead author William Arnold, a civil engineering professor in the University of Minnesota’s College of Science and Engineering. "Consumers need to know that they may be using products with triclosan. People should read product labels to understand what they are buying."  Arnold said the research can also help chemical manufacturers understand some of the potential long-term impacts on the environment that are linked to triclosan.

The researchers studied the sediment of eight lakes of various sizes throughout Minnesota with varying amounts of treated wastewater input. They 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 different lakes with various wastewater treatment inputs," Arnold said. "While wastewater treatment removes the vast majority of triclosan, these systems were not designed with this in mind. We need to continue to explore all aspects of this issue."

Click here to read the University of Minnesota’s full research paper, published on the Environmental Science and Technology website.






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