Lake CityA  beach on Lake Pepin, a stretch of the Mississippi River downstream from the Twin Cities. Sediments in the lake contain dioxins associated with hand soaps and other products.

A University of Minnesota study published today in the  scientific journal, Environmental Science & Technology, found that while overall dioxin levels in Mississippi River sediments are decreasing, dioxins associated with triclosan, a common ingredient in hand soaps, are rising significantly. The federal Food and Drug Administration last month said it would review the safety of triclosan.

Dioxins associated with triclosan were found in the sediments of Lake Pepin, a wide area in the Mississippi River downstream from the Twin Cities. The Minnesota study authors note that waste water treatment plants do not fully remove the triclosan pesticide, and that the human health impacts of the contaminants are unclear.

“These four dioxins only come from triclosan. They didn’t exist in Lake Pepin before triclosan was introduced,” University of Minnesota civil engineering professor William Arnold said. “In the most current sediments, these triclosan-derived dioxins account for about 30 percent of the total dioxin mass.”

Lake Pepin faces other pollution problems. The widest naturally occurring part of the Mississippi, it also suffers from algae blooms and turbidity. The Minnesota Pollution Control Agency is developing a complex cleanup plan that could require significant pollutant reductions from the Minnesota and St. Croix Rivers, which feed the Mississippi upstream from the lake.

Photo:  Lake City, Minnesota.