Water Resources Center

The Water Resources Center is affiliated with the College of Food, Agricultural and Natural Resource Sciences and University of Minnesota Extension.

WRC-sponsored study finds rising dioxin levels from common antibacterial agent in Mississippi sediments

WRC-pubs-minnegramonline-sept10-billarnold-imgSpecific dioxins derived from the antibacterial agent triclosan, used in many hand soaps, deodorants, dishwashing liquids and other consumer products, account for an increasing proportion of total dioxins in Mississippi River sediments, according to new University of Minnesota research funded by a grant from the National Science Foundation and the Water Resources Center. A research team lead by Water Resources Sciences professor Bill Arnold (pictured left) found that over the last 30 years, the levels of the four dioxins derived from triclosan have risen by 200 to 300 percent, while levels of all the other dioxins have dropped by 73 to 90 percent.

Earlier research conducted by Arnold’s group showed that triclosan generated a specific suite of four dioxins when exposed to sunlight. In this recent study, core samples of Lake Pepin sediments, which contain a 50-year record of pollutant accumulation, were analyzed for triclosan, the four dioxins derived from it, and the entire family of dioxin chemicals. “In the deepest part of the sediment, there is no triclosan and these dioxins are not present,” Arnold said. “Once triclosan was introduced, a record of triclosan and these four dioxins appears in the sediment.” Triclosan was added to commercial liquid hand soap in 1987, and by 2001, about 76 percent of commercial liquid hand soaps contained it. In fact, it’s so prevalent, that seeking a liquid soap without triclosan is challenging—Arnold’s own wife spent a half an hour walking the aisles of a supermarket trying to find a hand soap that didn’t contain it.

About 96 percent of triclosan from consumer products goes down residential drains, and much of it eventually reaches wastewater treatment plants, where it is not completely removed. When treated wastewater is released into rivers, sunlight converts some of the triclosan into dioxins. “Neither toxicity of the dioxins derived from triclosan nor the extent of the dioxins distribution in the environment is well understood,” said Arnold. “But we do know that soap without triclosan works perfectly well.”