Tuesday, January 29, 2013
Triclosan, an antimicrobial agent used in many personal care products, commonly ends its useful life in municipal wastewater treatment plants, where chlorination causes it to break down into substances known as chlorinated triclosan derivatives (CTDs). Following exposure to sunlight, the CTDs further degrade into polychlorodibenzo-p-dioxins, which, like all dioxins, are carcinogenic. Because of the toxicity of these substances, researchers from the University of Minnesota collected sediment cores from seven lakes receiving treated wastewater and one lake with no wastewater inputs. The cores were then analyzed for the amount of triclosan and byproducts present, and, using radiometric dating, researchers were able to determine when triclosan entered the lakes. In all but one sample, the first appearance of triclosan matched with its introduction to the market in 1964. Generally, lakes showed an increase in levels of triclosan and its byproducts over time, unless wastewater treatment techniques were changed. For example, when wastewater treatment plants switched from chlorination to UV treatment to disinfect sewage, sediment levels of triclosan and its byproducts decreased. Data from the lake with no wastewater inputs showed much lower levels of triclosan, indicating that human use of triclosan and its presence in municipal wastewater is the primary source of these pollutants in lakes.
While the authors note that levels of triclosan and any byproducts are low, and that there are multiple sources of dioxins in aquatic environments, triclosan and byproducts may still negatively influence aquatic organisms. Likewise, because of the array of bioactive and persistent compounds in aquatic environments, there may be unknown consequences to the lakes and rivers receiving these treated wastewaters.
Written by: Corrie Layfield
Anger, C. T., C. Sueper, D. J. Blumentritt, K. McNeill, D. R. Engstrom, and W. A. Arnold. Quantification of triclosan, chlorinated triclosan derivatives, and their dioxin photoproducts in lacustrine sediment cores. Environmental Science and Technology., Just Accepted Manuscript. DOI: 10.1021/es3045289. Publication Date (Web): 15 Jan 2013