Chlorine and Triclosan: The Facts

June 3, 2010

A 2003 study1 by Virginia Tech researchers found chloroform can be formed by the chemical reaction of chlorinated drinking water with the widely used antimicrobial agent triclosan. Additionally, the researchers suggested that chlorine and triclosan could react to form dioxins in the presence of sunlight.

Unfortunately, some promotional materials and press stories related to this study raise misleading and unwarranted fears about potential health implications of the research findings. The Chlorine Chemistry Division of the American Chemistry Council offers the following points in response to these concerns:

  • Chlorine is added to drinking water to destroy disease-causing organisms, an essential step in ensuring safety. In the United States, chlorine has helped to virtually eliminate waterborne diseases such as cholera, typhoid and dysentery.
  • Exposure to low levels of chloroform does not cause cancer. While high doses of chloroform have been shown to cause cancer in laboratory animals, the U.S. Environmental Protection Agency (EPA) has concluded that chloroform is not likely to be carcinogenic to humans unless exposure levels are high enough to first cause other toxic effects. EPA's drinking water regulations for chloroform are set well below levels that may cause such effects, even in sensitive populations.
  • The experiments conducted by Virginia Tech researchers likely overstate the potential for chloroform formation from typical household uses of products containing triclosan. The reported levels of chloroform formation were reached only after two hours of triclosan and chlorinated water interaction. Furthermore, chlorine levels in household tap water are generally much lower than the levels used in the experiments.
  • In the presence of sunlight triclosan may chemically transform to produce up to four dioxin compounds. Dioxin is not one compound, but a family of compounds of widely ranging toxicity. Of the 210 dioxin and furan family compounds, only 17 are considered to pose a potential public health concern. The dioxin compounds created by the "phototransformation" of triclosan are 2,8-DCDD, 2,3,7-TCDD, 1,2,8-TriCDD, and 1,2,3,8-TCDD. These, however, are generally not considered to be toxic to humans or wildlife because they do not share the same chemical structure as the other dioxins.
  • A recent study2 by University of Minnesota researchers analyzed two sediment cores and found that over the last 30 years the levels of the four dioxins derived from triclosan have increased by 200 to 300 percent. However, the same samples also showed that levels of all other dioxins have decreased by 73 to 90 percent. This decrease is consistent with numerous studies that show similar declines of dioxins in all media over the past 20 to 30 years.
1Rule, K.L., Ebbett, V.R., Vikesland, P.J. (2005). Formation of chloroform and chlorinated organics by free-chlorine-mediated oxidation of triclosan. Environ. Sci. Technol., 39(9), 3176-3185.
2Buth, J.M., Steen, P.O., Sueper, C., Blumentritt, D., Vikesland,P.J., Arnold, W.A., and McNeill, K. (2010). Dioxin photoproducts of triclosan and its chlorinated derivatives in sediment cores. Environ. Sci. Technol. (Available on-line).
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