Triclosan Undergoes Further Review

The antimicrobial agent triclosan, which is widely used in consumer products ranging from hand soaps to fabrics, has been found to promote liver tumors in mice (Proc. Natl. Acad. Sci. USA 2014, DOI: 10.1073/pnas.1419119111). Triclosan is not acutely toxic to mammals in the small amounts normally used, but its pervasiveness has led to questions about the consequences of long-term, low-level exposure. A team led by Robert H. Tukey of the University of California, San Diego, and Bruce D. Hammock of the University of California, Davis, used cell assays to determine that triclosan interacts with a receptor involved in metabolizing foreign chemicals. The team then studied the effects of triclosan fed to mice in their food or drinking water at amounts from about 30 to 70 mg/kg body weight per day for six to eight months, which equates to about 18 years for people. People who use triclosan-containing toothpaste are exposed to about 0.05 mg/kg body weight per brushing. The researchers found that the triclosan-exposed mice showed signs of liver injury. When researchers coupled triclosan exposure with exposure to a DNA-damaging agent, the mice developed more and larger liver tumors than they did with the DNA-damaging agent alone. The overall results suggest that triclosan-induced liver toxicity should be further evaluated in humans to determine appropriate uses in consumer products, the researchers say.