A group of researchers at the University of California, Davis and the University of Colorado have reported that Triclosan [5-chloro-2-(2, 4-dichlorophenoxy) phenol; an antibacterial chemical widely used in hand soaps] hinders muscle contractions at cellular level, slows swimming in fish and reduces muscular strength in mice. This important finding has been published on August 13, 2012 in an issue of PNAS under the title, “Triclosan impairs excitation-contraction coupling and Ca2+ dynamics in striated muscle”. The investigators performed several experiments to evaluate the effects of triclosan on muscle activity by using doses similar to those that people and animals may be exposed to during everyday life. In test tube experiments, triclosan impaired the ability of isolated heart muscle cells and skeletal muscle fibers to contract. Specifically, the team evaluated the effects of triclosan on molecular channels in muscle cells that control the flow of calcium ions through creating muscle contractions. The team also found that triclosan impairs heart and skeletal muscle contractility in living animals. Moreover, anesthetized mice had up to a 25-percent reduction in heart function measures within 20 minutes of exposure to the chemical. In addition, the mice had an 18-percent reduction in grip strength for up to 60 minutes after administration of a single dose of triclosan. Finally, the investigators looked at the effects of triclosan exposure on fathead minnows (a small fish commonly used as a model organism) and observed a significant reduction on swimming activity after seven days of exposure. However, researchers have cautioned that translating results from animal models to humans is a large step and would require further study. But the outcomes were striking in a number of animal models – a fact that provides strong evidence on the diverse effect of triclosan at current levels of exposure. [summarized by the graduate student Samsad Razzaque]