Americans and Europeans have been slathering triclosan on ever since hospitals began using it in antibacterial soaps and sanitizers 40 years ago. But that era may be passing, especially after the release this week of a University of California, Davis and University of Colorado study showing that the widely used chemical impairs muscle functions, including the heart. Experts say beyond its use in toothpaste to help fight gingivitis, the health benefit of triclosan in a slew of other consumer products has not been proven. There’s been a drumbeat going about the potential harm it may be doing for some time. The activist group Beyond Pesticides pounds triclosan ever chance it gets, while the industry’s Washington D.C.-based American Cleaning Institute instantly charged the two PAC 12 universities “crossed the line into straight advocacy,” coming to “questionable conclusions” in the study. The findings appear online in the Proceedings of the National Academy of Sciences of the United States of America. Copies of the study, titled “Triclosan impairs excitation-contraction coupling and Ca2+ dynamics in striated muscle,” can be requested by emailing “Triclosan is found in virtually everyone’s home and is pervasive in the environment,” said Isaac Pessah, professor and chair of the Department of Molecular Biosciences in the UC Davis School of Veterinary Medicine and the principal investigator for the study. “These findings provide strong evidence that the chemical is of concern to both human and environmental health.” Since its first use in hospitals, triclosan has been added to hand soaps, deodorants, mouthwashes, toothpaste, bedding, clothes, carpets, toys and trash bags. More than one million pounds are produced annually in the U.S., and the chemical is found in waterways, aquatic organisms and human urine, blood and breast milk. While ACI, formerly the Soap and Detergent Association, claims that university researchers “overdosed” test subjects (mice and fish) in their experiments, university researchers say the doses were “similar to those that people and animals may be exposed to during everyday life.” The UC Davis-led research team previously found triclosan disruptive of reproductive hormone activity and cell signaling in the brain. In the new research, the universities found that triclosan impairs heart and skeletal muscle contractions in living animals. Anesthetized mice had up to a 25 percent reduction in heart function measures within 20 minutes of being exposed to the chemical. “The effects of triclosan on cardiac function were really dramatic, said Nipavan Chiamvimonvat , UC Davis professor of cardiovascular medicine and study co-author. “Although triclosan is not regulated as a drug, this compound acts like a potent cardiac depressant in our models.” In addition, the mice have less grip strength for up to one hour after a single dose of triclosan. Grip strength is a widely used measure for mouse limb strength in these investigations. Reduced swimming activity was noted in fish exposed to the chemical. “We were surprised by the large degree to which muscle activity was impaired in very different organisms and in both cardiac and skeletal muscle” said Bruce Hammock, professor at UC Davis’s Department of Entomology and a co-author of the study. “You can imagine in animals that depend so totally on muscle activity that even a 10 percent reduction in ability can make a real difference in their survival.” The researchers acknowledge that more study will be required to translate the results from animal models to humans, but they suspect that triclosan could have large effects on animal and human health at current levels of exposure. Chiamvimonvat, the cardiovascular expert, says for people with underlying heart conditions triclosan “could have significant effects because it is so widely used.” “However, with additional studies, it would be difficult for a physician to distinguish between natural disease progression and an environmental factor such as triclosan,” said Chiamvimonvat. “We have shown that triclosan potently impairs muscle function by interfering with signaling between two proteins that are of fundamental importance to life,” said Pessah. “Regulatory agencies should definitely be reconsidering whether it should be allowed in consumer products.” Hammock called for a dramatic reduction in the use of triclosan, saying it may be useful in some instances but it could be more harmful than helpful as a “ubiquitous ‘value added” marketing factor.” Other authors of the study were Gennady Cherednichenko, Rui Zhang, Erika Fritsch, Wei Feng and Genaro Barrientos of the UC Davis School of Veterinary Medicine; Roger Bannister and Kurt Beam of the University of Colorado Denver-Anschutz Medical Campus; Valeriy Timofeyev and Ning Li of the UC Davis Division of Cardiovascular Medicine; and Nils Schebb of the UC Davis Department of Entomology. Beyond Pesticides, which encourages consumers not to purchase products containing triclosan, says some major companies are already “quietly removing” the chemical from products. “Colgate-Palmolive, makers of SoftSoap and GlaxoSmithKline, makers of Aquafresh and Sensodyne toothpastes, have reformulated some of their products to exclude triclosan, according to media reports. Others, including Johnson & Johnson, L’Oreal, The Body Shop, and Staples, have started phasing it out of products,” the BP group says. In its statement blasting the new study, ACE says both the European Commission’s Scientific Committee on Consumer Safety in 2011 and Health Canada/Environment Canada in 2012 have reaffirmed the safety of triclosan. The EC found that “use of triclosan at a maximum concentration of 0.3 percent in toothpastes, hand soaps/shower gels and deodorant sticks is considered safe.” “Antibacterial soaps are used as part of common sense hygiene routines in homes, hospitals, doctors’ offices, day care centers, and countless other office and institutional settings,” says ACI’s Richard Sedlak. He says they’ve “stood the test of time.” Beyond Pesticides claims Canada is “set to declare triclosan toxic to the environment, an action which triggers a process to find ways to curtail a chemical’s use including a possible ban in personal care products.” It says the U.S. Food and Drug Administration (FDA) claims that concerns about repetitive daily exposure to triclosan are valid. Food Safety News could not confirm either of these claims. Triclosan’s role, if any, in promoting drug resistance was not addressed by the new study. However, triclosan is used to fight superbugs. Showers and baths with 2 percent triclosan are recommended regimens for the decolonization of patients whose skin is carrying methicillin-resistant Staphylococcus aureus (MRSA).