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Hand-soap chemical may impair muscle function

Call for regulators to reconsider use of triclosan

Jo Carlowe

Tuesday, 14 August 2012

The antibacterial chemical triclosan widely used in hand soaps hinders muscle contractions at a cellular level, researchers have found.

According to the findings published online in the Proceedings of the National Academy of Sciences of the United States of America, the chemical slows swimming in fish and reduces muscular strength in mice.

Isaac Pessah, professor and chair of the Department of Molecular Biosciences, at the University of California, School of Veterinary Medicine, principal investigator of the study, said the findings are of concern ‘to both human and environmental health’.

“Triclosan is found in virtually everyone's home and is pervasive in the environment," he said

Triclosan is commonly found in antibacterial personal-care products such as hand soaps, deodorants, mouthwashes, toothpaste, bedding, clothes, carpets, toys and bin bags.

The investigators performed several experiments to evaluate the effects of triclosan on muscle activity, 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 fibres to contract. Specifically, the team evaluated the effects of triclosan on molecular channels in muscle cells that control the flow of calcium ions, creating muscle contractions. Normally, electrical stimulation ("excitation") of isolated muscle fibres under experimental conditions evokes a muscle contraction, a phenomenon known as "excitation-contraction coupling" (ECC), the fundamental basis of any muscle movement, including heartbeats. But in the presence of triclosan, the normal communication between two proteins that function as calcium channels was impaired, causing skeletal and cardiac muscle failure.

The team also found that triclosan impairs heart and skeletal muscle contractility in living animals. Anesthetised mice had up to a 25% reduction in heart function measures within 20 minutes of exposure to the chemical.

"The effects of triclosan on cardiac function were really dramatic," said Nipavan Chiamvimonvat, professor of cardiovascular medicine at UC Davis and a 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 had an 18% reduction in grip strength for up to 60 minutes after being given 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 for studying the potential impacts of aquatic pollutants. Those exposed to triclosan in the water for seven days had significantly reduced swimming activity compared to controls.

Chiamvimonvat cautioned that translating results from animal models to humans is a large step. However, given the results, the authors called on regulatory agencies to reconsider whether Triclosan should be allowed in consumer products.

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