You may want to think twice before reaching for the hand sanitizer at the grocery store. There is now one more reason for people to break their love affair with antibacterial soaps, hand sanitizers, and cleaning products. Triclosan, a common ingredient in antibacterial products, weakens isolated muscle cells in the laboratory, as well as muscles in living fish and mice, at doses similar to those people and animals may be exposed to in everyday life.

Previous research suggests that triclosan may also act as an endocrine disrupter.

What surprised the researchers most was triclosan's ability to affect both heart and skeletal muscle in very different organisms.

In 2010, the FDA concluded that, except for its use in toothpaste for treating gingivitis (gum disease), triclosan provides no known health benefits to people: "At this time, the agency does not have evidence that triclosan in antibacterial soaps and body washes provides any benefit over washing with regular soap and water."

Yet triclosan continues to be found in products ranging from hand soaps, mouthwashes and deodorants to bedding, clothes, toys, carpeting and trash bags.

The study's three main findings:

  • In isolated heart and skeletal muscle tissue, triclosan inhibited muscular contraction within 10-20 minutes of exposure.
  • In mice, injected triclosan, at a concentration of 12.5 mg/kg body weight, reduced heart function by up to 25% in anesthetized mice and reduced grip strength of conscious mice by 18% for up to 60 minutes.
  • Triclosan exposure for seven days, at a concentration of 0.52 micromolar, significantly inhibited the swimming ability of fathead minnow larvae. Fathead minnows are a small fish often used to study the effect of aquatic pollutants.

What surprised the researchers from the University of California, Davis and the University of Colorado most was triclosan's ability to affect both heart and skeletal muscle in very different organisms.

A decrease of muscle activity comparable to that seen by the researchers might not be particularly noticeable in a healthy person. It certainly would be in a person with heart failure, whose heart is constantly under stress to provide sufficient blood flow to the rest of the body. And to creatures in the wild that depend on their muscles to avoid predators or capture prey, a 10 or 20% reduction in muscle function could make a real difference in their survival.

Back in 1998, annual triclosan production in the U.S. was estimated at one million pounds. There's no indication that this number has gone down. Enough triclosan has built up that it's now detectable in human milk, blood and urine and as a pollutant in many waterways.

Triclosan is chemically related to polychlorinated biphenyls (PCBs), pollutants that persist in the environment for a very long time without breaking down. The triclosan that you're flushing down the drain may not be a very large amount, but imagine millions or billions of people doing the same and you've got one big pile of--potentially toxic waste.

It's true that tests of chemicals showing harm to animals don't always mean that these chemicals cause harm in humans. But with no known benefit and a possibility of harm, why would people even consider buying triclosan-containing products?

It might be time to pay a little closer attention to the ingredient listings of soaps, cleaners and personal care products.

An article on the study was published online by the Proceedings of the National Academy of Sciences (PNAS).