An antibacterial agent used in common household items such as soaps, toothpaste, processed food, and clothing represents a potential health risk to human hormone action, says a new study co-authored by a University of Victoria researcher.

The study, published online this week in Aquatic Toxicology, examined the effects of the antibacterial agent known as triclosan on the development, or metamorphosis, of tadpoles into frogs. The study showed that when tadpoles are exposed to levels of triclosan commonly found in the environment, frog metamorphosis that relies on thyroid hormones was significantly disrupted.

Triclosan is of particular concern to toxicologists because it is structurally similar to thyroid hormones, which play a crucial role in early human development.

“Thyroid hormones and the mechanisms by which they affect cells are highly conserved from frog to mammal,”
said Dr. Caren Helbing, a UVic molecular biologist.

“It's highly likely that what affects frogs could affect mammals, even humans.?

Triclosan is used in a wide variety of products, including clothing, food, personal care products, and some plastics to make them more bacteria-resistant. It is present in municipal effluents, is persistent in the environment, and accumulates up the food chain.

The study found that as little as one-millionth of a gram per litre of triclosan interferes with thyroid hormones and their ability to direct the genes responsible for frog metamorphosis. This is the same concentration of triclosan found in 85 waterways tested across the U.S. in another, recent study.

Triclosan has also been detected in human breast milk, notes Helbing.

“These levels are in the general range of what we tested, so triclosan may be having an impact on babies during a vulnerable time when thyroid hormones are important in their development.?

Helbing hopes this study will spur further research into how low doses of triclosan might be affecting human and wildlife health.

“Given that there's already concern over the indiscriminate use of this product and the promotion of resistant bacteria, it would seem prudent to limit its use to those products where it's really needed.?

To see a copy of the paper visit www.sciencedirect.com and click on ?Articles in Press.?

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