By Sandra McCulloch

VICTORIA, CANADA -- Whether you're washing your hands or the kitchen countertops, it's best for your family's health and the environment to pass up antibacterial products in favour of plain soap and water, a University of Victoria researcher has found.

UVic molecular biologist Caren Helbing found while triclosan -- common in soaps, clothing, toys and other items having antibacterial properties -- isn't lethal in small quantities, it can potentially affect the human thyroid gland. The thyroid plays a role in development, body temperature and metabolism.

"For most things, regular soap is just fine. In terms of children's products, they shouldn't have triclosan in them at all," Helbing said in an interview.

Helbing's research, published last week in the online journal Aquatic Toxicology, found triclosan to be harmful in the development of frogs and potentially humans. At the molecular level, the chemical compound is similar to vertibrates' thyroid hormone. Helbing found triclosan at levels found in the environment disrupted a tadpole's transition into a frog.

"Frogs serve as a very sensitive sentinel species for chemicals that can actually disrupt thyroid hormone action," said Helbing. "Triclosan at levels measured in our waterways can actually affect how thyroid hormones works in frogs."

The chemical compound is man-made for the purpose of killing bacteria and is showing up in more consumer products. Easy-clean items marketed as containing "Microban" contain triclosan, said Helbing. But Helbing said triclosan is not necessary to clean up most household spills, and other scientists agree.

"When you ask a qualified microbiologist, they'll tell you that it's being overdone and there's probably a greater chance of creating bacterial resistance than preventing problems," said Joe Schwarcz, director of McGill University's Office for Science and Society. "Washing with soap and water is enough, except in a hospital environment ... You don't want to use a jackhammer to kill an ant when stepping on it will do.

"The reason why the triclosan story is interesting is it's so pervasive -- it's in so many products. Even (though) the risk (of ill effects) is small, the exposure is too large."

Helbing agrees the prevalence of triclosan in the environment can make the fight against antibiotic-resistant illnesses more difficult.

It can also affect normal human development: "There are a lot of different processes in the body that can be affected."

In March, the Canadian Paediatric Society called for parents to stop buying antibacterial products, and instead use soap and water to wash toys, hands or household items.

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Germ Fighter Works As Endocrine Disrupter

By Janet Pelley

Triclosan, widely used in soaps and toothpastes for its ability to kill bacteria, has been found to hasten the transformation of tadpoles into adult frogs. The new research, published online September 29 in Aquatic Toxicology, is the first to show that triclosan can act as an endocrine disrupter at concentrations found in North American streams.

Although sewage treatment plants remove most of the triclosan washed down the drain, the chemical makes its way into U.S. streams at readily detectable levels. More than 55% of streams examined in 2002 had a median concentration of 0.14 parts per billion (ppb) (Environ. Sci. Technol. 2002, 36, 1201–1211).

Previous studies have shown that triclosan, which has a similar chemical structure to polybrominated diphenyl ethers and PCBs, bioaccumulates in fish and is present in human breast milk, according to Caren Helbing, who is a molecular biologist at the University of Victoria (Canada) and a coauthor of the study. Intrigued by triclosan’s structural similarity to thyroid hormones, which orchestrate growth and development in wildlife and humans, Helbing and her colleagues set out to determine whether triclosan could interfere with thyroid-hormone activity in frogs.

When the team exposed young bullfrog tadpoles—which do not yet produce thyroid hormones—to triclosan alone, they did not observe any significant changes. However, when the tadpoles were exposed to triclosan and thyroid hormones together, the scientists documented a mosaic of impacts.

The triclosan effects included significant weight loss and accelerated hind-limb development. Helbing and co-workers also detected elevated activity in the brain of genes linked with uncontrolled cell growth, and decreased gene activity in the tail fin. The data suggest that triclosan, at concentrations as low as 0.15 ppb, is capable of perturbing a fundamental hormone signaling mechanism that is nearly identical in frogs and humans, she says.

“This experimental design is very clever because [Helbing] looked at both the presence and absence of thyroid hormone,” says Tom Zoeller, an endocrinologist at the University of Massachusetts, Amherst. If Helbing had merely exposed the tadpoles to triclosan alone, she would have missed adverse effects on the thyroid system, he says. But because she added thyroid hormone along with triclosan, she could see that the triclosan made the thyroid hormone much more potent than it would have been under normal circumstances.

These results hint that triclosan does not mimic thyroid hormones but instead speeds up their impact, says Cathy Propper, an endocrinologist at Northern Arizona University. Although the mechanism is unknown, triclosan may be making protein receptors in the cell more sensitive to thyroid hormones, Zoeller speculates. Because thyroid-hormone signaling is essential for the development of the human brain and body, the new study raises red flags for human health, Zoeller says.

Current screening programs for endocrine disrupters, such as the protocols being considered by the U.S. EPA, might miss the effects observed by Helbing and her team, Zoeller says. Tests of contaminants might not be conducted in the presence of natural hormones, or animals might be tested at a stage of life when the targeted responses aren’t sensitive to thyroid hormones, he says. Triclosan producers declined to comment on this study for this story.

“The insidiousness of these compounds in the environment is that they don’t necessarily have a direct impact but can be inappropriately sensitizing or desensitizing animals to their own endocrine environment,” Propper says. The question to ask, she continues, is: “Do the antimicrobial gains you get from using triclosan outweigh both the risks to wildlife and the potential human health risks associated with it?”