Open for Discussion: Can Triclosan Be Harmful to Human Health?

By Kristin Harper  December 2015

Bowl of instant macaroni and cheese

Triclosan is a chemical added to many consumer products—including toothpaste, soaps, and deodorants—to kill microbes. Lately, triclosan has been receiving a lot of bad press because of worries about its potential health effects. There is a lot left to learn about this chemical, and its many uses in our society remain open for discussion.

It looks like a hormone...

There is no doubt that triclosan kills microbes, but its ability to mimic important molecules in our body, called hormones, and to interfere with their activities is less clear. Hormones are molecules that send essential messages between different parts of our body. Two hormones that triclosan is suspected to mimic are estrogen, which is produced by the ovaries and controls female sex characteristics; and thyroid hormones, which control metabolism—the conversion of food into energy. Triclosan is thought to mimic these hormones because of some general similarities in their structure. Many health concerns about triclosan center on this mimicry.

...But does it act like one?

Some research suggests that triclosan may not be a very good mimic of estrogen and thyroid hormones. Dave Furlow, a professor at the University of California (UC), Davis, and colleagues invented a cell line to test whether a compound interferes with thyroid hormone when it binds to one of these cells. When a chemical binds to the thyroid hormone receptor on these cells, they produce a chemical, called luciferase, that fireflies use to light up in the night (Fig. 1). Researchers can then measure the amount of light to determine how strongly a chemical binds to the receptor.

Scientists at the U.S. National Institutes of Health have found that triclosan binds to the thyroid hormone receptor only weakly, suggesting that triclosan does not interfere significantly with the thyroid hormones in our bodies.

Similarly, Michael Denison, another professor at UC, Davis, and colleagues have tested the effects of triclosan in ovarian cancer cells designed to produce luciferase when a compound binds to the estrogen receptor. In these studies, triclosan had no estrogen-like activity at all. These results suggest triclosan does not effectively mimic estrogen inside the body.

Reasons for concern

However, Rolf Halden, a professor at Arizona State University, is concerned that triclosan could interfere with molecules that bind to a receptor called the aryl hydrocarbon receptor (AhR). Normally, when this receptor is activated, it causes cells to undergo changes that are important in human development, but when some environmental pollutants bind to this receptor, it can lead to birth defects or cancer. Halden emphasizes that, although there is much we do not know about triclosan, we do know that this chemical is widespread in our environment as a result of pollution and we also know that it can be modified by our bodies to bind to the AhR receptor—which is concerning, given how important this receptor is for healthy development.

What do you think?

Because of its chemical structure and the way it is processed in our bodies, triclosan could interfere with our hormones. But how can we know for sure? Scientists are continually performing new studies to help answer this question, and you may find more answers by looking for reliable information online and discussing this topic with your friends and family. If you find interesting information, please feel free to share it with us by sending an e-mail to:

Also in the December 2015 Issue...

Lake Central High School, Saint John, Indiana

Make Safety Data Sheets a part of your chemistry instruction and teach your students how to assess hazards related to chemicals with this ChemMatters article. Feel free to print this article and to share it with your students and colleagues.