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Janet Gray, Ph.D.
Janet Gray, Ph.D.

As author of our 2008 and 2010 State of the Evidence reports, Dr. Gray drives the science behind all our work.

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Triclosan and Triclocarban

CATEGORY*: Not classified

FOUND IN: Antibacterial personal care products, antimicrobial household products

THE GIST: Triclosan and triclocarban are antibacterial chemicals and known endocrine disruptors found in cosmetics, soap, deodorant, sponges, toothpaste, cutting boards, shoes, towels and clothes. A limited body of research has explored how triclosan affects breast cancer cells. Evidence does suggest that triclosan can affect aquatic wildlife and the hormonal systems of mice. It may impact male and female hormones like testosterone and estrogen, and may also affect thyroid systems, which regulate weight and metabolism.

State of the Evidence on Triclosan and Triclocarban

Triclosan and triclocarban are antimicrobial agents that have been used broadly in a wide range of personal care, household and industrial products over the past 40 years (Dann, 2011). In its chemical structure triclosan has similarities both to thyroid hormone (T4) and to several known endocrine disruptors, including polychlorinated bisphenyls (PCBs), diethylstilbestrol (DES) and bisphenol A (BPA); triclocarban has chemical properties similar to those of several pesticides and pharmaceuticals (Ahn, 2008).


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Both are found in freshwater samples, especially in lakes and downstream from wastewater treatment plants, in concentrations known to be harmful to wildlife (Brausch, 2011; Venkatesan, 2012).

In a study of urine samples from U.S. adults as part of the Center for Disease Control and Prevention’s NHANES study, 75 percent of samples were found to have significant levels of triclosan and its metabolites. Higher levels were found in young adults and more affluent adults (Calafat, 2008a). A parallel NHANES study examining chemical levels in pregnant women found measurable levels of triclosan in 87 percent of urine samples examined (Woodruff, 2011). In a smaller study of U.S. adult samples, triclocarban and its metabolites were detected in one-third of urine and one-half of blood serum samples that were tested (Ye, 2011). Human autopsy analysis reveals that triclosan bioaccumulates in liver and adipose (fat) tissue, but not brain tissue, the three tissue types examined (Geens, 2012).

Although there has been very little work examining the direct effects of either triclosan or triclocarban on mammary system development or risk for developing breast cancer, considerable research demonstrates that these two compounds exert effects on hormonal systems in ways similar to established mechanisms for perturbing normal breast development and health. Depending on the concentration of the chemical tested and the model system used, triclosan and triclocarban exert a complex combination of estrogenic and antiestrogenic, and androgenic and antiandrogenic effects, all regulated at least in part through interactions with the estrogen receptor and androgen receptor of target cells (Ahn, 2008; Christen, 2010; Dann, 2010; Gee, 2008; Stoker, 2010).

One study examined the effects of triclosan on proliferation rates of cultured human breast cancer cells. Even very low doses of triclosan were estrogen-like in enhancing proliferation rates of these cells, yet in combination with low doses of the natural estrogen estradiol, triclosan was antiestrogenic in that it reduced the estradiol-induced increase in cell growth and proliferation (Henry, 2011). At higher, but still environmentally relevant levels, triclosan was toxic to the cells.

In addition to its effects exerted through the estrogen and androgen receptor systems, triclosan has been shown to alter levels of thyroid hormone (T4) in pubertal rats (Stoker, 2010; Zorrilla, 2009). Treatment of mother rats with triclosan during the period of lactation led to a sustained three-week decrease in their thyroid hormone levels. Pups, however, only had suppressed T4 levels for the first few days of suckling, with normal levels being recorded later in the period despite continued exposure to triclosan through the mothers’ milk (Paul, 2010).

*For chemicals that have been shown to be carcinogens, we provide classifications from two authoritative bodies: the International Agency for Research on Cancer (IARC, an international body) and the National Toxicology Program (NTP, a division of the U.S. Department of Health and Human Services). We have categorized endocrine-disrupting compounds where the body of peer-reviewed research indicates a strong foundation for doing so.