New Study Finds That Triclosan Exposure Impacts Thyroid Hormones

(Beyond Pesticides, December 11, 2008)

In a recent study, researchers find that triclosan, the antibacterial agent found in many consumer products including soaps, toothpaste, cosmetics, counter tops and toys, alters thyroid function in male rats. These effects are observed at concentrations that may be used in consumer products and highlight the growing threat consumers face from this hazardous and ubiquitous chemical.

The study, entitled, “The effects of triclosan on puberty and thyroid hormones in male wistar rats,” was reviewed by the National Health and Environmental Effects Research Laboratory, the U.S. Environmental Protection Agency (EPA) and approved for publication in Toxicological Sciences. Researchers measured blood concentrations of testosterone and several other types of hormones and weighed a variety of organs that are essential for rat development and puberty, including the pituitary gland, the testes, the prostate gland and the liver of male rat pups fed an oral dose of triclosan for 31 days. The purpose of the experiment was to determine what effects triclosan would have on concentrations of thyroid hormones and the onset of puberty.

Results show a dramatic decrease in the thyroid hormone -thyroxine in rats exposed to increasing concentrations of triclosan, as well as significant increases in liver weights. This thyroid hormone is critical for normal development and to a properly functioning metabolism. When the thyroid produces lower than normal amounts of hormones, hypothyroidism occurs and this condition can lead to obesity, goiter, infertility, neurological problems and other serious concerns. Hypothyroidism during early development can change reproductive tract development, hormone concentrations and sexual maturation, including puberty onset. It is unclear whether triclosan acts directly on the thyroid gland to interfere with hormone production. Enlarged livers, observed in the exposed rats, may indicate excessive stress on the liver to remove triclosan from the body. Stressed livers enlarge to accommodate the higher production of the enzymes needed to detoxify substances.

Triclosan is found in a variety of household products and has been detected in human blood, urine and even breast milk. This study’s findings raise further concern for adverse impacts on humans. Although this study used rats, the similarities in how the thyroid systems between rats and humans function raises concerns as to whether people could share the same physiological fate. Conversely, it takes a far greater dose of a chemical to alter a rat’s biology than it would to change a human’s; so although the concentrations evaluated in this study were higher than normal human exposure, it is possible that the low doses that humans are currently exposed to are enough to cause similar problems.

Triclosan’s association with hormone disruption has been documented in other studies and has also been observed in amphibians. In a recent risk assessment conducted by the EPA for the reregistration of triclosan, the agency, after reviewing this study and others, agreed that there is “evidence that triclosan disrupts thyroid hormone homeostasis and interacts with the androgen and estrogen receptors.”

In comments submitted to EPA in July 2008 by Beyond Pesticides, Food and Water Watch, Greenpeace US, Natural Resources Defense Council, Sierra Club and dozens of public health and environmental groups from the U.S. and Canada, the agency was urged to use its authority to cancel the non-medical uses of the antibacterial chemical triclosan in order to protect human health and the environment. However, despite these comments and the mounting evidence against triclosan’s safety and efficacy, the agency approved triclosan and triclosan-registered products for reregistration in September. The Reregistration Eligibility Decision (RED) document is open for public comment until December 29, 2008.

TAKE ACTION: Let EPA know that it is not doing all it could to protect public health and the environment from the serious and long-lasting impacts of the continued and unnecessary use of triclosan. Submit your comments at www. using docket number ID number EPA-HQ-OPP-2007-0513 no later than December 29, 2008. Follow the on-line instructions for submitting comments.

You can also send your comments via mail to the Office of Pesticide Programs (OPP) Regulatory Public Docket (7502P), Environmental Protection Agency, 1200 Pennsylvania Ave., NW., Washington, DC 20460-0001.

Source: Environmental Health News