Critical analysis of endocrine disruptive activity of triclosan and its relevance to human exposure through the use of personal care products

Abstract

This review examines the mammalian and human literature pertaining to the potential endocrine disruptive effects of triclosan (TCS). Dietary exposure to TCS consistently produces a dose-dependent decrease in serum thyroxine (T4) in rats without any consistent change in TSH or triiodothyronine (T3). Human studies reveal no evidence that the TCS exposure through personal care product use affects the thyroid system. TCS binds to both androgen and estrogen receptors in vitro with low affinity and evokes diverse responses (e.g., agonist, antagonist, or none) in steroid receptor transfected cell-based reporter assays. Two of three studies in rats have failed to show that TCS exposure suppresses male reproductive function in vivo. Three of four studies have failed to show that TCS possesses estrogenic (or uterotrophic) activity in rats. However, two studies reported that, while TCS lacks estrogenic activity, it can amplify the action of estrogen in vivo. The in vitro, in vivo, and epidemiologic studies reviewed herein show little evidence that TCS adversely affects gestation or postpartum development of offspring. Furthermore, previously reported toxicity testing in a variety of mammalian species shows little evidence that TCS adversely affects thyroid function, male and female reproductive function, gestation, or postpartum development of offspring. Finally, doses of TCS reported to produce hypothyroxinemia, and occasional effects on male and female reproduction, gestation, and offspring in animal studies are several orders of magnitude greater than the estimated exposure levels of TCS in humans. Overall, little evidence exists that TCS exposure through personal care product use presents a risk of endocrine disruptive adverse health effects in humans.

Keywords:

• androgen receptor
• estradiol
• estrogen receptor
• female reproduction
• gestation
• Leydig cells
• male reproduction
• postpartum development
• testosterone
• thyroid
• thyroxine
• triiodothyronine
• TSH
• uterotrophic effects

Acknowledgments

The author wishes to acknowledge Dr. Robinan Gentry of Environ International Corporation for assistance in proofreading and review of this manuscript.

Declaration of interest

Raphael J. Witorsch is Professor Emeritus at Virginia Commonwealth University. The work was funded by the Colgate-Palmolive Company who compensated the author for preparation of the review. Colgate-Palmolive Company was given the opportunity to review and comment on the paper. Dr. Witorsch has also served as a consultant to the Personal Care Products Council. This review represents the opinions of the author and not necessarily those of Colgate-Palmolive Company or Personal Care Products Council.

Notes

¹In this study TCS is dissolved in phosphate buffered saline. This is in contrast to other studies in which TCS was administered through oral gavage administration where corn oil was the vehicle (Zorrilla et al. 2009; Paul et al. 2010a, 2010b, 2012; Stoker et al. 2010, Axelstad et al. 2013).

²On request from theEuropean Commission, Question No EFSA-Q-2012-00760,adopted on 28 February 2013.