Parabens as Urinary Biomarkers of Exposure in Humans Xiaoyun Ye, Amber M. Bishop, John A. Reidy, Larry L. Needham, and Antonia M. Calafat Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, Georgia, USA Abstract Background: Parabens appear frequently as antimicrobial preservatives in cosmetic products, in pharmaceuticals, and in food and beverage processing. In vivo and in vitro studies have revealed weak estrogenic activity of some parabens. Widespread use has raised concerns about the potential human health risks associated with paraben exposure. Objectives: Assessing human exposure to parabens usually involves measuring in urine the conjugated or free species of parabens or their metabolites. In animals, parabens are mostly hydrolyzed to p-hydroxybenzoic acid and excreted in the urine as conjugates. Still, monitoring urinary concentrations of p-hydroxybenzoic acid is not necessarily the best way to assess exposure to parabens. p-Hydroxybenzoic acid is a nonspecific biomarker, and the varying estrogenic bioactivities of parabens require specific biomarkers. Therefore, we evaluated the use of free and conjugated parent parabens as new biomarkers for human exposure to these compounds. Results: We measured the urinary concentrations of methyl, ethyl, n-propyl, butyl (n- and iso-) , and benzyl parabens in a demographically diverse group of 100 anonymous adults. We detected methyl and n-propyl parabens at the highest median concentrations (43.9 ng/mL and 9.05 ng/mL, respectively) in nearly all (> 96%) of the samples. We also detected other parabens in more than half of the samples (ethyl, 58% ; butyl, 69%) . Most important, however, we found that parabens in urine appear predominantly in their conjugated forms. Conclusions: The results, demonstrating the presence of urinary conjugates of parabens in humans, suggest that such conjugated parabens could be used as exposure biomarkers. Additionally, the fact that conjugates appear to be the main urinary products of parabens may be important for risk assessment. Keywords: biomonitoring, conjugate, ethylparaben, metabolism, methylparaben, butylparaben, n-propylparaben, p-hydroxybenzoic acid esters, urine. Environ Health Perspect 114:1843–1846 (2006) . doi:10.1289/ehp.9413 available via http://dx.doi.org/ [Online 29 August 2006] Address correspondence to A.M. Calafat, Centers for Disease Control and Prevention, 4770 Buford Hwy, Mailstop MS F53, Atlanta, GA 30341 USA. Telephone: (770) 488-7891. Fax: (770) 488-4371. E-mail: Acalafat@cdc.gov This research was supported in part by an appointment (A.M.B.) to the Research Participation Program at the Centers for Disease Control and Prevention (CDC) , National Center for Environmental Health, Division of Laboratory Sciences, administered by the Oak Ridge Institute for Science and Education through an interagency agreement between the U.S. Department of Energy and CDC. The use of trade names is for identification only and does not constitute endorsement by the U.S. Department of Health and Human Services or the CDC. The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the CDC. The authors declare they have no competing financial interests. Received 12 June 2006 ; accepted 29 August 2006. The full version of this article is available for free in HTML or PDF formats. |