| Reproducibility of Urinary Phthalate Metabolites in First Morning Urine Samples Jane A. Hoppin,1 John W. Brock,2 Barbara J. Davis,3 and Donna D. Baird1 1Epidemiology Branch, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA; 2Centers for Disease Control and Prevention, Atlanta, Georgia, USA; 3Laboratory of Women's Health, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA Abstract
Phthalates are ubiquitous in our modern environment because of their use in plastics and cosmetic products. Phthalate monoesters--primarily monoethylhexyl phthalate and monobutyl phthalate--are reproductive and developmental toxicants in animals. Accurate measures of phthalate exposure are needed to assess their human health effects. Phthalate monoesters have a biologic half-life of approximately 12 hr, and little is known about the temporal variability and daily reproducibility of urinary measures in humans. To explore these aspects, we measured seven phthalate monoesters and creatinine concentration in two consecutive first-morning urine specimens from 46 African-American women, ages 35-49 years, residing in the Washington, DC, area in 1996-1997. We measured phthalate monoesters using high-pressure liquid chromatography followed by tandem mass spectrometry on a triple quadrupole instrument using atmospheric pressure chemical ionization. We detected four phthalate monoesters in all subjects, with median levels of 31 ng/mL for monobenzyl phthalate (mBzP) , 53 ng/mL for monobutyl phthalate (mBP) , 211 ng/mL for monoethyl phthalate (mEP) , and 7.3 ng/mL for monoethylhexyl phthalate (mEHP) . These were similar to concentrations reported for other populations using spot urine specimens. Phthalate levels did not differ between the two sampling days. The Pearson correlation coefficient between the concentrations on the 2 days was 0.8 for mBP, 0.7 for mEHP, 0.6 for mEP, and 0.5 for mBzP. These results suggest that even with the short half-lives of phthalates, women's patterns of exposure may be sufficiently stable to assign an exposure level based on a single first morning void urine measurement. Key words: biologic markers, environmental exposure, phthalates, reliability, urine, women's health. Environ Health Perspect 110:515-518 (2002) . [Online 3 April 2002] http://ehpnet1.niehs.nih.gov/docs/2002/110p515-518hoppin/ abstract.html Address correspondence to J.A. Hoppin, Epidemiology Branch, MD A3-05, NIEHS, PO Box 12233, Research Triangle Park, NC 27709-2233. Telephone: (919) 541-7622. Fax: (919) 541-2511. E-mail: hoppin1@niehs.nih.gov We thank M. Silva for chemical analyses, T. Gabriel and C. Dodson for sample processing, D. Shore and R. Ulmer for programming support, and E. Gunter for providing urinary creatinine analysis. M. Longnecker and J. Daniels provided helpful comments on a draft version of the manuscript. Received 15 October 2001 ; accepted 19 November 2001.
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