- Full (HTML) - Full (PDF) - Related EHP Articles - Purchase This Issue

Jennifer J. Adibi,¹ Robin M. Whyatt,² Paige L. Williams,³ Antonia M. Calafat,⁴ David Camann,⁵ Robert Herrick,¹ Heather Nelson,¹ Hari K. Bhat,² Frederica P. Perera,² Manori J. Silva,⁴ and Russ Hauser¹

¹Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, USA; ²Columbia Center for Children's Environmental Health, Mailman School of Public Health, Columbia University, New York, New York, USA; ³Department of Biostatistics, Harvard School of Public Health, Boston, Massachusetts, USA; ⁴National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, Georgia, USA; ⁵Southwest Research Institute, San Antonio, Texas, USA

Abstract
Background: Although urinary concentrations of phthalate metabolites are frequently used as biomarkers in epidemiologic studies, variability during pregnancy has not been characterized.

Methods: We measured phthalate metabolite concentrations in spot urine samples collected from 246 pregnant Dominican and African-American women. Twenty-eight women had repeat urine samples collected over a 6-week period. We also analyzed 48-hr personal air samples (n =96 women) and repeated indoor air samples (n =32 homes) for five phthalate diesters. Mixed-effects models were fit to evaluate reproducibility via intraclass correlation coefficients (ICC) . We evaluated the sensitivity and specificity of using a single specimen versus repeat samples to classify a woman's exposure in the low or high category.

Results: Phthalates were detected in 85–100% of air and urine samples. ICCs for the unadjusted urinary metabolite concentrations ranged from 0.30 for mono-ethyl phthalate to 0.66 for monobenzyl phthalate. For indoor air, ICCs ranged from 0.48 [di-2-ethylhexyl phthalate (DEHP) ] to 0.83 [butylbenzyl phthalate (BBzP) ]. Air levels of phthalate diesters correlated with their respective urinary metabolite concentrations for BBzP (r = 0.71) , di-isobutyl phthalate (r = 0.44) , and diethyl phthalate (DEP ; r = 0.39) . In women sampled late in pregnancy, specific gravity appeared to be more effective than creatinine in adjusting for urine dilution.

Conclusions: Urinary concentrations of DEP and DEHP metabolites in pregnant women showed lower reproducibility than metabolites for di-n-butyl phthalate and BBzP. A single indoor air sample may be sufficient to characterize phthalate exposure in the home, whereas urinary phthalate biomarkers should be sampled longitudinally during pregnancy to minimize exposure misclassification.

Key words: creatinine, indoor air, personal air, phthalates, pregnancy, specific gravity, urinary metabolites, variability. Environ Health Perspect 116:467–473 (2008) . doi:10.1289/ehp.10749 available via http://dx.doi.org/ [Online 15 January 2008]

Address correspondence to R.M. Whyatt, Department of Environmental Health Sciences, Joseph L. Mailman School of Public Health, Columbia University, 60 Haven Ave., B-109, New York, NY 10032 USA. Telephone: (646) 459-9609. Fax: (646) 459-9610. E-mail: rmw5@columbia.edu

We thank L. Hoepner, M. Odlum, A. Reyes, D. Holmes, and others on the CCCEH research staff for their tremendous efforts in all aspects of subject recruitment, sample and data collection, and processing. We also thank J. Reidy, J. Preau, and E. Samandar of the CDC for the phthalate metabolite analyses.

This research received support from grants R01 ES013543, P01 ES009600, P01 00002, and R01 ES 008977 from the National Institute of Environmental Health Sciences, and grant R827027 from the U.S. Environmental Protection Agency. The Harvard Education and Research Center for Occupational Safety and Health (T42 OH008416) funded doctoral training for J.J.A.

The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the Centers for Disease Control and Prevention.

The authors declare they have no competing financial interests.

Received 8 August 2007 ; accepted 14 January 2008.