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24 juin 2012 7 24 /06 /juin /2012 15:55
Journal of Exposure Science and Environmental Epidemiology (2012) 22, 376–385; doi:10.1038/jes.2012.7; published online 22 February 2012

Urinary phthalate metabolites and their biotransformation products: predictors and temporal variability among men and women

John D Meeker1, Antonia M Calafat2 and Russ Hauser3,4

1Department of Environmental Health Sciences, University of Michigan, Ann Arbor, Michigan, USA
2Centers for Disease and Control and Prevention, Atlanta, Georgia, USA
3Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, USA
4Vincent Memorial Obstetrics and Gynecology Service, Andrology Laboratory and In Vitro Fertilization Unit, Massachusetts General Hospital, Boston, Massachusetts, USA
Correspondence: Dr. John D. Meeker, Department of Environmental Health Sciences, University of Michigan School of Public Health, 6635 SPH Tower, 109 S. Observatory Street, Ann Arbor, MI 48109, USA. Tel.: +1 734 764 7184. Fax: +1 734 936 7283. E-mail: meekerj@umich.edu

Received 6 July 2011; Accepted 7 October 2011
Advance online publication 22 February 2012

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Abstract
Most epidemiology studies investigating the potential adverse health effects in relation to phthalates measure the urinary concentration of the free plus glucuronidated species of phthalate metabolites (i.e., total concentration) to estimate exposure. However, the free species may represent the biologically relevant dose. In this study, we collected 943 urine samples from 112 men and 157 women and assessed the between- and within-person variability and predictors of (1) the free and total urinary concentrations of phthalate metabolites, and (2) the percentage of free phthalate metabolites (a potential phenotypic indicator of individual susceptibility). We also explored the proportion of urinary di-(2-ethylhexyl) phthalate (DEHP) metabolites contributed to by the bioactive mono-2-ethylhexyl phthalate (MEHP), considered a possible indicator of susceptibility to phthalate exposure. The percentage of phthalate metabolites present in the free form was less stable over time than the total metabolite concentration, and, therefore, it is not likely a useful indicator of metabolic susceptibility. Thus, the added costs and effort involved in the measurement of free in addition to total metabolite concentrations in large-scale studies may not be justified. Conversely, the proportion of DEHP metabolites contributed to by MEHP was more stable within individuals over time and may be a promising indicator of susceptibility if time of day of sample collection is carefully considered.

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