Phthalates Biomarker Identification and Exposure Estimates in a Population of Pregnant Women

ABSTRACT

Phthalates are known reproductive and developmental toxicants in experimental animals. However, in humans, there are few data on the exposure of pregnant women that can be used to assess the potential developmental exposure experienced by the fetus. We measured several phthalate metabolites in maternal urine, maternal serum, and cord serum samples collected at the time of delivery from 150 pregnant women from central New Jersey. The urinary concentrations of most metabolites were comparable to or less than among the U.S. general population, except for mono(2-ethylhexyl) phthalate (MEHP), mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), and mono(2-ethyl-5-oxohexyl) phthalate (MEOHP), three metabolites of di(2-ethylhexyl) phthalate (DEHP). The median urinary concentrations of MEHHP (109 μ g/l) and MEOHP (95.1 μ g/l) were more than 5 times their population-based concentrations, whereas the median urinary concentration of MEHP was more than 20 times higher. High concentration of MEHP may indicate a recent exposure to the parent chemical DEHP in the hospital shortly before the collection of the samples. Calculation of daily intakes using the urinary biomarker data reveals that none of the pregnant women tested had integrated exposures to DEHP greater than the Agency for Toxic Substances and Disease Registry's minimal risk levels (MRLs chronic 60, intermediate 100 μ g/kg/day). No abnormal birth outcomes (e.g., birth weight, Apgar Score, and gestational age) were noted in those newborns whose mothers had relatively greater exposure to DEHP during the perinatal period than others in this study. Significantly greater concentrations and detection frequencies in maternal urine than in maternal serum and cord serum suggest that the urinary concentrations of the phthalate metabolites may be more reliable biomarkers of exposure than their concentrations in other biological specimens.

Key Words:

• phthalates
• metabolites
• daily intake
• risk assessment
• women
• children

ACKNOWLEDGMENTS

We thank Dr. Jack Reidy, Jim Preau, and Arnetra Herbert for their assistance in the phthalate analytical measurements. We also thank Dr. Kenneth R. Reuhl in the Department of Pharmacology and Toxicology, Rutgers University/UMDNJ, Piscataway, NJ, for his assistance. This work was supported by grants from New Jersey Department of Environmental Protection (DEP SR02-038, SR04-058, SR05-042) and the NIEHS P30ES005022 and NIEHS 5T32ES07148.

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 or the New Jersey Department of Environmental Protection.

Notes

^a All values expressed as: mean concentration/standard deviation/subject number.

^b Significant differences in urinary concentrations between plastic product users and non-users (p < 0.05).

*Geometric mean not calculated because detection of frequency < 60%.