Urinary phthalate metabolite concentrations among pregnant women in Northern Puerto Rico: Distribution, temporal variability, and predictors
Introduction
Endocrine disrupting chemicals (EDCs) are exogenous compounds with the potential to mimic or interfere with the normal actions of hormones in humans and animals (Tabb and Blumberg, 2006). The widespread and increasing use of these compounds in chemical production and documented associations with a host of adverse health endpoints have spurred growing scientific concerns and public debate. One such group of EDCs are phthalate esters or phthalates. Phthalates are commonly utilized worldwide as additives providing flexibility to otherwise rigid plastics (Schettler, 2006). Downstream applications of plastics containing high molecular weight phthalates, such as di-2-ethylhexyl phthalate (DEHP) and benzylbutyl phthalate (BBzP), include building materials (e.g. vinyl flooring), furnishings, medical devices, packaging, etc.; contamination is also found in a variety of food products (NRC (National Research Council), 2008, Schecter et al., 2013, Schettler, 2006, Wormuth et al., 2006). Low molecular weight phthalates, such as dibutyl phthalate (DBP) and diethyl phthalate (DEP), are also used as plasticizers in a variety of applications, as solvents in many personal care products, as coatings for medications, and other uses (Duty et al., 2005, Hauser et al., 2004, NRC (National Research Council), 2008, Sathyanarayana et al., 2008).
Phthalates are continuously released into the environment as a result of the absence of covalent bonding with the products in which they are used, and the rate of release can be altered by factors such as temperature (NRC, 2008). Exposure in humans can occur through various routes, including ingestion of foods contaminated during processing and packaging, inhalation, and dermal absorption (Adibi et al., 2003, Rudel et al., 2003). Multiple studies worldwide, as well as in the United States, have demonstrated widespread exposure to phthalates, where detectable urinary concentrations of phthalate metabolites have been measured in nearly 100% of individuals (CDC (Centers for Disease Control), 2012, Jonsson et al., 2005, Kolossa-Gehring et al., 2012). While exposure to phthalates has been commonly been reported within the general population, of particular concern is evidence of fetal exposure, where urinary levels of phthalate biomarkers have been detected in pregnant women around the world (Adibi et al., 2008, Berman et al., 2009, Casas et al., 2011, Huang et al., 2007, Irvin et al., 2010, Meeker et al., 2009, Philippat et al., 2012, Suzuki et al., 2010, Swan et al., 2005, Woodruff et al., 2011, Ye et al., 2008, Zeman et al., 2013).
In addition to the normal day to day dietary and product usage patterns, which may differ from other populations, Puerto Ricans may have higher than average phthalate exposures due to extensive environmental contamination of groundwater, especially along the North Coast karst aquifer system (Padilla et al., 2011). Multiple hazardous waste sites in Puerto Rico, including four National Priority List sites: Barceloneta Landfill, Vega Baja Solid Waste Disposal, Scorpio Recycling, and Pesticide Warehouse III, have reported phthalate contamination (EPA (Environmental Protection Agency), 2013, Padilla et al., 2011). Phthalate exposure levels in humans and related sources are not well documented in Puerto Rico, although there is evidence of widespread endocrine disruption as Puerto Rico has had the highest rates of premature thelarche ever recorded (Larriuz-Serrano et al., 2001).
In light of potential health impacts of phthalate exposure, targeted action for elimination of exposure sources may be warranted, especially for sensitive populations like pregnant women. Given the wide range of products and environmental sources containing phthalate esters, variations in population geography, dietary practices, and lifestyle factors, designing effective strategies to reduce exposure will require culturally relevant information. Due to the lack of understanding on exposure to EDCs, including phthalates, in Puerto Rico, the objective of this study was to determine levels and predictors of urinary biomarkers of phthalates at multiple times during pregnancy of women living in the Northern karst area of Puerto Rico. Data on temporal variability in phthalate biomarker concentrations in pregnancy were also investigated to inform our ongoing epidemiology study on environmental risk factors for preterm birth, as Puerto Rico has the highest preterm birth rates of all US states and territories and phthalate exposure is a potential risk factor we aim to explore which has been previously associated with preterm birth (Blencowe et al., 2012, Meeker et al., 2009).
Section snippets
Study participants
The data presented were collected from pregnant women participating in the Puerto Rico Testsite for Exploring Contamination Threats (PROTECT) project, an ongoing prospective birth cohort in the Northern karst region of Puerto Rico, which is designed to evaluate the potential relationship between environmental toxicants and risk of preterm delivery. Study participants were recruited around 14 ± 2 weeks of gestation at seven prenatal clinics and hospitals throughout Northern Puerto Rico during
Results
Statistical analysis was conducted for both unadjusted and specific gravity-adjusted phthalate metabolite concentrations on a total of 373 urine samples from 139 women, and results were highly consistent between the two approaches. Of the total number of participants, 133 (95.7%) had two or more repeat urine samples for analysis. Demographic characteristics of our study sample are shown in Table 1. Most women in our study were highly educated, employed, married or in a domestic partnership, and
Discussion
In the present study, we found evidence for widespread exposure to phthalates among pregnant women living on the Northern coast of Puerto Rico, where all measured phthalate metabolites were detected for nearly 100% of the urine samples. Concentrations for a majority of the metabolites measured were higher in the Puerto Rican participants when compared to women of reproductive age in the mainland US population, especially MEHP which had a median and geometric mean concentrations that were more
Conclusions
To our knowledge this is the first study to report concentrations, temporal variability, and predictors of phthalate biomarkers among pregnant women in Puerto Rico. Concentrations for a majority of the metabolites measured were somewhat higher in the Puerto Rican participants when compared to women of reproductive age in the mainland US population. We found positive associations between MEP concentrations and self-reported use of perfume and colored cosmetics. Additionally, we observed
Acknowledgments
The project described was supported by P42ES017198 and P30ES017885 from the National Institute of Environmental Health Sciences (NIEHS). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute of Environmental Health Sciences, the National Institutes of Health, or the Centers for Disease Control and Prevention. The authors declare no competing financial interests. We gratefully acknowledge Manori Silva, Ella
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