Disparities in Adverse Environmental Chemical Exposures among Women and their Association with Spontaneous Preterm Birth: NHANES 2015-2016 and CHAMACOS Cohorts

Abstract

Background: Exposures to adverse environmental chemicals have been related to numerous adverse health outcomes including preterm birth (PTB). Populations who are disproportionately exposed to these adverse chemical exposures have not been fully described. Further, chemical risk factors for spontaneous preterm birth (sPTB), the most common subtype, remain insufficiently characterized. Methods: We used data from the 2015-2016 National Health and Nutrition Examination Survey (NHANES) and survey-weighted linear regression models to examine the distribution of bisphenol A (BPA), diphenyl phosphate (DPP), and mono(2-ethylhexyl) phthalate (MEHP) in women ages 18-43 by race/ethnicity, poverty status, and education. We also used data from the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) study of pregnant women to examine associations of BPA, DPP, and di(2-ethylhexyl) phthalate (DEHP) urinary concentrations measured during pregnancy with gestational age at birth and odds of sPTB. Adjusted linear regression models and logistic regression models were fit to compute beta estimates and odds ratios, along with corresponding 95% confidence intervals (95% CIs). Results: In our NHANES sample, lower urinary DPP concentration was found among Hispanic individuals who did not identify as Mexican-American (0.75, 95% CI: 0.56, 1.01, p=0.03) and among individuals who identified as another race/ethnicity or multiracial (0.72, 95% CI: 0.55, 0.95, p=0.01) compared to White individuals. We also identified marginally higher urinary MEHP concentrations among Mexican-American individuals compared to White individuals and marginally lower DPP concentrations among those who did not receive a high school diploma compared to those who did, although these results were not statistically significant. In the CHAMACOS cohort, maternal urinary BPA concentration (ng/mL) was associated with significantly higher odds of sPTB (OR=8.3, 95% CI: 1.8, 37.6, p=0.006). Although maternal urinary BPA concentration was inversely related to gestational age (-4.2 days, 95% CI: -8.8, 0.4, p=0.07), the association did not reach statistical significance. Maternal urinary DEHP concentration (µmol/mL) was marginally associated with higher odds of sPTB (OR=3.1, 95% CI: 0.8, 11.4, p=0.09) but was not associated with gestational age. Maternal urinary DPP was not associated with odds of sPTB or gestational age. Conclusion: Urinary DPP concentration was lower among non-Mexican-American Hispanic individuals and those who identified as another race/ethnicity or multiracial compared to non-Hispanic White individuals. Maternal urinary BPA concentration was positively associated with odds of sPTB in the CHAMACOS cohort. Further investigations of distribution of DPP and other chemical exposures among women are important to identify populations at risk. Future studies in diverse cohorts are also needed to examine associations of BPA exposure during critical windows of exposure with risk of sPTB.