Low and high molecular weight metabolite concentrations in relationship to adiposity in a multi-site, multi-racial cohort of children

Abstract

BACKGROUND AND AIM: Low molecular weight (LMW) and high molecular weight (HMW) phthalates are used in multiple everyday products, many of which are bioavailable to children. Evidence concerning the effects of these phthalates on child adiposity remain inconsistent. METHODS: Analyses included 540 racial/ethnically diverse children ages 4-8 in the Environmental Influences on Child Health Outcomes (ECHO) study, a follow-up of the NICHD Fetal Growth Studies. Urinary oxidative metabolites of three LMW and eleven HMW phthalates were determined using liquid chromatography tandem-mass spectrometry. Values were divided by molecular weight and summed to obtain composite LMW and HMW group values (nmol/ml) and natural log transformed. Outcomes were child’s body mass index (BMI) z-score, waist circumference z-score, and percent body fat. Linear regression models were adjusted for urine specific gravity, gender, age, race/ethnicity, birth weight, prolonged exclusive breastfeeding, physical activity, fast-food consumption, smoke exposure, neighborhood traffic, mother’s education and pre-pregnancy BMI. RESULTS:All children had LMW and HMW phthalate group levels at or above the limit of detection. LMW levels were not associated with BMI z-score (β [95% CI]: 0.010 [-0.037. 0.057]), waist circumference z-score (β [95% CI]: -0.002 [-0.046, 0.042]) or percent body fat (β [95% CI]: -0.009 [-0.025, -0.007]). There was evidence of a possible interaction with race (p=0.09), with increased LMW levels in Black children being positively associated with percent body fat (β [95% CI]: 0.005 [0.001, 0.010]). HMW levels were not associated with BMI z-score (β [95% CI]: -0.003 [-0.084, 0.078]), waist circumference z-score (β [95% CI]: 0.021 [-0.055, 0.097]) or percent body fat (β [95% CI]: 0.0003 [-0.008, 0.008]). CONCLUSIONS:In this largely null cross-sectional analysis only LMW phthalates in Black children were associated with percent body fat. Additional research is needed to identify possible interactions between LMW phthalates, HMW phthalates and joint exposure to related chemicals. KEYWORDS: Phthalates, Obesity and metabolic disorders, Children's environmental health