Associations between Urinary Organophosphorous Flame Retardant Metabolites and Measures of Adiposity in the U.S. General Population: NHANES 2013-2014

Organophosphorous flame retardants (OPFRs) are synthetic chemicals commonly added to many consumer products, including furniture, electronics, and building materials. Emerging in vitro and in vivo animal studies suggest that OPFRs may alter metabolism and affect obesity risk via effects on sex and thyroid hormones, peroxisome-proliferator-activated receptors, and oxidative stress. In this study, we examined cross-sectional associations between five urinary OPFR metabolites [diphenyl phosphate(DPhP), Bis(1,3-dichloro-2-propyl) phosphate(BDCPP), Bis(2-chloroethyl) phosphate(BCEtP), Dibutyl phosphate(DBuP), and Bis(1-chloro-2-propyl) phosphate(BCPP)] with adiposity measures [obesity, body mass index(BMI) and waist circumference(WC)] among 1351 adults aged 20-80 years and 638 children aged 6-19 years participating in the US National Health and Nutrition Examination Survey. We estimated associations in multivariable logistic and linear regression models, adjusted for age, gender, race/ethnicity, urinary creatinine, smoking, diet, physical activity, and screen time. For adults, we observed increased prevalence odds of being obese vs. normal weight among those with detectable BCPP levels (adjusted Prevalence Odds Ratio (aPOR):1.78,95% Confidence Interval, CI:1.20,2.64) as well as increased prevalence odds of having a high vs. normal WC (aPOR:1.65,CI:1.17,2.32). Among children, we observed a significant inverse association between log10-DBuP concentrations and the prevalence odds of being obese vs. normal weight (aPOR:0.41, CI:0.22,0.77). Similar trends were observed with BMI z-scores (β:-0.36,p=0.02) and WC (β:-3.14,p=0.03). Overall, OPFR associations did not differ by gender among adults or children. Findings suggest that exposure to certain OPFRs may be differentially associated with body size among adults and children. Future prospective studies are needed to confirm these findings and take into account potential windows of susceptibility, including the prenatal period.