Temporal Trends in Exposure to Phthalates: Findings from the National Health and Nutrition Examination Survey 2001-2010

Abstract

Background: Phthalates are ubiquitous environmental contaminants and some may adversely affect human health. Butylbenzyl phthalate (BBzP), di-n-butyl phthalate (DnBP), and di(2-ethylhexyl) phthalate (DEHP) are being phased out and replaced by substitutes including di-iso-nonyl phthalate (DiNP), and di-iso-decyl phthalate (DiDP), however little is known about consequent trends in population-level exposures. Aims: To examine temporal trends in urinary concentrations of phthalate metabolites in the US general population, and whether trends vary by age, sex, race/ethnicity, or income. Methods: We combined data on 11 phthalate metabolites for 8626 participants from 2001-2002, 2003-2004, 2005-2006, 2007-2008, and 2009-2010 cycles of the National Health and Nutrition Examination Survey. We compared least square geometric mean (LSGM) concentrations of phthalate metabolites by cycle after creatinine adjustment. Results: LSGM concentrations of metabolites of diethyl phthalate (DEP), DnBP, BBzP, and DEHP decreased between 2001-2002 and 2009-2010 (Ptrend < 0.05). The percent decrease in LSGM concentrations ranged from 20% for the DnBP metabolite to 50% for the DEP metabolite and the molar sum of DEHP metabolites (?DEHP metabolites). In contrast, LSGM concentrations of metabolites of di-iso-butyl phthalate (DiBP), DiNP, and DiDP increased 220%, 160%, and 20%, respectively, over the study period (Ptrend < 0.05). Trends varied by age, sex, race/ethnicity, and income (Pinteraction < 0.05). For example, DEHP, DiNP, and DiDP metabolites were higher in children than adults but the gap between the groups narrowed over time. Conclusions: US population exposure to phthalates has changed in the last decade. These trends likely reflect shifts in commercial formulations, public awareness, and regulations.