Background: Phthalates are used in PVC plastics, food packaging, and personal care products. Use of phthalates in certain children's products has been regulated in some countries due to possible toxicity, but whether this has resulted in reduced exposure among children is unknown. Aims: To describe temporal patterns and predictors of early childhood phthaiate exposure. Methods: Urine samples, socioeconomic status (SES) and children's dietary information were longitudinally collected from children in the Health Outcomes and Measures of the Environment Study from ages 1 to 5. Phthalates were grouped into di-2-ethylhexyl (DEHP), high molecular weight (HMW), and low molecular weight (LMW) metabolites. We used linear mixed models to estimate phthaiate metabolite differences over time and according to sociodemographic and dietary factors. Results: We collected 1,100 urine samples from 325 children. After adjustment for SES, age, and sex, black children had LMW phthaiate concentrations 60% higher (95% Confidence Interval [CI]:33, 93) than whites, but similar HMW and DEHP metabolite concentrations. Diet was not associated with phthaiate metabolites. LMW metabolites decreased by 37% between 2003 and 2006 after adjustment for age (CI:-55, -13) and by 43% per year in age after adjustment for year of birth (CI:-46, -41). Age associated changes in DEHP and HMW metabolites depended on year of birth, where children born later had larger declines in metabolite concentrations. DEHP and HWM metabolite concentrations declined 16% and 23% per year among children born in 2003, respectively vs. 31% for both metabolites among children born in 2006. A 3-year old born in 2006 had DEHP and HMW metabolite concentrations 7% and 14% lower than a 3-year old born in 2003, respectively. Conclusions: Exposure to phthalates decreased over the course of the study as a result of both increasing age and trends in exposure over time, suggesting that regulations implemented in 2008 may have resulted in reduced phthaiate exposure among children in the US.
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