Associations of urinary phthalates with body mass index, waist circumference and serum lipids among females: National Health and Nutrition Examination Survey 1999-2004

Background/Objectives: Exposure to environmental chemicals could be one of the contributors to the increasing obesity epidemic. Very little is known about the association of phthalates, ubiquitous chemicals widely used in consumer products, with obesity and lipid metabolism. This study investigated the association of urinary phthalate metabolites and, for the first time, the ratios of the major metabolites of the most common phthalate, di-2-ethylhexyl phthalate, with body mass index (BMI), waist circumference and serum lipid levels in the US female population. Methods: This cross-sectional study used the data from the National Health and Nutrition Examination Survey, 1999-2004 and was restricted to women aged ≥ 18 years, who were not pregnant and had no history of diabetes. Using multivariate ordered logistic regression, we examined associations of seven urinary phthalate metabolites and their metabolic ratios with the BMI, waist circumferences, total cholesterol, triglycerides and high- and low-density lipoprotein cholesterol. Results: BMI was positively associated with monobutyl phthalate (MBP) and mono-2-ethylhexyl phthalate (MEHP) (odds ratio (OR)=1.13; 95% confidence interval (CI), 1.03-1.23 and OR=1.12; 95% CI, 1.03-1.23, respectively). Waist circumference was positively associated with MBP (OR=1.13; 95% CI, 1.03-1.24). A higher ratio of MEHP to mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) was positively associated with both BMI (OR=1.21; 95% CI, 1.09-1.34) and waist circumference (OR=1.20; 95% CI, 1.10-1.31). There were no other significant associations. Conclusions: A higher metabolic ratio of MEHP to MEHHP, reflective of slower oxidative conversion of MEHP, is associated with greater BMI and waist circumference.