Context: Experimental studies have demonstrated that phthalate exposure is associated with skeletal malformations and an imbalance in bone homeostasis. However, few studies have evaluated the association between phthalates and human bone health.
Objectives: We evaluated whether urinary phthalate metabolites were associated with total hip and femur neck bone mineral density (BMD) and osteoporosis in postmenopausal women (≥50 y old).
Design: We analyzed data from the 2005-2008 National Health and Nutrition Examination Survey (NHANES) for 398 postmenopausal women ≥ 50 years of age. Eleven phthalate metabolites were selected with a detection rate ≥ 60% and were categorized into quartiles. Total hip and femur neck BMD measurements were obtained using dual-energy x-ray absorptiometry bone densitometry. Osteoporosis was defined based on the World Health Organization criteria, with thresholds of 0.64 and 0.56 g/cm(2) or less for the total hip and femur neck, respectively.
Results: Increases in the urinary mono-n-butyl phthalate, mono-(3-carboxypropyl) phthalate, and monobenzyl phthalate quartiles were significantly associated with reduced total hip or femur neck BMD. Postmenopausal women with the highest levels of mono-(3-carboxypropyl) phthalate, mono(carboxyoctyl) phthalate, and the sum of the three di(2-ethylhexyl) phthalate metabolites were more likely to have an increased risk for total hip or femur neck osteoporosis than those with the lowest levels of these metabolites.
Conclusion: Urinary phthalate metabolites were associated with low BMD and high osteoporosis risk in postmenopausal women. Our findings suggest that background phthalate exposure may unfavorably affect bone homeostasis and BMD in humans.