Association of phthalate exposure with pulmonary function in adults: NHANES 2007-2012.

Background: Epidemiological evidence for the adverse effect of phthalate exposure on respiratory health is on the rise, but cross-sectional studies regarding its effects on lung function are limited and contradictory, especially in adults.

Objective: To assess the associations between individual and a mixture of urinary phthalate metabolites and adult pulmonary function in the United States, and to identify which ones were primarily responsible for impaired respiratory function.

Methods: We obtained a cross-sectional data on 3788 adults aged 20 years and older from the National Health and Nutrition Examination Survey (2007-2012). Respiratory function was evaluated using spirometry, and phthalate exposure was assessed by measuring the levels of ten urinary phthalate metabolites. The effects of individual and mixed phthalate metabolites exposure on lung function were assessed using multivariate linear regression models and the repeated holdout weighted quantile sum (WQS) regression models, respectively, after adjusting for potential confounders including age, gender, family poverty income ratio, body mass index, and serum cotinine.

Results: When modeled as continuous variables or quantiles, urinary phthalate metabolites, including mono-ethyl phthalate (MEP), mono-n-butyl phthalate, mono-iso-butyl phthalate, mono-benzyl phthalate, mono-(2-ethyl-5-oxohexyl) phthalate, mono-(2-ethyl-5-hydroxyhexyl) phthalate, mono-(2-ethyl-5-carboxypentyl) phthalate (MECPP), mono-(3-carboxypropyl) phthalate, and mono-carboxyoctyl phthalate, were identified to be negatively associated with forced vital capacity in percent predicted values (ppFVC) and forced expiratory volume in the first second in percent predicted values (ppFEV1). In addition, per each decile increase in the WQS index, ppFVC (β = -2.87, 95% CI: -3.56, -2.08) and ppFEV1 (β = -2.53, 95% CI: -3.47, -1.54) declined significantly, primarily due to the contribution of MEP and MECPP. Furthermore, there were no significant interactions between co-exposure to urinary phthalate metabolites and each covariate.

Conclusion: Our findings reveal that urinary phthalate metabolites are significantly associated with adult respiratory decrements, with diethyl and di-(2-ethylhexyl) phthalate contributing the most to the impaired lung function.