INTRODUCTION
Previous studies reported that exposures to environmental pollutants are responsible for the increasing prevalence of allergic diseases.1,2 Here, we focused on phthalates, a group of chemicals commonly used as plasticizers that commonly have higher concentrations in children than adults.3 Phthalates can have adverse effects on the respiratory and immunological systems. Epidemiological studies reported positive associations between indicators of phthalate exposure and risk of asthma, and allergic diseases.4,5 Other studies reported that phthalates also adversely affect pulmonary functions.6,7Experimental studies demonstrated that exposure to phthalates increased the levels of T helper 2 (Th2) cells and cytokines, and also increased airway inflammation.8,9 Several clinical studies found an association between phthalate exposure and fractional exhaled nitric oxide (FeNO).5,8 The immunological mechanisms by which phthalate exposure leads to asthma and disruptions of lung function and airway inflammation are unknown. In addition, few studies have examined the association of phthalate exposure with allergic inflammation and lung function.
Recent studies identified periostin and chitinase-like proteins as biomarkers of asthma. Periostin promotes chronic allergic inflammation in response to Th2-associated cytokines by inducing proinflammatory cytokines.10 Chitinase-3-like protein 1, also known as YKL-40, is a glycoprotein secreted by various cell types, including macrophages, neutrophils, and airway epithelial cells.11 However, little is known about the levels or function of periostin and YKL-40 following exposure to environmental pollutants or other chemicals. We hypothesized that phthalate exposure may alter the serum levels of periostin and YKL-40.
Our primary objective was to determine the associations between phthalate exposure and pulmonary functions in a population-based sample of randomly selected sixth-grade students from 11 elementary schools in Korea. Our secondary objective was to examine the potential role of periostin and YKL-40 in mediating the relationship between phthalate exposure and airway dysfunction.