The Association of Prenatal and Infant Phthalate Exposure and Childhood Asthma Symptoms

INTRODUCTION: Childhood asthma is one of the leading chronic diseases among children. Environmental exposures may may increase the risk of asthma by altering organ system maturation trajectories during critical times of development. The purpose of this study was to examine the association between childhood asthma and respiratory symptoms and exposure to phthalates before and after birth.;METHODS: The Study for Future Families (SFF) cohort is a multi-state pregnancy cohort first recruited in 1999. Urine samples were collected from the pregnant woman and then her infant. This study initiated another follow-up phase where SFF children, now aged 5 to 11, were assessed for respiratory symptoms using a screening tool created specifically for this study based on previously validated tools. The screener was administered on two occasions (N=164 and N=113). Multivariable logistic regression was used to examine these associations while adjusting for child sex, child age, and prenatal maternal stress.;RESULTS: The study prevalence of doctor-diagnosed asthma (12% to 15%) was nearly equivalent to national estimates (13.3%). For exposure during the prenatal period, boys and girls showed increased risk for asthma with increasing concentrations of phthalate metabolites. Boys showed greater magnitudes of risk compared to girls. For example, the sum of di(2-ethylhexyl) phthalate metabolites (sumDEHP) was associated with odds ratios from 1.41 to 3.69 for boys and 1.03 to 1.59 for girls. However, for exposure during the postnatal period both boys and girls had lower risk of asthma with increased phthalate exposure. For instance, sumDEHP was associated with odds ratios from 0.17 to 0.41 in boys and 0.49 to 0.73 in girls. In both periods of time phthalate exposure showed interaction by sex. When assessing a wider developmental period, results mirrored the postnatal exposure data results. Boys and girls were protected with increasing phthalate exposures.;CONCLUSIONS: The association between phthalate exposure and childhood asthma seem to be sexually dimorphic. One explanation for this difference may be related to the endocrine disrupting properties of phthalates and the hormonal influences of these chemicals on the development and functioning of the lungs and immune system. Additional studies investigating this mechanism are warranted.