Asthma in inner-city children at 5-11 years of age and prenatal exposure to phthalates: the Columbia Center for Children's Environmental Health Cohort

Abstract

Background: Studies suggest that phthalate exposures may adversely affect child respiratory health.

Objectives: We evaluated associations between asthma diagnosed in children between 5 and 11 years of age and prenatal exposures to butylbenzyl phthalate (BBzP), di-n-butyl phthalate (DnBP), di(2-ethylhexyl) phthalate (DEHP), and diethyl phthalate (DEP).

Methods: Phthalate metabolites were measured in spot urine collected from 300 pregnant inner-city women. Children were examined by an allergist or pulmonologist based on the first parental report of wheeze, other respiratory symptoms, and/or use of asthma rescue/controller medication in the preceding 12 months on repeat follow-up questionnaires. Standardized diagnostic criteria were used to classify these children as either having or not having current asthma at the time of the physician examination. Children without any report of wheeze or the other asthma-like symptoms were classified as nonasthmatics at the time of the last negative questionnaire. Modified Poisson regression analyses were used to estimate relative risks (RR) controlling for specific gravity and potential confounders.

Results: Of 300 children, 154 (51%) were examined by a physician because of reports of wheeze, other asthma-like symptoms, and/or medication use; 94 were diagnosed with current asthma and 60 without current asthma. The remaining 146 children were classified as nonasthmatic. Compared with levels in nonasthmatics, prenatal metabolites of BBzP and DnBP were associated with a history of asthma-like symptoms (p < 0.05) and with the diagnosis of current asthma: RR = 1.17 (95% CI: 1.01, 1.35) and RR = 1.25 (95% CI: 1.04, 1.51) per natural log-unit increase, respectively. Risk of current asthma was > 70% higher among children with maternal prenatal BBzP and DnBP metabolite concentrations in the third versus the first tertile.

Conclusion: Prenatal exposure to BBzP and DnBP may increase the risk of asthma among inner-city children. However, because this is the first such finding, results require replication.

Figure 1

Association between maternal prenatal (ln)phthalate metabolite concentrations and presence (n = 154) compared with the absence (n = 146) of a history of asthma-like symptoms on repeat questionnaires administered between child ages 5 and 11 years. RRs were estimated using Poisson regression with robust standard error estimation using the generalized estimating equations controlling for maternal asthma, household tobacco smoke exposure, maternal prenatal BPA, maternal prenatal demoralization, and maternal prenatal specific gravity. *p < 0.05.

Figure 2

Association between maternal prenatal (ln)phthalate metabolite concentrations and diagnosis of current asthma (n = 94) compared with nonasthmatic (n = 146) between child ages 5 and 11 years. RRs were estimated using Poisson regression with robust standard error estimation using the generalized estimating equations controlling for maternal asthma, household tobacco smoke exposure, maternal prenatal BPA, maternal prenatal demoralization, child age, and maternal prenatal specific gravity. *p < 0.05.

Figure 3

Association between maternal prenatal (ln)phthalate metabolites concentrations and diagnosis as not current asthma among children with a history of the asthma-like symptoms (n = 60) compared with children without any history of asthma-like symptoms classified as nonasthmatics (n = 146). RRs were estimated using Poisson regression with robust standard error estimation using the generalized estimating equations controlling for maternal asthma, household tobacco smoke exposure, maternal prenatal BPA, maternal prenatal demoralization, child age, and maternal prenatal specific gravity. *p < 0.05.