Prenatal phthalate exposures and childhood asthma among an inner-city birth cohort

Abstract

Background: Phthalates are widely used chemicals in consumer products. Prior studies suggest that exposures to certain phthalates may affect child respiratory health, but no studies have evaluated effects of prenatal exposure on child asthma. Methods: We measured metabolites of four phthalates in spot urine samples collected during pregnancy from n= 327 African American and Dominican women in New York City. The phthalates were butylbenzyl phthalate (BBzP), di-n-butyl phthalate (DnBP), di-2-ethylhexyl phthalate (DEHP) and diethyl phthalate (DEP). Children with a history of wheeze or other respiratory symptoms on repeat questionnaires were seen by a pediatric allergist or pulmonologist between ages 5-12 years. Current asthma was diagnosed using standardized criteria. Children with no history of wheeze or other asthma-related symptoms were considered non-asthmatic. Results: A total of 173 children had a history of asthma-related symptoms; n=104 were diagnosed as current asthma and n=69 as without current asthma (for overall current asthma rate of 104/327, 31.8%). Compared to non-asthmatic children, relative risk (RR) for current asthma increased per loge BBzP metabolites in maternal prenatal urine: RR=1.13 (95% CI 1.03, 1.24). The dose-response relationship was significant. Compared to children with prenatal BBzP metabolite concentrations in the 1st tertile, the relative risk for current asthma among children in the 2nd tertile was 1.48 (95% CI 0.97, 2.26) and in 3rd tertile was 1.78 (95% CI 1.09, 2.91) (p=0.02 for the trend test). No significant associations were seen between metabolites of the other three phthalates and current asthma. Compared to non-asthmatic children, logeDnBP metabolite concentrations were associated with children who had a history of wheeze and other asthma-related symptoms but were diagnosed as without current asthma (RR 1.32 [95% CI 1.03, 1.69) but no dose-response was apparent (p=0.68 for trend test). Conclusion: Prenatal exposure to BBzP may increase the risk of current asthma during childhood.