Phthalates mixture on allergies and oxidative stress biomarkers among children: The Hokkaido study

BACKGROUND: Exposure to individual phthalates and the mediation effect of oxidative stress in association with asthma and allergic symptoms have been studied previously. Little is known about the mixture effect of phthalates on health outcomes. Thus, we investigated the effect of a mixture of ten phthalate metabolites in association with wheeze, rhino-conjunctivitis, and eczema. The mediating effect of three oxidative stress biomarkers was also assessed. METHODS: Levels of 10 phthalate metabolites and 3 oxidative stress biomarkers were measured in 386 urine samples from 7-year-old children. Parents reported demographic and allergic symptoms using ISAAC questionnaires. Logistic regression for individual metabolites and mixture analysis weighted quantile sum (WQS) and Bayesian kernel machine regression (BKMR) were fitted to examine the association between phthalate metabolite exposure and health outcomes. Baron and Kenny's regression approach was used for mediation analysis. RESULTS: In logistic regression model showed mono (2-ethyl-5-carboxypentyl) phthalate (MECPP) (OR = 1.41, 95% CI 1.02-1.97) and mono carboxy-isononyl phthalate (cx-MINP) (OR = 1.40, 95% CI 1.07-1.86) were associated with wheeze. The WQS index had a significant association (OR = 1.46, 95% CI 1.09-1.96) with wheeze and (OR = 1.40, 95% CI 1.07-1.82) with eczema. Mono-isononyl phthalate (MINP) and mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP) were the most highly weighted metabolites. In the BKMR model, diisononyl phthalate (DINP) metabolites showed the highest group posterior inclusion probability (PIP). Among DINP metabolites, MINP in wheeze, cx-MINP in rhino-conjunctivitis and OH-MINP in eczema showed the highest conditional PIPs. The overall metabolites mixture effect was associated with eczema. We did not find any mediation of oxidative stress in the association between phthalates and symptoms. No significant association between phthalate metabolites and oxidative stress was observed in this study. CONCLUSION: Mixture of phthalate metabolites were associated with wheeze and eczema. The main contributors to the association were DEHP and DINP metabolites. No mediation of oxidative stress was observed.