Phthalate levels in indoor dust and associations to croup in the SELMA study

Phthalates are ubiquitous indoor pollutants which have been associated with child airway disease although results are inconclusive. This study examined associations between phthalate levels in residential indoor dust and croup during infancy. Settled indoor dust was collected in 482 homes of 6-month-old infants in the Swedish Environmental Longitudinal, Mother and child, Asthma and allergy (SELMA) study and analysed for seven phthalates and one phthalate replacement using gas chromatography tandem mass spectrometry. The incidence of parental reported croup at 12 months was 6.4% for girls and 13.4% for boys. Associations between phthalate dust levels and croup were analysed by logistic regression adjusted for potential confounders. We found significant associations between di-ethyl phthalate (DEP) and di-ethyl-hexyl phthalate (DEHP) in residential dust and parental reported croup (adjusted odds ratio (aOR) = 1.71; 95% CI: 1.08-2.73 and 2.07; 1.00-4.30, respectively). Stratified results for boys showed significant associations between DEP and butyl-benzyl phthalate (BBzP) in dust and infant croup (aOR = 1.86; 95% CI: 1.04-3.34 and 2.02; 1.04-3.90, respectively). Results for girls had questionable statistical power due to few cases. Our results suggest that exposure to phthalates in dust is a risk factor for airway inflammatory responses in infant children.