Phthalates are a class of widely used synthetic chemicals found in commonly used materials and products. Epidemiological studies suggest
phthalate exposure is associated with
asthma outcomes, though most studies have not investigated phthalates as triggers of exacerbations in children diagnosed with
asthma. This study used data from the Home Air in Agriculture Pediatric Intervention Trial (HAPI) to examine relationships between
phthalate exposure and outcomes related to childhood
asthma exacerbation. We used measures of
phthalate metabolites and respiratory health measures including fractional exhaled
nitric oxide (FENO), the
Asthma Control Test (ACT), caregiver report of symptoms, and urinary
leukotriene E4 (uLTE4) to estimate longitudinal associations using mixed effects models, adjusted for covariates. For 100% (i.e., doubling) increases in mono-(2-ethyl-5-carboxypentyl)
phthalate (
MECPP), mono-2-ethylhexyl
phthalate (
MEHP), and mono-ethyl
phthalate (MEP), concentrations of FENO increased by 8.7% (95% CI: 0.7-17.3), 7.2% (95% CI: 0.0-14.9), and 6.4% (95% CI: 0.0-13.3), respectively. All
phthalate metabolites demonstrated associations with uLTE4, effect sizes ranging from an 8.7% increase in uLTE4 (95% CI: 4.3-12.5) for a 100% increase in
MEHP to an 18.1% increase in uLTE4 (95% CI: 13.3-23.1) for a 100% increase in MNBP. In models of caregiver report of symptoms, no
phthalate metabolites were significantly associated in primary models. No
phthalate metabolites were associated with standardized ACT score. Our results suggest urinary
phthalate metabolites are significant predictors of inflammatory
biomarkers related to
asthma exacerbation in children but not child and caregiver report of airway symptomatology.