The association of co-exposure to
polycyclic aromatic hydrocarbons (PAHs) and phthalates (
PAEs) with blood cell-based inflammatory
biomarkers is largely unknown. We conducted a panel study of 144 children aged 4-12 years, with up to 3 repeated visits across 3 seasons. For each visit, we collected the first-morning urine for 4 consecutive days and fasting blood on the day of physical examination. We developed a gas chromatography/tandem mass spectrometry method to detect the metabolites of 10 PAHs (
OH-PAHs) and 10
PAEs (mPAEs) in urine samples. We employed linear mixed-effects models to evaluate the individual associations of each
OH-PAH and mPAE with blood cell-based inflammatory
biomarkers over different lag times. Bayesian kernel machine regression (BKMR) and quantile g-computation were used to evaluate the overall associations of
OH-PAHs and mPAEs mixtures with blood cell-based inflammatory
biomarkers. After multiple adjustments, we found positive associations of summed hydroxylphenanthrene (∑OHPHE), summed
OH-PAHs, and
mono-n-butyl phthalate with inflammatory
biomarkers such as neutrophil count, neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, and the systemic immune-
inflammation index (SII) at lag 0 (the day of physical examination). Each 1% increase in ∑OHPHE was related to a 0.18% (95% confidence interval: 0.10%, 0.25%) increase in SII, which was the strongest among the above associations. The results of BKMR and quantile g-computation suggested that co-exposure to PAHs and
PAEs mixture was associated with an elevated white blood cell count, neutrophil count, neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, and SII, to which ∑OHPHE and
1-hydroxypyrene (1-OHPYR) might be the major contributors. In addition, gender and age modified the associations of ∑OHPHE and 1-OHPYR with inflammatory
biomarkers, where girls and younger children were more susceptible. In conclusion, co-exposure to PAHs and
PAEs was associated with elevated
inflammation in children, in which ∑OHPHE and 1-OHPYR might play important roles.