Abstract

Poor indoor air quality is linked to respiratory symptoms and disease, but interactions between indoor pollutants and microbial communities remain unclear. Evidence suggests microorganisms can interact with polycyclic aromatic hydrocarbons (PAHs) through degradation or attachment, potentially shaping indoor microbiomes. In the COPSACsevere cohort, we analyzed bed dust from 84 children (58 asthma, 26 controls). PAHs were measured by HPLC-FLD and microbiota profiled by 16S rRNA and ITS2 sequencing. Questionnaires captured sociodemographic and lifestyle factors. Associations were tested using PERMANOVA, Spearman correlations, and MaAsLin2. Bacterial community composition varied with the host factors age, sex, and parental education, but showed no association with PAH concentrations. Fungal diversity and composition were significantly associated with PAHs, especially pyrene and fluoranthene, which explained 6.1–6.3% variance (p < 0.05) and were positively correlated with Shannon diversity and evenness. Several fungal taxa including Lecanoraceae, Helotiales, and Circinaria correlated positively with PAHs. Asthma status was not associated with bacterial or fungal alpha and beta diversity metrics. PAHs selectively influenced fungal but not bacterial communities in bed dust. Although no asthma associations were detected and no mechanisms can be inferred, these findings highlight potential chemical–fungal interactions in indoor environments and their relevance for future respiratory health research. These results suggest that chemical exposures may shape specific components of indoor microbiomes independent of host disease status, emphasizing the need to integrate chemical–biological interactions in indoor exposure assessments in future environmental health studies and interventions.

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