Seasonal viruses modify short-term air pollution effects on pediatric wheeze and asthma: a time-series study

Abstract Background Short-term exposure to air pollution is a known trigger for pediatric wheeze-associated disorders (WAD), such as acute asthma and virus-induced wheezing, yet few air pollution studies account for concurrent viral circulation, which may confound or modify the observed associations. This study aims to assess whether viral circulation confounds or modifies the association between daily levels of air pollution and pediatric WAD emergency department (ED) visits. Methods We conducted a time-series analysis of 12,603 WAD ED visits among children 2–18 years old across eight hospitals in the Netherlands (2016–2023). Quasi-Poisson models estimated associations between same-day nitrogen dioxide (NO₂), fine and coarse particulate matter (PM₂․₅, PM₁₀) and ozone (O₃) and daily WAD ED visits, and adjusted for seasonality, meteorology and pollen. Base models were compared with confounding and interaction models, which included weekly rhinovirus (RV) or respiratory syncytial virus (RSV) positivity ratios as covariates or interaction terms. Results In the base models, 3-day lag exposure to NO₂ and PM2.5 was associated with an increase in WAD ED visits (NO2: ER% 2.9, 95% CI 0.4—5.6; p = 0.025. PM2.5: ER% 3.6, 95% CI 0.4 – 6.9; p = 0.026). Associations were similar after adjustment for viral activity. The interaction models revealed attenuated effect estimates for NO2, PM2.5 and PM10 during relatively high RV activity. O₃ showed a negative association during low RV periods. Conclusions In this study, circulating RV modifies, rather than confounds, the association between short-term air pollution and pediatric WAD ED visits. Considering viral activity improves the interpretation of pollution–health associations and may explain inconsistencies across studies.