Background

Air pollution has been linked to respiratory diseases, while the effects of greenness remain inconclusive.ObjectiveWe investigated the associations between exposure to particulate matter (PM_2.5 and PM₁₀), black carbon (BC), nitrogen dioxide (NO₂), ozone (O₃), and greenness (normalized difference vegetation index, NDVI) with respiratory emergency room visits and hospitalizations across seven Northern European centers in the European Community Respiratory Health Survey (ECRHS) study.

Methods

We used modified mixed-effects Poisson regression to analyze associations of exposure in 1990, 2000 and mean exposure 1990–2000 with respiratory outcomes recorded duing ECRHS phases II and III. We assessed interactions of air pollution and greenness, and of atopic status (defined by nasal allergies and hay fever status) and greenness, on these outcomes.

Results

The analysis included 1675 participants, resulting in 119 emergency visits and 48 hospitalizations. Increased PM_2.5 by 5 μg/m³ was associated with higher relative risk (RR) of emergency visits (1990: RR 1.16, 95% CI: 1.00–1.35; 2000: RR 1.24, 95% CI: 0.98–1.57; 1990–2000: RR 1.17, 95% CI: 0.97–1.41) and hospitalizations (1990: RR 1.42, 95% CI: 1.00–2.01; 2000: RR 2.20, 95% CI: 1.43–3.38; 1990–2000: RR 1.44, 95% CI: 1.04–2.00). Similar trends were observed for PM₁₀, BC, and NO₂, with only PM₁₀ showing significant associations with hospitalizations across all periods. No associations were found for O₃. Greenness exposure was linked to more emergency visits in 2000 but to fewer hospitalizations in 1990. Significant interactions were observed between greenness and atopic status for emergency visits, and between NDVI with O₃ and BC for some time windows.

Conclusion

Long-term exposure to particulate matter was associated with increased emergency room visits and hospitalizations. Significant associations were observed for BC and NO₂ with hospitalizations. No link was found with O₃. Greenness indicated a lower risk of hospitalizations, but increased risks for emergency visits for those with atopic status.