Association between air pollution and allergic upper respiratory diseases: a meta-analysis

The prevalence of allergic upper respiratory diseases is rising, and while air pollution may worsen them, study results vary, and comprehensive analyses are lacking. This study aimed to systematically evaluate the link between air pollution and these diseases (allergic rhinitis, asthma and chronic sinusitis (with/without nasal polyps)) to provide evidence for reducing their prevalence. A systematic search of PubMed, Embase, Web of Science and Scopus was conducted to find studies published up to 1 September 2024, regarding association between air pollution and allergic upper respiratory diseases. Meta-analyses calculated odds ratios and 95% confidence intervals for the outcomes. Sensitivity and subgroup analyses were performed to explore heterogeneity, and publication bias was assessed using Egger and Begg tests with funnel plots. We included 64 studies with 12 440 647 participants. The prevalence of allergic rhinitis, asthma and chronic sinusitis due to air pollution was 16%, 11% and 12%, respectively. Allergic rhinitis was linked to nitrogen dioxide (NO₂) (OR 1.083), particulate matter with aerodynamic diameter <10 µm (PM₁₀) (OR 1.026) and <2.5 µm (PM_2.5) (OR 1.104), sulfur dioxide (SO₂) (OR 1.116), ozone (OR 1.058) and carbon monoxide (CO) (OR 1.070). Asthma was associated with NO₂ (OR 1.146), PM_2.5 (OR 1.087), PM₁₀ (OR 1.037), polluted air (OR 1.038), ozone (OR 1.032), SO₂ (OR 1.090) and CO (OR 1.184). Chronic sinusitis was linked to PM_2.5 (OR 1.135), polluted air (OR 1.767), NO₂ (OR 1.091), SO₂ (OR 1.08), CO (OR 1.13), PM₁₀ (OR 1.22) and oxides of nitrogen (OR 1.18). Subgroup analyses showed that age (especially the young), region (especially in Europe), gender (especially men) and pollutant concentration (particularly high levels of pollution) affected these associations. Air pollution is positively correlated with prevalence of allergic rhinitis and asthma, increasing risk of allergic upper respiratory tract diseases.