Ambient air pollutants increase the risk of immunoglobulin E-mediated allergic diseases: a systematic review and meta-analysis

Immunoglobulin E (IgE)-mediated allergic diseases, including eczema, atopic dermatitis (AD), and allergic rhinitis (AR), have increased prevalence in recent decades. Recent studies have proved that environmental pollution might have correlations with IgE-mediated allergic diseases, but existing research findings were controversial. Thus, we performed a comprehensive meta-analysis from published observational studies to evaluate the risk of long-term and short-term exposure to air pollutants on eczema, AD, and AR in the population (per 10-μg/m³ increase in PM_2.5 and PM₁₀; per 1-ppb increase in SO₂, NO₂, CO, and O₃). PubMed, Embase, and Web of Science were searched to identify qualified literatures. The Cochran Q test was used to assess heterogeneity and quantified with the I² statistic. Pooled effects and the 95% confidence intervals (CIs) were used to evaluate outcome effects. A total of 55 articles were included in the study. The results showed that long-term and short-term exposure to PM₁₀ increased the risk of eczema (PM₁₀, RR_long = 1.583, 95% CI: 1.328, 1.888; RR_short = 1.006, 95% CI: 1.003-1.008) and short-term exposure to NO₂ (RR_short = 1.009, 95% CI: 1.008-1.011) was associated with eczema. Short-term exposure to SO₂ (RR_short: 1.008, 95% CI: 1.001-1.015) was associated with the risk of AD. For AR, PM_2.5 (RR_long = 1.058, 95% CI: 1.014-1.222) was harmful in the long term, and short-term exposure to PM₁₀ (RR_short: 1.028, 95% CI: 1.008-1.049) and NO₂ (RR_short: 1.018, 95% CI: 1.007-1.029) were risk factors. The findings indicated that exposure to air pollutants might increase the risk of IgE-mediated allergic diseases. Further studies are warranted to illustrate the potential mechanism for air pollutants and allergic diseases.