Prenatal Exposure to Air Pollutants Associated with Allergic Diseases in Children: Which Pollutant, When Exposure, and What Disease? A Systematic Review and Meta-analysis

This systematic review aims to identify the association between prenatal exposure to air pollutants and allergic diseases in children, focusing on specific pollutants, timing of exposure, and associated diseases. We searched PubMed, Scopus, and Web of Science for English articles until May 1, 2023, examining maternal exposure to outdoor air pollutants (PM₁, PM_2.5, PM₁₀, NO, NO₂, SO₂, CO, and O₃) during pregnancy and child allergic diseases (atopic dermatitis (AD), food allergy (FA), asthma (AT) and allergic rhinitis (AR)/hay fever (HF)). The final 38 eligible studies were included in the meta-analysis. Exposure to PM_2.5 and NO₂ during pregnancy was associated with the risk of childhood AD, with pooled ORs of 1.34 (95% confidence interval (CI), 1.10–1.63) and 1.10 (95%CI, 1.05–1.15) per 10 µg/m³ increase, respectively. Maternal exposure to PM₁, PM_2.5, and NO₂ with a 10 µg/m³ increase posed a risk for AT, with pooled ORs of 1.34 (95%CI, 1.17–1.54), 1.11 (95%CI, 1.05–1.18), and 1.07 (95%CI, 1.02–1.12), respectively. An increased risk of HF was observed for PM_2.5 and NO₂ with a 10 µg/m³ increase, with ORs of 1.36 (95%CI, 1.17–1.58) and 1.26 (95%CI, 1.08–1.48), respectively. Traffic-related air pollutants (TRAP), particularly PM_2.5 and NO₂, throughout pregnancy, pose a pervasive risk for childhood allergies. Different pollutants may induce diverse allergic diseases in children across varying perinatal periods. AT is more likely to be induced by outdoor air pollutants as a health outcome. More research is needed to explore links between air pollution and airway-derived food allergies.