Influence of Outdoor Air Pollutants on Asthma: A Narrative Review

Abstract

Asthma is a chronic lung disease affecting individuals across all age groups, contributing to significant morbidity and mortality. Exposure to air pollutants is a major factor in both the development and exacerbation of asthma symptoms. This study reviewed the impact of key air pollutants, including nitrogen dioxide (NO₂), particulate matter with a diameter ≤2.5 μm (PM_2.5) or ≤10 μm (PM₁₀), and ozone (O₃), on asthma outcomes. Our analysis of 20 studies showed significant associations between exposure to these pollutants and increased asthma incidence and prevalence, particularly in children. Specifically, pollutants such as elemental carbon (EC), benzene, NO₂, PM₁₀, and sulfur dioxide (SO₂) were found to be significantly associated with asthma development in children, while NO₂ and PM_2.5 were linked to asthma exacerbations in both children and adults. Additionally, hospitalizations and emergency room visits were positively correlated with exposure to PM_2.5 and O₃ in both children and adults, and the elderly showed significant associations with O₃ exposure. Although asthma-related mortality was not directly linked to specific pollutants, a few studies indicated a broader association between exposure to pollutants like NO₂ and PM_2.5 and increased overall mortality. These findings highlight the importance of reducing exposure to outdoor air pollutants to mitigate asthma risk and improve public health outcomes, particularly in vulnerable populations like children and the elderly.