Long-term exposure to PM_2.5 has significant adverse effects on childhood and adult asthma: A global meta-analysis and health impact assessment

Asthma affects more than 250 million people worldwide, making it a globally significant health threat. As one of the most important potential risk factors, the effects of long-term exposure to ambient fine particulate matter (PM_2.5) on asthma, especially in adults, remains unclear. Here, we comprehensively addressed this issue by integrating a systematic review, meta-analysis, exposure-response analysis, and health impact assessment based on evidence that emerged until May 2023. We show that, for every 10 μg/m³ increment in PM_2.5, the risk of childhood and adult asthma (i.e., prevalence, incidence, and mortality of all asthma types) increases by 21.4% (95% confidence interval [CI]: 11.4%–32.3%) and 7.1% (95% CI: 1.6%–12.9%), respectively. We estimate that, in 2019, nearly one-third of the global asthma cases are associated with PM_2.5 exposure. These findings emphasize that long-term PM_2.5 exposure significantly increases asthma risk in both children and adults. Continuous efforts regarding air pollution mitigation are therefore urgently needed.