Asthma is a chronic and incurable respiratory disease that affects approximately 4 percent of the global population, with more than 30 million new cases emerging annually. Long-term exposure to fine particulate matter (PM2.5) in air pollution has been identified as a significant risk factor for developing asthma. However, previous epidemiological studies have yielded inconsistent results, with some showing an increased risk while others found no association between PM2.5 exposure and asthma development.
To address these discrepancies, Dr. Ruijing Ni and her colleagues at the Max Planck Institute for Chemistry conducted a comprehensive global meta-analysis involving data from 68 epidemiological studies spanning 22 countries. Their findings, published in the journal One Earth, provide strong evidence supporting an association between long-term exposure to ambient PM2.5 and asthma, with a high level of confidence. The study estimates that nearly one-third of asthma cases worldwide in 2019 were attributable to PM2.5 exposure, resulting in 63.5 million existing cases and 11.4 million new cases.
The research team also observed that children are more vulnerable to the effects of air pollution on asthma compared to adults, likely due to the ongoing maturation of lung and immune function in early adulthood. Children exposed to air pollution may experience oxidative stress, inflammation, hyper-responsiveness in airways, changes in immune responses, and heightened sensitization to allergens, all of which contribute to asthma development. Exposure-response curves were established for both childhood and adult asthma to quantify the relationship between PM2.5 exposure levels and asthma risk.
Populations in low- and middle-income countries (LMICs) are often exposed to higher levels of air pollution and bear a greater burden of PM2.5-related health effects. Previous research on the health impacts of PM2.5 has primarily focused on high-income countries, leading to challenges in extrapolating exposure-response associations to LMICs. By including data from various income levels and regions, the researchers were able to create exposure-response curves that account for global variations in PM2.5 exposure and assess the burden of asthma attributable to air pollution on a city to global scale.
The study underscores the urgent need for policymakers to implement stringent regulations to combat air pollution and reduce asthma risks. Personal protective measures, such as wearing masks, can also help individuals reduce their exposure to air pollution and mitigate the risk of developing asthma. The research was conducted by a collaborative team from Max Planck Institute for Chemistry (Germany), Institute of Atmospheric Physics at the Chinese Academy of Sciences (China), University of Washington (USA), and Monash University (Australia), highlighting the global effort to address the impact of air pollution on respiratory health.