Drawing from data involving roughly 25 million people globally, an international research team has shown that prolonged exposure to ambient PM2.5 significantly raises the risk of asthma in both children and adults. The team found that nearly 30 percent of new asthma cases worldwide are associated with fine particulate matter (PM2.5), underscoring the serious threat that air pollution poses to public health.
Currently, asthma remains an untreatable condition that greatly diminishes quality of life, characterized by recurring symptoms such as wheezing, coughing, and difficulty breathing. About 4 percent of the global population is currently affected by asthma, with over 30 million new cases diagnosed each year. Evidence indicates that long-term exposure to air pollution from fine particulate matter (PM2.5) is a significant risk factor for developing asthma. However, variations in results from previous epidemiological studies have left this health risk subject to debate, as while some studies indicate an increased risk, others find no clear link.
To clarify this issue, Dr. Ruijing Ni, the lead author of the study published in the journal One Earth, along with her team at the Max Planck Institute for Chemistry, conducted an extensive global meta-analysis in collaboration with researchers from China, the USA, and Australia. They analyzed data from 68 epidemiological studies carried out in 2019 across 22 countries, including regions in North America, Western Europe, East Asia, South Asia, and Africa. Their findings have led to a solid conclusion with a high degree of confidence that long-term exposure to ambient PM2.5 is linked to asthma.
11 percent of new asthma cases in Germany are due to particulate matter
“We estimate that in 2019, nearly a third of asthma cases globally can be traced back to long-term PM2.5 exposure, amounting to 63.5 million existing cases and 11.4 million new cases. In Germany, pollution could have contributed to 11 percent of new asthma cases, which translates to about 28,000 individuals. Additionally, we found that the link between PM2.5 and asthma is much stronger in children compared to adults, indicating that younger individuals are more vulnerable,” explains Dr. Ni.
Normally, the complete development of lung and immune systems is achieved by early adulthood. Therefore, children may be more at risk from air pollution, which can cause oxidative stress in the airways, inflammation, heightened sensitivity, and altered immune responses, contributing to allergy sensitivity, all of which are factors in asthma development.
Using this data, the team also created exposure-response curves for asthma in children and adults. These curves are valuable tools that help quantify health risks by showing how varying levels of exposure to substances like PM2.5 are related to the severity of health effects like asthma risk. The curves were developed by integrating evidence from various countries and regions with different income levels, capturing the global diversity in PM2.5 exposure. “This work is essential for quantifying the global health impacts of air pollution,” remarks Prof. Yuming Guo, an epidemiologist at Monash University.
Consideration of countries with various income levels and PM pollution
In low- and middle-income countries (LMICs), people often experience higher levels of air pollution and suffer more from PM2.5. Conversely, there has been less research on the health impacts of PM2.5 in these areas, as most studies have focused on North America and Western Europe. For this reason, conducting a global health impact assessment concerning PM2.5 exposure requires applying associations found in high-income countries to LMICs, which can create significant uncertainty due to differences in pollution sources, healthcare systems, and demographic characteristics.
By incorporating evidence from several LMICs, the researchers minimized this limitation and made the exposure-response curves applicable for assessing asthma burden from city to global levels, as well as capturing health benefits related to reductions in air pollution, such as the benefits resulting from policy-driven pollution control measures.
“Our results stress the immediate necessity for policymakers to implement strict regulations to continually fight against air pollution, while individual protective measures like wearing masks can also help lessen personal exposure and lower asthma risk,” emphasizes Prof. Yafang Cheng, the chief author of the study and director at the Max Planck Institute for Chemistry.
This study was carried out by researchers from the Max Planck Institute for Chemistry (Germany), the Institute of Atmospheric Physics at the Chinese Academy of Sciences (China), the University of Washington (USA), and Monash University (Australia).
