A recent study published in One Earth has reviewed existing evidence on how long-term exposure to fine particulate matter (PM2.5) affects the risk of developing asthma.
Global Burden of Asthma
Asthma affects over 250 million people worldwide. Symptoms such as wheezing and coughing can severely impact daily life and, in severe cases, can be life-threatening. Managing asthma requires continuous medication and healthcare, leading to financial burdens for individuals and society.
PM2.5, which consists of particles 2.5 microns or smaller, is a potential risk factor for asthma. However, previous studies on this connection have produced mixed results. Most research has focused on high-income countries, limiting its relevance to other regions.
More research is essential to understand the relationship between asthma and PM2.5 since air pollution is a modifiable risk factor. Clear evidence could guide policies and personal actions to reduce exposure.
Study Findings
The current study systematically reviewed long-term PM2.5 exposure and asthma risk, analyzing 1,027 records from studies involving over 25 million participants across 22 countries. The researchers conducted meta-analyses to assess PM2.5’s impact on asthma risk, comparing asthma-related health burdens to those from other diseases associated with PM2.5, like lung cancer.
Initially, the review identified 3,406 studies. Among them, 41 focused on childhood asthma and 18 on adult asthma. The studies covered a wide range of PM2.5 exposure, affecting more than 90% of the global population.
The analysis found that a 10 µg/m³ increase in PM2.5 concentrations was linked to a 21.4% rise in childhood asthma and a 7.1% increase in adult asthma. Exposure to PM2.5 during early life significantly raised asthma risk, which continued to grow with age. However, the researchers noted high variation across studies due to different exposure assessment methods and PM2.5 compositions.
Policy Implications
The prevalence of asthma has risen sharply since the 21st century, especially in low- and middle-income countries. Currently, about 4% of the global population has asthma, with 30 million new cases diagnosed each year.
The study found a linear relationship between PM2.5 levels and asthma risk. In 2019, roughly one in three asthma cases worldwide were linked to PM2.5 exposure. Children are particularly vulnerable to developing asthma from PM2.5, likely due to age-related factors. There is limited evidence regarding PM2.5’s impact on asthma mortality, as most studies have focused on prevalence and incidence.
Different components of PM2.5 affect asthma risk in various ways. For instance, organic matter and black carbon have more significant impacts than inorganic particles. While other pollutants often correlate with PM2.5, adjusting for these does not greatly alter the connection between PM2.5 and asthma.
Overall, the findings stress the need to reduce air pollution, especially PM2.5, to lower asthma risks for both adults and children. Stronger air quality legislation could alleviate asthma burdens and enhance public health.
Strengths and Limitations
The study has some limitations, including the varying methods used to measure PM2.5, which could lead to biased risk estimates. Future studies using high-resolution data could improve measurement accuracy. The diversity among studies highlights the need for standardized methods to assess PM2.5 exposure and diagnose asthma.
However, the study’s strengths include a large and diverse sample size, along with strict data criteria aimed at minimizing bias and enhancing result reliability. Still, there is a notable lack of high-quality longitudinal studies conducted in low- and middle-income countries.
Conclusion
This comprehensive global meta-analysis, involving over 25 million individuals from diverse backgrounds, found that long-term exposure to PM2.5 significantly increases asthma risk in both adults and children.
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