Air pollution remains a critical global health concern, with fine particulate matter (PM2.5) posing significant risks to human health. The 2024 World Air Quality Report by IQAir provides a comprehensive analysis of PM2.5 concentrations across 138 countries, territories, and regions, utilizing data from over 40,000 air quality monitoring stations.
Introduction
Air pollution, particularly PM2.5, has been linked to various adverse health outcomes, including respiratory and cardiovascular diseases. The WHO recommends an annual average PM2.5 concentration of no more than 5 μg/m³ to mitigate these risks. However, achieving and maintaining this standard remains a challenge for many regions worldwide. The 2024 World Air Quality Report offers an in-depth assessment of global air quality, serving as a crucial tool for understanding and addressing these challenges.
Methodology
The report aggregates data from over 40,000 air quality monitoring stations across 8,954 locations in 138 countries, territories, and regions. These stations are operated by various entities, including governmental bodies, research institutions, non-profit organizations, and citizen scientists. The data were analyzed to determine annual average PM2.5 concentrations, facilitating comparisons against the WHO guidelines.
Results
Global Compliance with WHO Guidelines
Only 17% of global cities met the WHO’s annual average PM2.5 guideline of 5 μg/m³, underscoring the widespread nature of air pollution. Notably, seven countries achieved this standard: Australia, Bahamas, Barbados, Estonia, Grenada, Iceland, and New Zealand.
Most Polluted Countries
The five countries with the highest annual average PM2.5 concentrations were:
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Chad: 91.8 μg/m³, exceeding the WHO guideline by over 18 times.
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Bangladesh: 78.0 μg/m³, more than 15 times higher than the guideline.
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Pakistan: 73.7 μg/m³, over 14 times the recommended limit.
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Democratic Republic of the Congo: 58.2 μg/m³, exceeding the guideline by more than 11 times.
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India: 50.6 μg/m³, over 10 times the WHO guideline.
Regional Pollution Disparities
Central and South Asia emerged as regions with significant pollution challenges. Byrnihat, India, recorded the highest PM2.5 concentration among metropolitan areas at 128.2 μg/m³. Additionally, six of the nine most polluted global cities were located in India.
In Southeast Asia, cities such as Ho Chi Minh City, Phnom Penh, and Bangkok ranked among the world’s top five most polluted cities. Factors contributing to this pollution include crop burning, industrial emissions, and heavy traffic. In response, governments implemented measures like free public transportation and temporary school closures to mitigate exposure.
Air Quality in the United States
Los Angeles, California, was identified as the most polluted major U.S. city, while Ontario, California, ranked as the most polluted city overall in the country. Conversely, Seattle, Washington, emerged as the cleanest major U.S. city. Mayaguez, Puerto Rico, was the cleanest metropolitan area in 2024, with an annual average PM2.5 concentration of 1.1 μg/m³.
Improvements and Data Gaps
Southeast Asia experienced a decrease in PM2.5 concentrations across all countries. However, challenges like transboundary haze and lingering El Niño conditions persist. In Africa, a significant data gap exists, with only one monitoring station available for every 3.7 million people, highlighting the need for expanded monitoring infrastructure.
Impact of Environmental Events
Wildfires in the Amazon rainforest in 2024 had a profound impact on air quality across Latin America. Cities in Brazil’s Rondônia and Acre states experienced PM2.5 levels that quadrupled in September due to these fires.
Cleanest Regions
Oceania emerged as the world’s cleanest region, with 57% of its cities meeting the WHO PM2.5 annual guideline value of 5 μg/m³. Cities like Canberra, Australia, have been recognized for their superior air quality, making them desirable destinations for those seeking cleaner environments
Discussion
The findings from the 2024 World Air Quality Report highlight the persistent challenge of air pollution globally. The limited compliance with WHO guidelines indicates a pressing need for enhanced air quality management strategies. Regions with high pollution levels, such as Central and South Asia, require targeted interventions to reduce emissions from industrial, agricultural, and transportation sources.
The data scarcity in Africa underscores the necessity for investment in air quality monitoring infrastructure to inform policy and protect public health. Furthermore, the impact of environmental events like wildfires emphasizes the interconnectedness of ecological health and air quality, necessitating integrated approaches to environmental management.
Conclusion
Air pollution remains a global health crisis, with the majority of countries failing to meet WHO PM2.5 guidelines. The 2024 World Air Quality Report provides critical insights into the state of global air quality, serving as a foundation for policymakers, researchers, and public health officials to develop and implement strategies aimed at reducing air pollution and mitigating its health impacts.
