An unprecedented study by Monash University has found that 99.82% of the earth’s surface and 99.999% of the world’s population are exposed to risky levels of PM2.5 (very small airborne particles with a diameter of 2.5 micrometers), exceeding the safety levels recommended by the World Health Organization (WHO).
This is due to the lack of air pollution monitoring stations around the world, which has resulted in a lack of data on local, national, regional, and global exposure to these particles.
The study led by Professor Yuming Guo, from Monash University’s School of Public Health and Preventive Medicine, used traditional air quality monitoring observations, meteorological and satellite-based air pollution detectors, and statistical and machine learning methods to more accurately assess PM2.5 concentrations around the world.
The study found that while daily PM2.5 levels have decreased in Europe and North America in the two decades to 2019, levels have increased in South Asia, Australia, New Zealand, Latin America, and the Caribbean, with more than 70% of days globally having levels above what is safe.
The research team also revealed that, according to WHO, only 0.18% of the global land area and 0.001% of the global population were exposed to annual exposure below this guideline limit (annual average of 5 μg/m³) in 2019.
Professor Guo stated that unsafe PM2.5 concentrations also show different seasonal patterns, with eastern areas of northern America having high PM2.5 in their summer months (June, July, and August), and northeastern China and northern India during their winter months (December, January, and February). PM2.5 air pollution was also recorded as relatively high in August and September in South America and from June to September in sub-Saharan Africa.
This study provides an in-depth understanding of the current state of outdoor air pollution, which should motivate governments and international organizations to take action to reduce PM2.5 levels and ensure environmental health security.