In a recent study, a team of scientists led by Monash University in Australia has found that only 0.18 percent of the global land area and 0.001 percent of the world’s population are exposed to levels of fine particulate matter (PM2.5) deemed safe by the World Health Organization (WHO). While daily levels of these dangerous pollutants have reduced in Europe and North America during the two decades to 2019, in Australia, New Zealand, Southern Asia, Latin America, and the Caribbean they have increased, with over 70 percent of days globally witnessing potentially hazardous levels.
The experts combined traditional air quality monitoring observations, satellite-based meteorological and air pollution detectors, and statistical and machine learning methods to more accurately assess PM2.5 concentrations worldwide.
“In this study, we used an innovative machine learning approach to integrate multiple meteorological and geological information to estimate the global surface-level daily PM2.5 concentrations at a high spatial resolution of approximately 10km ×10km for global grid cells in 2000-2019, focusing on areas above 15 μg/m³, which is considered the safe limit by WHO (the threshold is still arguable),” explained senior author Yuming Guo, a professor of Global Environmental Health and Biostatistics at Monash.
The analysis revealed that, regardless of a slight decrease in high PM2.5 days globally, over 70 percent of days still had PM2.5 concentrations higher than 15 μg/m³ by 2019, with areas in southern and eastern Asia witnessing such dangerous concentrations in more than 90 percent of days.
While the annual average concentration between 2000 and 2019 was 32.8 µg/m3 globally, the highest concentrations were found in eastern Asia (50.0 µg/m3), southern Asia (37.2 µg/m3), and northern Africa (30.1 µg/m3), and the lowest ones in Australia and New Zealand (8.5 μg/m³), Oceania (12.6 μg/m³), and southern America (15.6 μg/m³).
The researchers also discovered that unsafe PM2.5 concentrations exhibited different seasonal patterns, with northeast China and north India facing high concentrations in winter, and eastern areas in northern America being exposed to more air pollution in summer.
According to Professor Guo, this study is important since it provides a deep understanding of the current state of outdoor air pollution and its possible impacts on human health. “With this information, policymakers, public health officials, and researchers can better assess the short-term and long-term health effects of air pollution and develop air pollution mitigation strategies,” he concluded.
The study is published in the journal The Lancet Planetary Health.
By Andrei Ionescu, Earth.com Staff Writer
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