Only 0.001% of the global population were exposed to exposure lower than the recommended limit.
Air pollution is not only insidious but also ubiquitous and practically nowhere on earth is free from some degree of airborne particles, according to scientists.
A team of researchers, led by Prof. Yuming Guo from the Monash University School of Public Health and Preventive Medicine, has reached this conclusion by mapping the shifting levels of PM2.5 particles worldwide since 2000 with the help of air-quality monitoring observations, satellite-based meteorological data and air pollution detectors.
They also employed an innovative machine-learning approach to integrate various meteorological and geological date to estimate the daily PM2.5 concentrations at surface level globally between 2000 and 2019.
While daily levels of air pollution generally subsided in Europe and North America in the two decades, levels have increased in Southern Asia, Australia, New Zealand, Latin America and the Caribbean, the researchers have found. Overall, more than 70% of days in a year globally have levels above what is deemed safe for health with PM2.5 concentrations higher than 15 μg/m³, they report.
“In southern Asia and eastern Asia, more than 90% of days had daily PM2.5 concentrations higher than 15 μg/m³,” note the scientists behind the study. “Australia and New Zealand had a marked increase in the number of days with high PM2.5 concentrations in 2019.”
At the same time, the annual average PM2.5 from 2000 to 2019 was 32.8 µg/m3 with the highest PM2.5 concentrations distributed in the regions of Eastern Asia (50.0 µg/m3) and Southern Asia (37.2 µg/m3), followed by northern Africa (30.1 µg/m3).
This is cause for concern because “only 0.18% of the global land area and 0.001% of the global population were exposed to an annual exposure lower than this guideline limit (annual average of 5 μg/m³) in 2019,” the scientists say.
These findings add to the mounting evidence that air pollution has reached endemic proportions, which is a great concern as long-term exposure to even relatively low levels of PM2.5 pollutants can cause or worsen a variety of diseases in people of all ages. Each year millions of people die of conditions related to air pollution.
Levels of air pollution can vary throughout the year in specific areas, which can influence seasonal health-related issues. In their study Guo and his colleagues found that unsafe PM2.5 concentrations show different seasonal patterns with Northeast China and North India experiencing the highest levels during winter months from December to February. In the eastern areas of Northern America, meanwhile, especially high PM2.5 levels tend to occur in the summer from June to August.
These findings, Guo says, can assist policymakers, public health officials and researchers in assessing the short-term and long-term health effects of air pollution and developing air pollution mitigation strategies accordingly.