By 2019, more than 70 percent of days in a year had particulate matter concentrations higher than 15 μg/m³ which is the safety threshold set by the WHO

A world first study of daily ambient fine particulate matter across the globe has found that almost nowhere on the earth is safe from air pollution.

The study led by researchers at Monash University in Australia reveals that only 0.18 percent of the global land area and 0.001 percent of the global population are exposed to levels of fine particulate matter (PM2.5) below levels of safety recommended by the World Health Organization (WHO).

While daily levels have reduced in Europe and North America in the two decades to 2019, they have increased in Southern Asia, Australia, New Zealand, Latin America and the Caribbean, states the study published in the prestigious journal, Lancet Planetary Health.

The study has also provided a map of how PM2.5 has changed across the globe in the past decades.

PM2.5 are fine, inhalable particles, with diameters that are generally 2.5 micrometers and smaller. Of all the common air pollutants, PM2.5 is associated with the greatest proportion of adverse health effects, both in the United States and world-wide based on the World Health Organization’s Global Burden of Disease Project.

Exposure to PM2.5 over a long period of time has been found to be associated with premature death, especially in individuals with chronic heart or lung diseases, as well as reduced lung function growth in children.

Particulate matter also reduces visibility, promotes climate warming and alters plant growth and yield.

Insufficient pollution monitoring stations around the world have led to a lack of information about the levels of local, national, regional, and global exposure to PM2.5.

“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,” senior researcher, Professor Yuming Guo, said.

The study further finds that by 2019, more than 70 percent of days in a year had PM2.5 concentrations higher than 15 μg/m³ which is the safety threshold set by WHO for daily PM2.5 exposure.

In southern Asia and eastern Asia, more than 90 percent of days had daily PM2.5 concentrations higher than 15 μg/m³ during the year. Australia and New Zealand also had a marked increase in the number of days with high PM2.5 concentrations.

The study also showed that the average annual PM2.5 level worldwide from 2000 to 2019 was 32.8 μg/m³.

The highest PM2.5 concentrations were 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).

“The study provides a deep understanding of the current state of outdoor air pollution and its impacts on human health,” Professor Guo said. “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.”

Also Read: How to protect yourself from air pollution? – In Conversation with Dr. Chandrakant Lahariya