MELBOURNE, Australia — Virtually no place on Earth is safe from harmful levels of air pollution, a new study warns. In fact, researchers in Australia say only 0.001 percent of the global population live in areas where levels are below those recommended by the World Health Organization. Toxic particles coming from traffic and industry are the leading environmental risk factor for disease.
Less than a fiftieth the width of a human hair, fine particulate matter (PM2.5) gets into the blood through the lungs, triggering inflammation. The first study of its kind also finds that 0.18 percent of global land areas are still within safe limits.
“It provides a deep understanding of the current state of outdoor air pollution and its 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,” says lead author Professor Yuming Guo of Monash University in a media release.
The international team looked at PM2.5s produced by diesel fumes, wood smoke, brake pads, tires, and road dust. WHO guidelines state that these levels should not exceed 15 micrograms per cubic meter (μg/m³). Prof. Guo and the team mapped changes in concentrations across the world over the past two decades.
“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),” Prof. Guo explains.
The findings fill an important gap in pollution research. Having only a small number of monitoring stations globally has meant information on local, national, regional, and global exposure has been lacking. The findings are based on air quality observations and data from satellite-based weather and pollution scanners and AI (artificial intelligence) neural networks.
Over this study period, the annual average of PM2.5s was 32.8 µg/m3 — over twice the legal limit. High exposure days in Europe and the U.S. fell, but rose in southern Asia, Australia, New Zealand, Latin America, and the Caribbean. By 2019, PM2.5s were above 15 μg/m³ 70 percent of the time — soaring to over 90 percent in southern and eastern Asia.
The highest concentrations were in Eastern Asia (50.0 µg/m3), Southern Asia (37.2 µg/m3), and northern Africa (30.1 µg/m3). The analysis, published in The Lancet Planetary Health, also identified alarming seasonal patterns. For instance, Northeast China and North India had unsafe levels during their winter months of December, January, and February, while eastern areas of northern America were the worst in the summer months of June, July, and August.
“We also recorded relatively high PM2.5 air pollution in August and September in South America and from June to September in sub-Saharan Africa,” Prof. Guo adds.
Australia and New Zealand (8.5 μg/m³), other regions in Oceania (12.6), and South America (15.6) had the lowest annual concentrations of air pollution. Recently, a study found even PM2.5 exposures of between 12.0 and 13.9 μg/m³ raises the risk of dying from cardiovascular disease by 16 percent.
Scientists in the U.S. called for a new standard limit of eight μg/m³. Air pollution kills an estimated 1.8 million people across the world each year. It is also behind nearly two million cases of childhood asthma. In 2013, officials with the International Agency for Research on Cancer classified PM2.5s as a carcinogen.
South West News Service writer Mark Waghorn contributed to this report.