Tiny particles of air pollution, far smaller than a human hair, are contributing to nearly two million excess deaths globally each year, according to the most comprehensive study of its kind.
The research, led by scientists from the Max Planck Institute for Chemistry in Germany, has for the first time, mapped exposure to ultrafine particles (UFPs) at a resolution of one square kilometre across the globe. The findings reveal that these invisible pollutants, emitted mainly by combustion sources such as traffic, industry and energy production, pose a major and previously under-recognised threat to public health.
Ultrafine particles measure less than 100 nanometres in diameter, meaning they carry little mass but dominate the number of particles in polluted air. Their size allows them to bypass the body’s respiratory defences, penetrating deep into the lungs and crossing into the bloodstream and brain. This unique ability makes them particularly dangerous for cardiovascular health, with researchers estimating that roughly half of UFP-related deaths are caused by heart conditions.
The study combined satellite data, ground-based measurements and machine learning to produce global exposure estimates. Annual concentrations in urban areas typically range between 10,000 and 30,000 particles per cm³.
In Europe, the average mortality density from UFP exposure stands at 35.7 deaths per 100,000 people annually, while in North America the figure is 27.4 per 100,000. Southern and Eastern Europe record the highest levels, with Greece particularly badly affected.
Globally, the researchers estimate that 1.99 million excess deaths per year are attributable to UFP exposure, representing approximately five per cent of total mortality from non-communicable diseases. The vast majority of this burden – 91% – occurs in urban and suburban areas, with 78% concentrated in densely populated city centres.
The study also attributes UFP exposure to specific sources. In high-income countries, industry accounts for 39% of exposure, fossil energy production for 33%, road traffic for 20%, and domestic energy use for 8%. In low- and middle-income countries, domestic burning of wood and other solid fuels plays a much larger role.
Prof. Dr. Jos Lelieveld, Director emeritus at the Max Planck Institute for Chemistry in Mainz and lead author of the study said: ‘Ultrafine particles are literally a blind spot in air quality policy: they are not covered by any regulation, even though they are ubiquitous in our cities.
‘With our data, we can for the first time show worldwide where exposure is highest and which sources are responsible – above all combustion in traffic, industry and energy production. This gives policymakers a concrete tool to take targeted action.’
The researchers suggest that an annual limit of 5,000 particles per cm³ could reduce global excess mortality by approximately 45%.
With the World Health Organization already classifying UFPs as a contaminant of emerging concern, the study provides compelling evidence that urgent action is needed – particularly in the world’s most polluted cities, where the health of millions hangs in the balance.
Univ-Prof. Dr. Thomas Münzel, Senior professor at the Center for Cardiology at the University Medical Center Mainz said: ‘What is particularly alarming for us in cardiology is that ultrafine particles bypass the body’s natural protective barriers and can reach the bloodstream – and even the brain – directly. In our own work, we see how the cardiovascular system responds to this exposure: with oxidative stress, damaged blood vessels, and an increased risk of heart attack and stroke.
‘Roughly half of the deaths caused by ultrafine particles worldwide are due to cardiovascular disease. That makes one thing clear: clean air is heart health. We urgently need binding limit values and routine monitoring of ultrafine particles, just as we already have for fine particulate matter.’
The full research can be read here.