Unlike fine particulate matter (PM2.5), which is subject to legal limits in the EU and the US, ultrafine particles remain unregulated. Though they contribute little to particulate mass, their small size gives them a large surface area relative to their mass, letting them penetrate deep into the lungs, bypass respiratory defenses, and reach the bloodstream — and, via the olfactory pathway through the nose, the brain directly.

A Global Exposure Map at 1-Kilometre Resolution

An international team led by Prof. Jos Lelieveld of the Max Planck Institute for Chemistry and the Cyprus Institute combined satellite data, land-use information, and measurements from 155 locations worldwide with machine learning to map long-term exposure to ultrafine particles at a resolution of one kilometre for the first time, covering 2010 to 2019. Annual mean concentrations in cities typically range between 10,000 and 30,000 particles per cubic centimetre.

The researchers present a 95% confidence interval for their estimate of 1.99 million premature deaths, indicating 95% certainty that the true toll falls between 0.81 million and 3.89 million. Using a meta-analysis of large cohort studies from Europe and North America, they derived a mortality density of 35.7 per 100,000 people per year in Europe and 27.4 per 100,000 in North America, with exposure and mortality particularly high in Southern and Eastern Europe. Globally, about 91 percent of ultrafine-particle-related excess deaths occur in urban and suburban areas.

“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,” said Lelieveld.

A Particular Danger to the Cardiovascular System

The study highlights ultrafine particles as an underrecognized cardiovascular risk factor. They can cross the lungs into the bloodstream, trigger systemic oxidative stress and endothelial dysfunction, promote atherosclerosis, and are linked to hypertension, diabetes, heart failure, myocardial infarction, and impaired coronary microcirculation. “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,” said Univ.-Prof. Dr. Thomas Münzel.

According to the researchers, ultrafine particles in polluted regions consist mainly of black and organic carbon from combustion. Globally, around 75 percent of exposure originates from fossil fuels, rising to over 90 percent in high-income countries, while domestic wood burning plays a significant role in lower-income countries. The study found that an annual limit value of 5,000 particles per cubic centimetre could reduce global excess mortality from ultrafine particles by around 45 percent.

Journal: Cardiovascular Research
DOI: 10.1093/cvr/cvag136
Article Title: Air quality and health implications of exposure to ultrafine particle pollution
Publication Date: July 14, 2026

Source: EurekAlert