Pollution particles hitch a ride inside the body
A new study published in ERJ Open Research provides the first direct evidence that tiny air pollution particles can adhere to red blood cells, hitching a ride as they circulate through the body. The work from Queen Mary University of London involved 12 healthy adult volunteers who spent time near a busy London road after four hours working in an office.
How the study was conducted
Each participant carried an aethalometer to measure ambient particle levels during three phases: four hours in an office, one hour by the roadside, and one hour back in the office. Blood samples were taken at each phase and examined under microscopes to quantify particles attached to red blood cells.
Eight of the volunteers were re-tested on another day, this time wearing an FFP2 mask. Roadside pollution levels were roughly five times higher than in the office, according to the devices used.
Key findings
Participants showed an increase in particles stuck to red blood cells after roadside exposure. On average, two to three times as many particles attached to red blood cells after the roadside period. In some people levels fell after moving away; in others, they remained high, suggesting individual differences in how the body handles inhaled pollution.
Even though a small fraction of red blood cells carried particles (about two to three per thousand), the researchers estimate that about 80 million red blood cells in five litres of blood could be transporting particles after a short roadside exposure.
Protective effects of masks and broader implications
When volunteers wore an FFP2 mask, their RBC-bound particle load did not rise after roadside exposure, indicating masks can markedly reduce particle dose reaching the blood. The team also exposed human red blood cells and mice to diesel exhaust in the lab, confirming that particles readily attach to blood cells in both species and that more particles lead to more attachment.
What the particles contain
Analyses showed the attached particles contained elements linked to vehicle exhaust and brake/tyre wear, including iron, copper, silicon, chromium, zinc, silver, copper, and molybdenum. The particles were PM2.5 in size, well within the range used to monitor air pollution risks.
Why this matters for health and policy
Experts say red blood cells carry oxygen around the body, and the study demonstrates a plausible route by which pollution can reach organs such as the heart and brain. The findings underscore the need for robust pollution-control measures and highlight the potential value of protective masks for vulnerable populations and people unable to avoid traffic exposure.
Expert perspectives
Independent commentator Dr Ane Johannessen notes that while many people cannot avoid traffic-related pollution, reducing exposure and improving air quality could lower risk. She cautions that public health policy must balance practical protections with strong environmental regulations to reduce overall pollution.
