Overview: Polluted air and a surprising transport route
Scientists have demonstrated, for the first time, how tiny particles in polluted air can hitch a ride on red blood cells and travel throughout the body. The findings, published in ERJ Open Research, show that particles produced by vehicle exhaust and brake or tyre wear can attach to circulating red blood cells. This discovery adds a new dimension to our understanding of how air pollution may reach organs far from the lungs, including the heart and brain, and possibly contribute to disease risk.
What the study did and what was found
The research team, led by Professor Jonathan Grigg and Dr Norrice Liu at Queen Mary University of London, studied 12 healthy adult volunteers. Each participant spent four hours in an office setting, then one hour near a busy central London road, followed by another hour back in the office. An aethalometer measured the ambient particle pollution in the air around them. Eight volunteers repeated the experiment on a separate day wearing an FFP2 mask to test its protective effect.
Blood samples were taken at three moments: after the four hours indoors, immediately after the roadside exposure, and after returning indoors. Using microscopy, scientists quantified how many pollution particles stuck to the volunteers’ red blood cells. Roadside air had nearly five times more particulate matter than the office air, and, on average, the amount of particle material attached to red blood cells rose two to threefold after an hour by the road.
Despite the attachment being a small proportion of red blood cells (about two to three in every thousand), calculations suggested that in a typical 5‑liter circulation, around 80 million red blood cells could be transporting particles after a stay near a main road. In some participants, the particle load decreased after leaving the roadside, while in others it stayed high, hinting at individual differences in the body’s response to pollution exposure.
Evidence beyond humans: lab confirmation
To strengthen their conclusions, researchers exposed human red blood cells and mice to diesel exhaust particles in laboratory conditions. They found particles adhered readily to both human and mouse red blood cells, with more adhesion occurring as particle quantity increased. Analysis of the particles on the blood cells revealed elements associated with vehicle exhaust and brake/tyre wear, including iron, copper, silicon, chromium, and zinc, along with silver, copper, and molybdenum.
Particle size was in the PM2.5 range, which is key for air quality monitoring and health risk assessment. The researchers say the combination of size and chemical makeup aligns with emissions from traffic and related wear and tear on roads.
Masking the exposure: a clear protective signal
The FFP2 mask proved effective in reducing the dose of inhaled particles that could attach to red blood cells. While roadside pollution levels remained the same, the masked volunteers did not show an increase in particles on their red blood cells. This finding suggests masks could be a practical tool to lower bodily exposure to tiny pollution particles, particularly for people with lung disease or those who cannot avoid urban pollution.
What this means for health and policy
These results illuminate a plausible mechanism by which air pollution might reach and affect distant organs, reinforcing concerns about cardiovascular and neurological risks associated with polluted air. The study provides a measurable way to gauge a person’s internal exposure to pollution, which could help researchers identify factors that amplify or mitigate the risk. It also underscores the potential benefit of protective measures, such as properly fitted masks, in urban settings where exposure is unavoidable.
Public health voices, including independent experts not involved in this study, have emphasized the broader need for stronger air quality regulations. Reducing traffic-related pollution could lower the number of particles that reach the bloodstream, potentially reducing risk for susceptible populations and improving overall urban health outcomes.
Limitations and next steps
While the findings are compelling, the study involved a relatively small group of healthy adults. More research is needed to determine how factors such as age, preexisting health conditions, and longer-term exposure affect particle attachment to red blood cells and related health risks. Future work could also explore whether reduction of pollution levels at the source translates into measurable decreases in the number of particles traveling through the bloodstream.
In sum, this study provides a tangible link between what we breathe and what travels inside us, offering a new lens on how air pollution might contribute to disease and how protective measures could mitigate harm.
