Ultrafine Particle Levels Spike Inside Aircraft Cabins

Passengers on commercial flights may be exposed to concentrations of ultrafine particles (UFPs) more than twice what the World Health Organization (WHO) considers high during boarding, taxiing and landing, according to recent scientific studies that are drawing attention to a largely unregulated air quality risk in aviation.

Research published in Environment International and reported by The Guardian found that UFP concentrations inside aircraft cabins can exceed elevated urban levels during ground operations and low-altitude phases of flight. Because of their extremely small size, UFPs can bypass the respiratory system’s natural defenses and enter the bloodstream, making them a potential health risk despite often going unnoticed.

Following these findings, researchers from Université Paris Cité measured air quality on board commercial flights operated by a French airline departing from Charles de Gaulle Airport to various European destinations. Portable pollution sensors were discreetly placed in empty seats or service areas to record the air passengers actually breathe throughout all phases of the journey, from boarding to landing.

The data showed clear variations in UFP concentrations depending on the phase of flight. During cruise, when aircraft are at high altitude and away from direct pollution sources, UFP levels inside the cabin were low and the air was relatively clean due to filtered outside air.

The situation changed significantly on the ground. During boarding and taxiing, UFP concentrations surged, reaching on average more than double what the WHO considers a high level, even though that threshold is not yet part of formal regulation. Concentrations rose again during approach and landing, likely due to proximity to operating engines, active runways and airflows carrying emissions from the airport environment.

Researchers observed that this pattern was consistent across departure and arrival airports, suggesting that elevated exposure is not linked to a single location or isolated event. In addition to UFPs, the study measured black carbon, a pollutant associated with soot from incomplete combustion, mainly from diesel engines and jet fuel. Black carbon concentrations also peaked when aircraft were operating in airport environments.

Previous studies have linked repeated exposure to ultrafine particles to lung inflammation, oxidative stress and cardiovascular effects. The WHO and the Health Council of the Netherlands warned in 2021 of growing evidence connecting UFP exposure to pulmonary inflammation, cardiovascular alterations, hypertension and fetal development issues.

At the time, the WHO did not establish an official exposure threshold, citing methodological differences across studies rather than a lack of evidence. Since then, large-scale research has strengthened the link between chronic exposure to ultrafine particles and premature mortality, including lung cancer, as shown in a study involving nearly 11 million people in the Netherlands.

Because the highest exposure levels occur when passengers are seated and unable to reduce their exposure, during boarding, taxiing and landing, researchers describe the aircraft cabin as a microenvironment of particular public health interest.

The impact of ultrafine particles extends beyond aircraft interiors. Environmental chemistry studies show that aviation emissions contribute significantly to air pollution around airports, affecting workers and nearby communities.

Measurements cited in the research detected particles generated at Charles de Gaulle Airport more than five kilometers away. At one kilometer from the airport, concentrations were comparable to those measured alongside Paris’ busiest ring road. Similar findings in London indicate that Heathrow Airport influences air quality across large areas of western and central parts of the city.

WHO has identified ultrafine particles as an emerging pollutant of high public health concern and has called for improved monitoring, research and regulatory frameworks. Environmental health experts say measures such as electrifying ground equipment, reducing the use of auxiliary power units and implementing continuous air quality monitoring could significantly reduce exposure.

Without clearer regulations and greater transparency for passengers, researchers warn that ultrafine particle pollution in aviation will remain an invisible risk, despite mounting scientific evidence of its potential health effects.