Sitting or working in a plane is not without previously unseen potential health hazards.

We buckle our seatbelts, stow our carry-ons, and settle in for another flight without giving much thought to what we’re breathing. After all, air travel feels routine now. But recent research has uncovered something most passengers never consider: the invisible pollution floating through aircraft cabins during certain phases of flight.

A team of French researchers recently measured ultrafine particles and black carbon inside commercial aircraft flying across Europe, and what they found matters to anyone who flies regularly, especially to flight attendants who spend their working lives in the air. These microscopic pollutants don’t just affect passengers during their occasional trips. They represent a workplace exposure issue for aviation workers and a public health question that deserves our attention.

I know of an airline stewardess who has been flying international flights for years and, just a few years ago, was diagnosed with a brain tumor that needed to be removed. Not only did they have to remove the tumor, but they also had to remove a portion of her skull, wait for the healing to take place, and then replace the skull. I don’t know what the prognosis is for her, but she continues to fly.

If you research the incidence of exposure to radiation in air travel, you might be surprised by how much exposure frequent fliers or air-travel personnel receive. “The World Health Organization (WHO) International Agency for Research on Cancer (IARC) says that ionizing radiation causes cancer in humans…For flight attendants, a NIOSH study found that exposure to 0.36 millisieverts (mSv) or more of cosmic radiation in the first trimester may be linked to increased risk of miscarriage.”

What We’re Actually Breathing Up There

The Paris-aircraft study tracked pollution levels from the moment passengers began boarding until the last person stepped off the plane. Researchers installed specialized monitoring equipment in the cabins of 16 European flights to measure two pollutants: ultrafine particles and black carbon. Ultrafine particles are so small that a hundred of them lined up would barely span the width of a human hair.

Black carbon comes primarily from incomplete combustion, the sooty residue of burning fuel. Have you ever been inside an airline terminal near the plane entrance ramps and smelled the fuel? I know I have, and I wondered why it was coming into the passenger boarding area at the airport. To me, it could not have been healthy.

The results of the French study showed clear patterns that repeat on every flight. When passengers board and when planes taxi across the tarmac, pollution levels spike. During these ground phases, researchers measured an average of 22,784 particles per cubic centimeter during boarding and 20,964 particles during taxi-out.

These numbers might not mean much at first glance, but the World Health Organization recently provided context that makes them significant. WHO guidelines define “high” ultrafine particle exposure as anything above 10,000 particles per cubic centimeter for a twenty-four-hour average, or above 20,000 particles for a single hour.

Once planes climb to cruising altitude, the story changes dramatically. Up where the air is thin and clean, pollution levels drop to just 495 particles per cubic centimeter during the cruise. The aircraft’s ventilation system cycles fresh outside air through the cabin about twenty times each hour, gradually replacing the polluted airport air with cleaner high-altitude air.

Much of the air quality depends on the efficiency of the filtering systems used. It’s actually one of the more well-ventilated indoor spaces you’ll encounter, at least once you’re airborne. Not everyone agrees that this is the way airplanes are making clean air available to passengers and crew. The Association of Flight Attendants has listed its concerns on its website.

But then comes descent and landing, when pollution levels rise again. As planes approach airports, they’re descending into the same polluted air that surrounds every major airport, where jet engines, ground vehicles, baggage tractors, and fuel trucks all contribute to the local air quality problem. We’ve all experienced the sensation of the wheels meeting the runway on landing, and we have seen smoke or mist rising from the wheels, depending on how fast the plane has landed.

Where This Pollution Actually Comes From

Here’s what surprised the researchers: most of the pollution inside aircraft cabins doesn’t come from inside the plane at all. It comes from outside, from the airport environment itself. Airports exist in a bubble of their own pollution. Jet engines idling at gates, diesel-powered ground support equipment moving bags and fuel, brake dust from landing aircraft, and regular road traffic around the airport all contribute to what passengers breathe while on the ground.

When you’re sitting in your seat during boarding, the plane’s doors stand open to the airport environment. All that polluted air flows right in. During taxiing, the aircraft’s environmental control system pulls in outside air to ventilate the cabin, and that outside air carries whatever pollution exists around the airport that day. The research found that longer taxi times meant higher pollution exposure, which makes sense when you consider that every extra minute spent taxiing is another minute drawing polluted airport air into the cabin.

The type of aircraft matters too. Older Airbus models showed higher ultrafine particle levels during climb and descent compared to newer aircraft like the Airbus A220. This probably reflects improvements in engine design and ventilation systems over time. The number of passengers on board also influenced pollution levels, with more passengers correlating to higher black carbon concentrations during cruise and descent, possibly due to increased fuel consumption from the extra weight.

Putting the Risk in Perspective

Before anyone cancels their vacation plans, it’s important to understand where aircraft cabin air quality fits in the bigger picture of pollution exposure. The same research team compared their aircraft measurements to pollution levels in other transportation environments. What they found might surprise you: cabin air during flights showed much lower concentrations than Paris taxis or subway cars. Parisian taxis averaged 27,900 particles per cubic centimeter, and the Paris metro reached even higher levels of black carbon exposure.

This doesn’t mean cabin air pollution isn’t worth addressing. It just means we need to think proportionately. For occasional travelers, the brief periods of elevated exposure during boarding and taxiing probably don’t represent a significant health risk, especially compared to the pollution they might breathe while walking down a city street or commuting in traffic.

But flight attendants face a different situation entirely. They work multiple flights daily, experiencing those boarding and taxiing pollution spikes over and over throughout their careers. For them, this represents genuine occupational exposure that deserves further study and potentially workplace protections.

Around major airports, the situation extends beyond the aircraft themselves. Separate research has shown that approximately fifty-two million Europeans live within twenty kilometers of major airports, constantly exposed to ultrafine particles from aviation activities. These aren’t people who chose to work in aviation or who get to enjoy the benefits of air travel. They’re families who happen to live near airports, often in lower-income communities where housing costs less precisely because of airport proximity.

The health implications of long-term ultrafine particle exposure are still being understood. Still, the evidence suggests that these tiny particles can reach deep into our lungs and even enter our bloodstream. Studies have linked ultrafine particle exposure to respiratory problems, cardiovascular effects, and potentially even neurological conditions. A significant study in the Netherlands found associations between years of ultrafine particle exposure and increased mortality rates, including from lung cancer.

The aviation industry has made remarkable progress in reducing many forms of pollution from aircraft. Engines have become more efficient, fuel consumption has dropped, and emissions of many regulated pollutants have decreased over time. But ultrafine particles and black carbon haven’t received the same regulatory attention, partly because they’re harder to measure and partly because we’re still learning about their health effects (2). The WHO only recently published guidelines for ultrafine particle exposure in 2021, giving regulators and industry something concrete to work toward.

Moving forward, several approaches could help reduce these exposures. Better airport air quality overall would benefit everyone, from passengers to workers to nearby communities. This could mean transitioning ground support vehicles to electric power, improving ventilation in terminal areas, and perhaps even requiring aircraft to use ground power instead of running engines while parked at gates. Newer aircraft designs with improved air filtration systems could also make a difference, as could operational changes like minimizing taxi times when possible.

For now, passengers can take small steps to reduce their own exposure. Getting to your seat quickly during boarding limits your time breathing the most polluted cabin air. Staying seated during taxi rather than standing in the aisle keeps you away from areas where pollutants might concentrate. These aren’t major interventions, but they’re simple choices that cost nothing and might matter on the margins.

The bigger conversation needs to happen at the industry and regulatory levels, where decisions about aircraft design, airport operations, and air quality standards are made. This research gives us better information than we’ve ever had before about what’s actually happening inside aircraft cabins. Now the question becomes what we choose to do with that knowledge.