Ultrafine air pollution from planes threatens the health of millions

The health of more than 50 million people living within 20 kilometres of the busiest airports in Europe is being harmed by high levels of ultrafine air pollution emitted by jet engines, according to a study commissioned by the campaign group Transport & Environment (T&E).

Some other studies suggest that ultrafine particles can increase the risk of respiratory diseases, cardiovascular diseases, neurological conditions, diabetes and pregnancy issues, says Daan van Seters at consultancy CE Delft in the Netherlands. Based on these studies, his team has now tried to estimate the Europe-wide impact.

However, ultrafine pollution is a little-studied aspect of air pollution and there are big uncertainties. “The research in this area is scarce and evidence is often not conclusive,” says van Seters.

Much research on particulate air pollution has focused on particles smaller than 2.5 micrometres in diameter, known as PM2.5. Ultrafine particles are a subset with a diameter of less than 0.1 micrometres.

“That makes them very dangerous, because, being so small, they can get very, very deep into the human body,” says Carlos López de la Osa at T&E.

Jet engines produce more ultrafine particles than other kinds of engines do, so people living or working near airports are most likely to be exposed to this form of air pollution. However, there are no effective limits on their levels.

While ultrafine particles are a form of PM2.5, the limits for PM2.5 are for the total mass of particles per cubic metre of air. Because ultrafine particles are so small, there can be huge numbers per cubic metre without exceeding PM2.5 limits.

In fact, there is very little monitoring of the levels of ultrafine particles at all, says López de la Osa. “What we have is mostly local studies around individual airports: Zurich, Amsterdam, Berlin, Los Angeles,” he says. “We don’t have a comprehensive view. That’s one of the main reasons why we decided to launch this study.”

To estimate the Europe-wide impact, van Seters and his colleagues first estimated the levels of ultrafine pollution around the continent’s 32 busiest airports, based on numbers from the studies of individual airports. The team assumed that ultrafine pollution rises linearly with the number of flights and didn’t consider wind patterns.

Next, based on studies looking at its health impacts, the researchers estimated that ultrafine pollution near the 32 airports has caused an extra 280,000 cases of high blood pressure, 330,000 cases of diabetes and 18,000 cases of dementia over the years.

“This is a first-order estimation based on extrapolation, and epidemiological research should be done to get more precise estimations,” says van Seters.

But he thinks that, if anything, it is an underestimate. That is because the study looks only at 32 airports and only at people living within 20 kilometres, plus it excludes those working at airports.

In terms of exposed populations, Orly Airport near Paris tops the list, with more 6 million people living within 20 kilometres of it. London’s Heathrow Airport is fourth, with more than 3 million people nearby.

The team’s estimate of the health impacts relies heavily on a 2022 study of Schiphol airport near Amsterdam by Nicole Janssen at the National Institute for Public Health and the Environment in the Netherlands and her colleagues. Janssen says her team was contacted by CE Delft, but advised the researchers against trying to quantify the impacts in this way given the large uncertainties.

However, she agrees that more research is needed. “We would like to stress our recommendation to further investigate the risk of ultrafine particles from aviation around other international airports,” says Janssen.

There are several ways of reducing ultrafine pollution levels, says Krisztina Toth at T&E. It is possible to modify jet fuels – for instance, by reducing the sulphur content – to reduce ultrafine particle emissions. So-called “sustainable aviation fuels” (SAF) also produce less ultrafine pollution.

“But we know unfortunately that it takes quite a while before the SAF production scales up enough so that it can have that impact,” says Toth.

Limiting airport expansion and flight numbers, and encouraging alternative forms of transport, would help – and also limit the climate impacts of flying.