Not Fine with Ultrafine: Airplane pollution comes from engine lube, not just burned fuel

I first dedicated a neuron to “ultrafine particles” (UFPs) around a decade ago, when I was looking into the health problems associated with the air that I, personally, was breathing. At the time I had just moved to an apartment a couple blocks southwest of Interstate 93, one of Boston’s biggest freeways. I knew that air pollution was harmful, but if memory serves, I was only just starting to learn how that harm actually manifests in the people exposed. In digging up information for this post, I came to the conclusion that the simplest way to describe the effects is that your health will just… be a bit worse. All of your health. It basically puts a cap on how healthy you, personally, can actually be. If you do everything right, you’ll still be less healthy, more vulnerable to chronic conditions, and more vulnerable to heart attacks and strokes. Or, to quote a study from Tufts, living near a highway can be bad for your health in a million small ways:

Fine and ultrafine particulates both cause cardiovascular disease in similar ways. Once they hit your lungs, your body immediately recognizes that something is amiss. “It essentially says, ‘Oh, crap, something’s wrong here,’ and releases cytokines, molecules that control immune response,” says David Weiss, M12, who works on the CAFEH study analyzing health surveys generated as part of the community outreach component of the research project. Those cytokines are used to summon help to the site of the infection, but also affect the activity of the immune system throughout the body.

Weiss likens the body’s reaction to the terror-alert system that was put into place after 9/11. “You know, the one that was green, yellow, red,” he says. “The higher levels of cytokines will take you from a level green to a level yellow.” In other words, your whole body goes on high alert, causing elevated levels of inflammation.

Of course, not all inflammation is bad, says Doug Brugge. For example, if you cut your finger, within a day, you’ll see some inflammation (redness) around the cut as your immune system mobilizes to kill any invading bacteria. “That is an example of a good inflammatory response, because it’s localized,” says Brugge. “It’s responding to a real problem, and it’s controlled. It has a beginning and an end.”

But constant exposure to fine and ultrafine particulate pollution can cause chronic inflammation. If that happens, white blood cells called macrophages, which are part of the body’s natural defense mechanism, go into overdrive, seeking out bacteria or other foreign objects in the bloodstream. They start attacking whatever’s there with extra gusto—including certain types of cholesterol that accumulate in the bloodstream. As macrophages gorge themselves on this fatty molecule, they (and their cholesterol contents) settle into the inner lining of blood vessels, where they slowly build up and create artery-clogging plaques.

Weiss says that some of these deposits may happen anyway as the body ages, but inflammation caused by particulate pollution speeds the process, leading to premature heart attacks and strokes.


Essentially, Weiss says, this gives the pollutants that make up ultrafine particles more bang for their buck. They’re more potent than larger particles, so they may lead more quickly to heart disease. And, he adds, they may be small enough to get directly into the bloodstream, where they can do even more damage.

“Larger particles can’t cross the barrier from the lungs to the bloodstream,” says Weiss, “but the ultrafine particles can. So because of that, and partly because of their increased exposed surface area, there’s more of an opportunity for them to have reactions that will cause inflammation.” The only way to avoid this inflammation—short of somehow removing particles from the air around you—is to spend less time near major highways.

“For people who move away from the highway, it’s like they quit smoking,” says Wig Zamore, a longtime resident of Somerville with a master’s degree in urban planning. Over the past decade, Zamore has worked with community groups on public health and clean-air issues, and is a member of the CAFEH steering committee, a group of academics and community members who help guide the study’s research.

“Their risk pretty immediately starts to go down, and for the people who move closer to a highway, their risk immediately starts to go up over a matter of just a couple years,” he says, citing a 2009 study by the University of British Columbia.

The problem is, of course, that many people living near highways don’t have the financial means to move. According to Zamore, of the 35 million Americans who live by a major four-lane highway, roughly 18 percent are renters or live in low-income housing.

We were living there because of the low rent – my flat farther away from I-93 had its rent go up by something like $150/month, so we had to move, and there didn’t seem to be anything of a comparable price that didn’t come with at least as much air pollution. It should not surprise you to learn that that neighborhood, like most high-pollution neighborhoods in the US, was mostly not white. Unfortunately, the dangers of UFPs go beyond this smoking-like effect on those most exposed. Infant exposure has been linked to adult lung disease, implying lifelong problems, and exposure in utero has been linked to childhood asthma.

But wait! There’s more!

See, as previously mentioned, the real problem with UFPs is that they’re so small. They’re smaller than our body is really capable of dealing with in a meaningful way. To my knowledge, we don’t currently know the exact causal chain from UFP exposure in pregnant mothers to asthma in preschool. It could be that the aforementioned inflammation is what’s actually affecting lung development, but it’s also possible that the particles are simply passing through the mother into the fetus, especially since there’s evidence that they also cross the blood/brain barrier. Unsurprisingly, scientists are looking into possible links to neurological problems.

There’s a great deal more such research out there, but I think this is enough to get across why I think that UFPs are something we should take seriously. The fact that a lot of them seem to come from car tires, rather than exhaust, is one reason that I think we should be moving away from cars as a primary mode of transit, even without their greenhouse gas emissions. If I snapped my fingers and made every car in the world electric, Somerville would still be having problems. If we manage to build a system that’s not obsessed with profit and growth, I think there will be a lot less need for people to be moving around so much. A shorter work week, for example, would mean less commuting, and more work could be done from home. That, combined with increased investment in mass transit, and the reclamation of urban landscapes for people, rather than cars, could largely eliminate traffic as we know it today.

Unfortunately, that’s not the only big source of UFPs. For the sake of this exercise, we’ll pretend that coal plants went away with the gas-powered cars, and were replaced with insert favorite power source here. We also need to reduce air traffic, and as with cars, focusing just on the fuel would be a mistake. It turns out that jet engines – specifically the oils that lubricate them – are a major source:

Since several years, the Hessian Agency for Nature Conservation, Environment and Geology (HLNUG) has been measuring the number and size of ultrafine particles at various air monitoring stations in the vicinity of Frankfurt International Airport, for example in the Frankfurt suburb of Schwanheim and in Raunheim. Last year, scientists led by Professor Alexander Vogel at Goethe University Frankfurt analysed the chemical composition of the ultrafine particles and came across a group of organic compounds which, according to their chemical fingerprints, originated from aircraft lubrication oils.

The research team has now corroborated this finding by means of further chemical measurements of the ultrafine particles: the particles originated to a significant degree from synthetic jet oils and were particularly prevalent in the smallest particle classes, i.e. particles 10 to 18 nanometres in size. Such lubrication oils can enter the exhaust plume of an aircraft’s engines, for example through vents where nanometre-sized oil droplets and gaseous oil vapours are not fully retained.

In laboratory experiments, the researchers also succeeded in reproducing the formation of ultrafine particles from lubrication oils. To this end, a common engine lubrication oil was first evaporated at around 300 °C in a hot gas stream, which simulated the exhaust plume of an aircraft engine, and subsequently cooled down. The number-size distribution of the freshly formed particles was then measured.

Alexander Vogel, Professor for Atmospheric Environmental Analytics at the Institute for Atmospheric and Environmental Sciences of Goethe University Frankfurt, explains: “When the oil vapour cools down, the gaseous synthetic esters are supersaturated and form the nuclei for new particles that can then grow fast to around 10 nanometres in size. These particles, as our experiments indicate, constitute a large fraction of the ultrafine particles produced by aircraft engines. The previous assumption that ultrafine particles originate primarily from sulphur and aromatic compounds in kerosene is evidently incomplete. According to our findings, lowering lubrication oil emissions from jet engines holds significant potential for reducing ultrafine particles.”

The experiments show that the formation of ultrafine particles in jet engines is not confined to the combustion of kerosene alone. Potential mitigation measures should take this into consideration. This means that using low-sulphur kerosene or switching to sustainable aviation fuel cannot eliminate all the pollution caused by ultrafine particles.

I think it’s important to be clear here – I don’t think we should be focused on the total elimination of all ultrafine particle sources. It’s a nice idea in theory, but so long as we want to keep the benefits of modern engines of any sort, there’s a good chance we’ll be producing some form of harmful air pollution. What I do want is to drastically reduce the amount we generate, even as we develop things like plant-based jet fuel. As with cars, I think that changing our economy would drastically reduce air travel (it’s almost like I’m obsessed with systemic change. Funny, that), but I also think that it would open up options for slower forms of air travel, like lighter-than-air craft, that don’t require the same kind of heat and friction involved in getting airplanes off the ground.

I also – since it’s a factor we shouldn’t forget – believe that a post-capitalist society would greatly reduce the amount of pollution generated by military activity.

Pollution will probably always be something we have to manage, rather than entirely eliminate, but as we’re all aware by now, we generate far, far more pollution than is required for humanity to have a good standard of living, complete with the benefits of technology. I wish it was as easy as swapping out our fuel sources, as difficult a task as that is. Unfortunately, it keeps coming back to the need for systemic change. Capitalism and imperialism are not the only source of problems in society, but the problems they’re creating have become so big that it’s often hard to even tell what those other problems might be. It’s like worrying about wet feet when you’ve fallen overboard at sea. In the meantime, while there’s no practical way to entirely protect yourself, there’s some evidence that having plants around can help, so support efforts to increase the amount of greenery in cities, and “green walls” around places like airports and freeways. There are plenty of other benefits to doing that, and I really do believe that any steps we take to strengthen people, including literally caring for their health, will bring that systemic change just a little bit more within our reach.

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  1. Katydid says

    FAA Outage in the USA meant that planes were grounded today until 9 am. I work near a flightpath for the major airport near me. The quiet was refreshing. It reminded me of the early days of the pandemic when few flights were running, and also 9/11, when planes were grounded for several days.

    The noise pollution of airplanes is yet another form of pollution.

  2. says

    @Marcus – *until we bring back asbestos

    @Katydid – yeah, I’d like to see us deal with noise and light pollution. I always get a little sad when I’m out in the middle of the night and there’s a bird singing because it thinks it’s dawn.

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