Kent Palosaari’s persistent cough started eight years after he moved to a rambler on a hill half a mile from Seattle-Tacoma International Airport.

“When I’d go in to talk to the doctors, they’d ask, ‘Are you sure you don’t smoke?'” he said. “No, I don’t. I’m not around smokers. They were confused about why I was getting sick.”

Palosaari said he believes a new study from the University of Washington, funded by the state, may bear some clues to the cause of his illness.

It also makes him worry about his two young children’s health, he said.

The UW researchers found plane emissions are polluting communities near the airport with a particularly worrisome type of “ultrafine” particles.

Ultrafine particles are less than 100 nanometers in diameter — one one-thousandth the width of a human hair — and their impact on health is only beginning to be studied. Ultrafines aren’t specifically regulated by any state or federal air quality standards.


Such particles are found in both vehicle and plane emissions. In fact, the UW researchers observed a higher concentration of ultrafines by roadways than by the airport.

But for the first time, researchers found a crucial difference in the type of ultrafines emitted by cars and trucks versus jet planes.

A higher proportion of the ultrafine particles (UFPs) in jet emissions are so small they can penetrate the central nervous system when inhaled, the report said.

Communities under flight paths, like SeaTac, Des Moines, Highline, Angle Lake, Beacon Hill and Rainier Valley, are exposed to those “ultra-ultrafines” when planes take off and land, researchers found.

The UW study adds to a growing international body of research on the particles, including some preliminary reports showing correlations between exposure to ultrafines and higher incidences of some kinds of cancer, as well as lung diseases that cause trouble breathing and deep, throaty coughs.

“Strong and consistent evidence from animal studies indicates that long-term exposure to UFPs is related to negative effects on the brain, nervous and respiratory system,” the state Department of Health concluded in a separate review of research on ultrafine particles released this month, funded by the Port of Seattle.


The department emphasized that more research is necessary to fully understand the health impacts of the particles on humans.

In other words, it’s far too early to say whether Palosaari’s cough has anything to do with ultrafines, said Dr. Elena Austin, one of the researchers on the UW study and an assistant professor at the school’s department of environmental and occupational health sciences.

It’s difficult to hear those stories, because it’s impacting those people’s health,” Austin said. “But I really don’t have an answer to even speak on a community level whether those illnesses are related to the aircraft emissions. It’s even harder to speak to an individual case.”

The UW study sampled particulate levels 10 miles north and south of Sea-Tac, near I-5 and at a control site for a year, finding the concentration of ultrafines by the airport was higher than at the Sand Point control site. Researchers weren’t able to say definitively how much higher because they sampled at different times of the year.

Those findings align with previous research at airports in Los Angeles, Atlanta, New York, Boston and Amsterdam that observed higher levels of ultrafine particles near airports.

But the study also found the concentration of ultrafine particles was consistently higher near I-5 than near Sea-Tac.


It’s those tinier airport particles, though, that make health researchers more worried.

Generally, Austin said, ultrafine particles tend to agglomerate as they travel through the air — they stick together and become larger particles, which aren’t able to pass from the airways into the bloodstream. That’s typically what happens near busy roads.

But the super-small particles emitted by airplanes are forced directly downward by air currents and wing vortexes so rapidly that they haven’t agglomerated by the time they reach the ground, her team found.

The concern is that these very small particles may react differently within the body,” Austin said. “They may cross tissue barriers that larger particles can’t cross.”

There’s another reason for extra concern about ultra-ultrafine particles from plane emissions, the study said. People tend to spend a relatively small part of their day on the road — but people who live near airports are potentially exposed to the pollutants throughout the day and night.

“In terms of their ultrafine exposure, it’s like people under that flight path are standing in the roadway,” said Dr. Joel Kaufman, a University of Washington epidemiologist unaffiliated with the airport study.


Last year, the Environmental Protection Agency said exploring the link between ultrafines and brain health was a priority research area.

Some researchers are beginning to suspect illnesses previously associated with larger particle pollution may actually be caused by ultrafines, but knowledge gaps about who’s exposed to ultrafines and at what level mean it’s impossible to come to any conclusions yet, Kaufman said. 

Kaufman is measuring ultrafine exposure in vehicles. And a colleague, Dr. Lianne Sheppard, is mapping ultrafine levels around Puget Sound for a long-term health outcomes study.

Researchers are also working with the City of Seattle to study ultrafine emissions and noise pollution from jet planes around Beacon Hill. They expect to release results early next year.

And in the future, scientists hope to be able to say what, exactly, the ultrafines in jet emissions are composed of. In this phase of the study, researchers didn’t have the equipment necessary to determine the chemical composition of the particles, Austin said.

In a statement, a Port spokesperson said the agency welcomes more research on airplane emissions and the feasibility of jet biofuels, which may reduce ultrafine particulate emissions.


As more data on ultrafine particles is collected, health researchers will be better able to conduct longer-term studies on the effects of exposure to ultrafines.

State Rep. Tina Orwall and Sen. Karen Keiser, representing communities around the airport, led the charge in Olympia on ultrafines research. They also secured funding for King County’s public health agency to study the airport’s health impact on surrounding communities.

The legislators and some at the Port say they’re interested in exploring ways to mitigate risk from exposure to ultrafines, even before there’s definitive evidence of the particles’ impact.

“As the data comes rolling in that the particles are there, the particles are bad, neither of which I need to be convinced of, the question for me becomes what are we going to do about it?” said Port of Seattle Commissioner Fred Felleman, the Commission’s incoming representative to the UW ultrafine research group’s advisory committee. 

One option under discussion is to install top-tier air filtration systems in schools around the airport.

The state Department of Health found that young people and the elderly are particularly vulnerable to emissions. But because researchers still don’t know how the particles come indoors, it’s unclear how much filtration would need to be installed to trap ultrafines, the UW study said.


Several times a day, Palosaari checks air quality readings on a meter in his backyard, and another portable meter he carries with him, transmitting the readings to a citizen research group monitoring airport pollution.

“You can never be totally certain that the disease is caused by airplane emissions,” Palosaari said. “But most people down here don’t need another study to prove to them there are health issues.”

A year ago, Palosaari was diagnosed with a brain aneurysm.

He said he understands there’s not enough evidence to say he’s been sickened by the plane emissions.

Regardless, he said he plans to move away from the airport. Part of the reason he monitors pollution so closely, he said, is because he’s “chasing air,” looking for somewhere to live without ultrafines.

“But there’s a lot of people who want to leave who can’t,” he said.