Communities around Sea-Tac Airport exposed to a unique mix of air pollution associated with aircraft

Communities underneath and downwind of jets landing at Seattle-Tacoma International Airport are exposed to a type of ultrafine particle pollution that is distinctly associated with aircraft, according to a new University of Washington study, the first to identify the unique signature of aircraft emissions in the state of Washington.

The finding comes from the two-year Mobile ObserVations of Ultrafine Particles or “MOV-UP” study funded by the Washington State Legislature to examine the air-quality impacts of aircraft traffic on communities located within 10 miles of Sea-Tac Airport.

Researchers at the UW Department of Environmental & Occupational Health Sciences and the Department of Civil & Environmental Engineering collected air samples at numerous locations around Sea-Tac Airport over the course of a year between 2018 and 2019.

The research team then developed a new method to distinguish between pollution from jet traffic and pollution from other sources such as roadway traffic. Ultrafine pollution particles are emitted from both sources, but the research team found key differences in the particle size and mixture of particles they emit.

The researchers then mapped each type of emission mixture to show its specific geographic footprint around the airport.

Read the full Mobile ObserVations of Ultrafine Particles or “MOV-UP” report

“We found that communities under the flight paths near the airport are exposed to higher proportions of smaller-sized, ‘ultra-ultrafine’ pollution particles and over a larger area compared to pollution particles associated with roadways,” said Edmund Seto, co-principal investigator and associate professor of environmental and occupational health sciences in the UW School of Public Health.

Ultrafine particles are less than 0.1 micron in diameter — 700 times thinner than the width of a single human hair. The research team coined the term “ultra-ultrafine” particles to refer to the proportion of smaller ultrafine particles between 0.01 to 0.02 microns in diameter.

Although this study did not consider the health effects of exposure to roadway or aircraft-related pollution, previous studies suggest smaller pollution particles are more likely to be inhaled and to penetrate the body than larger particles.

Other studies have linked exposure to ultrafine particles to breast cancer, heart disease, prostate cancer and a variety of lung conditions. The Washington State Department of Health is currently preparing a comprehensive literature review of the potential health effects associated with ultrafine particles.

The discovery of the unique signature of aircraft pollution opens up opportunities for follow-up studies, said Michael Yost, professor and chair of the Department of Environmental & Occupational Health Sciences.

“We can now study the specific health effects of aircraft-related pollution, how different neighborhoods may be affected by it and specific interventions that could reduce human exposure to these pollutants,” said Yost, who is also a co-investigator on the study. “We hope to work with state and local policymakers as well as affected communities to pursue these questions.”

The team gathered air samples from fixed locations, including a former elementary school south of the airport and SeaTac Community Center north of the airport. Researchers also collected air samples through mobile monitors mounted on hybrid vehicles that were driven on 11 routes north and south of the airport in time periods that covered all four seasons of the year.

The researchers used data from the Federal Aviation Administration and other sources to track the number and direction of flights, their altitudes and the wind speed and direction, temperature and relative humidity at the airport.

Their analysis showed that roadway air pollution particles consist of relatively larger particle sizes and higher black carbon concentrations. These particles tend to disperse over relatively short distances downwind of major roadways such as Interstate 5 and SR 99, affecting a narrow swath of near-roadway residences and buildings.

In contrast, emissions associated with aircraft consist of the relatively smaller ultra-ultrafine particle sizes and lower black carbon concentrations. Areas exposed to higher levels of aircraft-related particles tend to be larger, meaning more people are potentially affected.

The research team coordinated closely with local governments, community groups and state and federal agencies throughout the two-year project, soliciting feedback on the study design, analysis and next steps.

Sea-Tac Airport is the eighth busiest U.S. airport. In 2018, the airport served nearly 50 million passengers and saw 438,391 takeoffs and landings.

Co-authors include Elena Austin, Jianbang Xiang and Jeffry Shirai of UW Department of Environmental & Occupational Health Sciences; Tim Gould and Sukyong Yun from UW Department of Civil & Environmental Engineering; and co-senior author Timothy Larson, a professor in both departments. This research was funded by the Washington State Legislature.

This release was written by Jolayne Houtz, director of communications for the UW Department of Environmental & Occupational Health Sciences

Statement from the Port of Seattle:

“We are pleased to see the UW MOV-UP Study completed and turned into the Legislature. The Port strongly supports this effort and helped fund this study which we see as critical to advancing the science needed to understand and reduce fine particulate emissions. Our Commission remains committed to reducing the emissions associated with using fossil fuels, and one way to reduce emissions is through the use of lower-carbon transportation fuels. Many of these fuels including renewable diesel and sustainable aviation fuel reduce ultra-fine particulate in addition to greenhouse gases, the pollution that causes global warming. For this reason, we continue to urge the Washington State Legislature to move quickly towards statewide progressive carbon policy that encourages the adoption of low-carbon transportation fuels. That kind of policy framework could generate real progress on the full-scale implementation of sustainable fuels at the state’s airports and seaports.”

Statement from the Washington State Department of Health:

“Our comprehensive literature review of the potential health effects of ultrafine particle pollution is being completed alongside the UW study. Together, these studies will provide state policymakers and communities with evidence about where and how this type of traffic-related pollution affects people and inform future steps to protect public health,” said Julie Fox, environmental epidemiologist, Washington State Department of Health.