Abstract:
Background: JP-8, Jet A-1, and Jet A are kerosene-based aviation fuels. Jet fuel combustion produces complex pollutant mixtures including VOCs, CO2, CO, NOx, SOx, PAHs and PM. Particles are characterized by size, with ultrafine particles (UFPs -- those particles < 100 nm in diameter) typically quantified by particle number concentration. Previous studies have reported higher concentrations of small UFPs from aircraft combustion emissions, reported as concentrations in the 5 to 40 nm in diameter range. The size distribution and concentration are dependent on the aircraft type, engine, airport, and weather conditions, suggesting that health outcomes may vary by exposure scenario. Exposures to UFPs have been associated with decreased lung function and increased airway inflammation in those with asthma, as well as oxidative stress in those who are healthy. The goal of this study was to characterize outdoor particle exposures under the flight path near Sea-Tac International Airport in SeaTac, Washington, and to demonstrate feasibility of assessing differences in short-term cardiorespiratory outcomes using crossover study design with controlled exposures and a repeated health measures design.
Methods: All data for the study were collected at the SeaTac Community Center (Center) located in SeaTac, Washington. The Center is directly under the flight path of Sea-Tac International Airport, with the north end of the runways located approximately 1.5 km southwest of the site. Data collection occurred in two separate phases: Phase 1 was a preliminary exposure sampling day in October 2021 to test the study design and protocols. During this phase, a powered air purifying respirator (PAPR) was tested to ensure efficacy in removing ultrafine particles under the face shield. Phase 2, a randomized blinded crossover study of four adults, two healthy and two with well-controlled asthma, was conducted in May 2022. In the crossover study, participants walked a set path around the perimeter of the Center for 90 minutes, wearing a sham filter on one day (exposed), and a working filter (not exposed) on a different day. Repeated cardiorespiratory assessments were conducted on both days at baseline (before walk), and at resting periods 30, 60, and 90 minutes during the walk. Air monitoring instruments were used to measure NO2, BC, PM0.3 to PM10, and UFP concentrations. Noise measurements were also collected during the study. Health measurements included neuropsychological (Stroop test and Ecological Momentary Stress questionnaire), cardiological (blood pressure (BP), heart rate (HR) and heart rate variability (HRV), and respiratory (spirometry) data. Day-specific baseline-adjusted differences between exposed and non-exposed conditions were used to assess the health effects at the three time points.
Results: UFPs were observed at higher concentrations in the smaller size bins, with the highest counts measured for sizes 36.5 nm and below. The particles with the greatest counts were often found in the 11.5 and 20.5 nm size range, which is typically attributed to aircraft emissions. HR, HRV, FEV1, and FVC were observed to have the biggest effects with exposure for the asthmatic group. For HR and HRV, opposite effects were found with exposure for healthy versus asthmatic groups. The healthy group’s HRV increased while the asthmatic group decreased at the 90-minute time. The healthy and asthmatic groups had increased and decreased FEV1 and FVC at the same time points, with the asthmatic group exhibiting greater effects with exposure.
Conclusion: Smaller UFPs were shown to be in higher concentrations during takeoff and when landing was more frequent. Preliminary findings from the small crossover study illustrate potential differences in cardiorespiratory health effects with exposure between healthy and asthmatic with aircraft-related air pollution exposure. However, a larger study is needed to determine if these preliminary findings are robust.