The impact of aviation activities on ambient particle number concentration and incident hypertension
Kim, Chloe Seyoung
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Aviation industry has played an essential role in modern society by providing social and economic benefits, but with inevitable environmental and public health implications. Communities living near airports are potentially affected by increased exposures to aviation-related emissions as well as noise. Better characterization of the impacts of aircraft emissions and noise is of great public health concern, especially for those living in communities near airports. The goal of my dissertation was to investigate the contribution of arrival aircraft to ambient ultrafine particulate matter (UFP) concentration as well as to examine the impact of aircraft noise on hypertension. Various aviation-related air pollutants have been studied, including UFP, due to the high emission rates from aircraft and potential adverse health effects. Multiple studies have concluded that aircraft arrivals contribute significantly to ambient UFP concentration over a broad geographic area, but few studies have had the necessary monitoring infrastructure to formally evaluate the magnitude and spatial extent of impact. Because of its small size and negligible mass, UFP has significant spatial and temporal variability, which warrants further investigation in order to better understand its dispersion patterns and impact in communities near airports. In our study, we collected UFP concentration data, measured as particle number concentration (PNC), at multiple locations near a major arrival flight path into Boston Logan International Airport, gathering concurrent flight activity and meteorological data for the purpose of source attribution. Two study aims were developed in order to better understand the arrival aircraft contribution to ambient PNC: 1) to investigate the spatiotemporal pattern of PNC concentrations across multiple study sites that are at varying distances from arrival aircraft flight paths, and 2) to quantify the PNC contribution from individual aircraft while explicitly accounting for meteorology, considering the implications of utilizing different averaging times and distributional characterizations (e.g., mean, 95th percentile). Results of the first aim of this study indicated that being downwind of the airport as well as the arrival flight path under higher wind speed was associated with elevated PNC. In addition, during hours of high flight activity, the aircraft contribution to ambient PNC was detectable even at a site 17 km away from the airport. The second aim of the study found a significant contribution of arrival aircraft to ambient PNC even when controlling for other important predictors in multivariable regression models. Our models also revealed that using the 95th percentile PNC within an hour led to larger estimates of arrival aircraft contributions than using the mean PNC, corresponding to strong and intermittent signal from aviation. Similar to UFP, aircraft noise also displays strong spatiotemporal variability and has been shown to be associated with an array of adverse health outcomes including sleep disturbance and increased blood pressure in exposed communities. Though there is accumulating evidence of the association between aircraft noise and hypertension, existing studies are not without limitations. In our study, we developed long-term time-varying aircraft noise estimates for 90 airports in the U.S. using a single noise model and assigned noise estimates based on geocoded addresses of participants in Nurses’ Health Studies (NHS and NHS II), two existing large prospective cohorts of women. The aim of this study was to examine the association between aircraft noise and incident hypertension in female nurses utilizing high temporal and spatial resolution aircraft noise exposure estimates in order to reduce potential exposure misclassification while accounting for temporality. Our study results showed an increased risk for incident hypertension associated with increased aircraft noise in both cohorts controlling for potential confounders. Our study also confirmed the impact of aircraft noise on hypertension apart from that of air pollution. In summary, we found that aircraft activity can contribute significantly to ambient PNC. We developed a spatiotemporal model of aircraft noise and found that it is significantly associated with increased risk for hypertension in a large prospective cohort study, independent of the effects of air pollution on hypertension. Together, our work reinforces the importance of quantifying the environmental and public health impacts of aviation activities and provide future directions for research.