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43 C H A P T E R 7 The following provides a summary of the existing knowledge gaps and recommended future research to help advance the understanding of airport air quality contributions and public health impacts. â¢ In general, more health-related research is necessary to gain a better understanding of airport air quality contributions and health impacts. This includes more airport air quality monitoring programs and additional health risk assessments that should involve both airport and system levels. Understanding the health risks attributable to an individual airport requires atmospheric modeling and health risk assessment specific to the individual airport, and these efforts should be prioritized to provide insight to individual airport operators. â¢ Since, from recent risk assessments, PM seems to pose the greatest risk to human health, more specific characterization studies of fine particles (PM2.5), ultrafines, PM components, and size distributions are necessary. Health effects and risks of ultrafines and PM components (e.g., nitrates, sulfates, etc.) are not well understood. More characterizations are necessary to determine what further differences may exist between primary PM directly emitted from air- craft versus secondary PM formed in the atmosphere, as well as emitted from other sources (e.g., roadway vehicles). â¢ Although PM and HAPs are the priority, gaseous criteria pollutants need further research to better understand their health risks (i.e., in addition to current understanding of their health effects). â¢ More research on the overall risks posed by lead emissions from GA aircraft is necessary. This should include more measurements as well. â¢ Modeling uncertainties need to be better understood so that health risk assessments can be made more reliable with clearer (or smaller) error bands. This includes uncertainties in emissions inventories, atmospheric dispersion models, and in the underlying health evidence. â¢ With the importance of PM2.5 health impacts, the PM emissions data, as well as emissions of particle precursors (VOCs, NOx, SO2), need to be as accurate as possible. More mass and size- based PM measurements of aircraft engines should be conducted to develop a more accurate set of emission factors (emissions indices). â¢ Research needs to be conducted on interactions with the following other health impacts: â Multi-pollutant epidemiological investigations should be conducted to assess potential synergies and interactions of different pollutants on health effects. â Similarly, risks associated with air pollution and noise combined should be assessed to determine what interactions may exist. â¢ Although some source apportionment methods such as the Chemical Mass Balance (CMB) have been used, some guidance or clarification of the methods would be helpful. â¢ In addition to risks placed on the public, more assessments should be conducted on airport workers (e.g., GSE operators) since they are much closer to the sources. Also, more studies should be conducted (with measurements) on the risks to passengers. Recommendations for Future Research
44 Understanding Airport Air Quality and Public Health Studies Related to Airports â¢ Further research is needed to determine aircraft power setting (and operations) influences on emitted PM characteristics, including size and chemical characteristics. â¢ Research should be conducted to improve aircraft taxiing/idle and engine start emissions modeling. These transient conditions tend to have different emissions characteristics than steady-state conditions. â¢ In addition to dispersion modeling, local atmospheric chemistry modeling should be further investigated/improved since AERMOD generally does not have chemistry modeling capabilities (beyond the use of decay rates and simplified NOx chemistry). Although CMAQ has a large set of chemistry mechanisms, it uses larger grid sizes that make finer spatial resolution assessments difficult. Nested modeling capabilities can be applied, but require greater resources, and there remains the need to use ambient monitoring to validate dispersion modeling outputs. â¢ Rather than using the typical 1-hour or coarser concentrations from models like AERMOD, time-varying models should be investigated to provide more robust modeling environments to conduct health risk assessments.