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1 This section provides a summary of the basic findings presented for a broad readership. Technical information is provided in the body of the report. To support airport operators, the purpose of this study was to evaluate the existing body of knowledge on airport air quality and public health to help better understand and respond to concerns over airport-related air quality health concerns. The work was accomplished through a review of past studies and a critical synthesis where conclusions were drawn from a preponderance of the evidence. This involved summarizing, corroborating, and refuting findings from the existing literature to extract general conclusions applicable to most airports. Since it is difficult to generalize to all airports, the conclusions were qualified to indicate that findings at specific airports may differ. To assist airport novice users, this report provides primer-type information in Chapters 2 through 4. These sections provide background information necessary to understand the conclusions drawn from the synthesis. In addition, Appendix B, Frequently Asked Questions (FAQs), provides direct answers to popular questionsâthose that are likely to be asked by novices. Chapter 5 presents the synthesis work shaped in the form of two basic questions: (1) What pollutants are of most concern at an airport? (2) What are the airportâs contributions to local air quality and health impacts? The key findings for airports are as follows: â¢ Factors that affect airport contributions to local air quality and public healthâIn addition to pollutant type, there are many factors that can affect airport contributions to local air quality and public health. These include pollutant emissions (largely affected by source characteristics and operations), pollutant toxicity, and exposure. In addition, a personâs background and condition also can play a significant role in affecting his/her health. Factors such as age, gender, pre-existing disease status, and co-exposures to other risk factors can all affect susceptibility to air pollutants. See Section 4.2 and the FAQs. â¢ Ability to state conclusions for specific airportsâSince all airports are different, it is very difficult to make general statements about airport air quality contributions and health impacts. Airport contributions to air quality can depend on many different fac- tors including, but not limited to, airport source types (e.g., aircraft fleet mixes), source operations, airport layout and location, surrounding geography, and meteorology. See Sections 3.1â3.5. â¢ Pollutant(s) that pose the biggest health risk at airportsâAirport risk assessment studies have shown that fine particulate matter (PM2.5) dominates the overall health risks posed by airport emissions. The risk for fine particles is orders of magnitude higher than that for the closest hazardous air pollutant (HAP), formaldehyde, although the ability to quantify the non-cancer health effects of HAPs is limited. PM2.5 levels have been found to vary sig- nificantly at different airports. Although PM10 is a health concern, the fact that much of the coarser portion is filtered out by the upper respiratory tract in human beings makes it less of a concern than are the finer particles. See Chapter 4 and Section 5.1. Summary of Findings
2 Understanding Airport Air Quality and Public Health Studies Related to Airports â¢ Secondary PM (PM not directly emitted from a source but formed in the atmosphere) at airportsâStudies indicate that secondary PM may form at significant distances downstream from an airport (many miles) adding to health impacts, and thus, requiring large-scale (e.g., regional) modeling to determine overall PM health impacts. In addition, the impacts of different PM components including black carbon, nitrates, and sulfates need to be taken into account as well as PM size distributions. See Chapter 4 and Section 5.2. â¢ Airport contributions of ultrafine PM (PM sized below 0.1 Âµm diameter)âIn addition to the suspected health concerns of ultrafine PM from airport sources (along the lines of the current understanding of PM2.5), measurement studies have shown that ultrafine concentrations tend to be highly elevated near an airport (near runways) with persistence above background levels at distances of 600 m downwind of an airport. As such, ultrafine PM generated by airports is suspected of having a broader impact than that generated by roadway vehicles. See Chapter 4 and Section 5.2. â¢ Consistency of airport contributions of HAPsâConcentrations of HAPs at airports seem to vary without clear, consistent levels of contributions. While some studies sug- gest that HAP concentrations near airports may be similar to background levels, there appears to be enough evidence suggesting otherwiseâkeeping in mind there are notice- able uncertainties with measured concentration levels. See Section 5.2. â¢ Airport contribution levels of most criteria gasesâAirport studies appear to indicate that most criteria gases (e.g., CO, NO2, and SO2) generated from airports generally tend to result in similar concentrations to background (or urban) levels in surrounding com- munities, although with appreciable contributions closer to the emission sources and variable conclusions depending on background levels. Although health effects of criteria gases are well defined, quantitative health risk assessments for these gases are relatively limited in comparison to ozone and PM. See Chapter 4 and Section 5.2. â¢ Airport contributions to ozoneâBecause of the nature of ozone chemistry, ozone levels around airports tend to be lower than background levels (i.e., airports tend to be a sink for ozone). Although ozone levels in the vicinity of an airport may be depressed, airports can contribute to the formation of ozone on a larger regional level, thus resulting in increased health impacts. See Section 5.2. â¢ Lead as a concern at airportsâLead is a health concern at general aviation (GA) airports and will continue to be an issue as long as AvGas is used. Current studies indicate that lead emissions can noticeably persist at distances close to 1,000 meters downwind of an airport. As such, studies indicate that lead contributions near GA airports may not be negligible. See Section 5.2. â¢ Airport air quality and public health researchâThe state of airport air quality and health research is currently not mature enough to allow definitive conclusions in most cases. As such, all conclusions should be considered snapshots in time since future research may provide further details. However, the current research efforts appear to be aligned with the prioritization of pollutant health risks. Based on the relative number of studies and the recent focus, available resources appear to be correctly being applied to PM and HAPs research, with consideration of ozone for regional-scale analyses. See Sections 5.1â5.2 and Appendix A at the back of the report. â¢ Correlating airport contributions to local air qualityâRegarding airport contributions to local air quality, studies have shown that airport emissions and resulting concentration contributions can be well correlated to airport operations (e.g., aircraft usage) as part of source identification and apportionment work. The more pertinent issue is in quantifying the contributions. The current research efforts appear to be aligned with the need for further measurements and understanding of health impacts. See Sections 5.1â5.2.