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92 A P P E N D I X B Question: What types of health impacts can airport emissions cause? Answer: In general, both gaseous and particulate matter emissions from airports can cause harm to the human respiratory and cardiovascular systems. Effects can range from minor exacerbations of existing conditions to increased risk of hospitalization and premature death. Exposure to certain pollutants also can cause skin irritations and other physical effects, especially in sensitive individuals. Question: What are the main air pollutants of concern? Answer: As with other transportation sources, airport sources can emit all of the criteria pollutants (CO, NOx, VOC, SOx, Pb, PM10, and PM2.5) including the precursors that form O3 and other secondary pollutants including various PM species. Also, HAPs such as formaldehyde, acrolein, acetaldehyde, etc., can be emitted from various sources. However, the main pollutant from a local health risk potential is PM2.5, with important effects of ozone at longer range and increasing concern about ultrafine particles in the near field. Formaldehyde tends to have the most cancer risk among HAPs species. Important non-cancer effects of HAPs may exist but are challenging to quantify. Question: What are the differences between ambient standards, exposure thresholds, and cancer risk indicators? Answer: Ambient standards, such as the National Ambient Air Quality Standards (NAAQS) are outdoor air pollutant concentration levels maintained by the EPA to monitor air pollution levels in different regions of the country. These are generally intended to be adequately protective of sensitive subpopulations. Exposure thresholds for air pollutants generally refer to concentra- tion levels where below those levels, human beings are not considered to be at health risk. More specifically, exposure threshold levels and limits have been used by various organizations such as OSHA, NIOSH, and ACGIH to define and recommend levels/limits for workplaces to protect workers from harmful exposure. Cancer risk factors for air pollution are factors that may directly or indirectly cause or support the formation of cancer due to pollutant exposure. These factors may include a personâs age, sex, family cancer history, etc., and can serve to help determine the probability (the risk) of developing cancer. Question: Besides pollutant type, what other factors affect public health? Answer: Besides pollutant type, emission rates, toxicity, individual and population exposure, and vulnerability attributes are important factors that can affect public health. Indeed, all of these fac- tors are important components in properly assessing the health risk of each pollutant. Individual exposure encompasses the pathway from the source to human activity locations (e.g., homes, workplaces, etc.) as well as how long a person is exposed to the pollutants. Population exposure integrates across individual exposures to provide measures relevant to the entire population. In addition, a personâs background and condition also can play a significant role in affecting his/her Frequently Asked Questions
Frequently Asked Questions 93 health. Factors such as age, gender, pre-existing disease status, and co-exposures to other risk factors can all affect susceptibility to air pollutants. Question: What are the significant sources of pollutants at an airport? Answer: The significant sources of pollutants at an airport generally arise from the combustion of fuelsâfor example from an aircraft engine, ground support equipment (GSE), etc. The highest contributing emissions sources tend to be aircraft, GSE, and ground access vehicles (GAVs). Air- craft engines are significant sources of emissions in all phases of their operation, such as approach, landing, idling/taxiing, takeoff, and climb out, but the significance for each pollutant depends on the mode (or phase) of aircraft operation. Question: What emissions mitigation measures have airports implemented? Answer: Airports have implemented mitigation measures to address the key pollutants and the most significant sources. To mitigate aircraft emissions, airports have implemented measures to reduce taxiing and runway holding times, electrified gates to provide preconditioned air and power, etc. The use of electric GSE and alternative fuels (e.g., CNG) also has helped reduce emis- sions in gate areas. For mitigating road traffic emissions, airports are dependent on influencing individuals and other organizations to change their behavior or practices. Many airports have promoted public transport use, especially where this involves low-emitting vehicles, and have invested in consolidating certain activities, such as rental car facilities, into one location. Question: What are the differences between criteria pollutants and HAPs? Answer: In the 1970 Clean Air Act Amendments, the EPA established criteria, or ambient air concentrations, that define the maximum acceptable level for each of the six criteria pollutants that affect public health and the environment. The concentrations are referred to as the National Ambient Air Quality Standards (NAAQS), and the criteria pollutants include carbon monoxide (CO), nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone (O3), lead (Pb), and particulate matter (PM) in two forms, inhalable (coarse) particulate matter (PM10), and fine particulate matter (PM2.5), which are very small particles with a diameter 2.5 micrometers or less. The U.S. Environmental Protection Agency (EPA) identified 187 hazardous air pollutants (HAPs) that cause other more serious health effects, and are known to, or suspected of, causing cancer in humans. Hazardous air pollutants also are referred to as toxic air pollutants (or air toxics), and the terms can be used interchangeably. Most HAPs are emitted from anthropogenic (manmade) sources such as exhaust from aircraft engines powered by fossil fuels and from sta- tionary sources such as boilers and power plants. Examples of HAPs (and their sources) include formaldehyde (aircraft), benzene (gasoline), perchloroethylene (dry cleaning), and methylene chloride (paint stripper). Question: What are the differences between primary and secondary pollutants? Answer: Primary air pollutants are emitted directly from a source such as aircraft and GSE engines containing pollutants such as CO, NOx, SOx, PM2.5, HAPs, etc. However, some pollutants are not emitted directly and form only as a result of complex chemical reactions in the atmosphere involving precursor pollutants. These formed pollutants are referred to as secondary pollutants. For example, ozone is generally not emitted directly from a source but is formed through the photochemical reaction of naturally occurring oxygen in the atmosphere, together with emissions of nitrogen oxides (NOx) and volatile organic compounds (VOCs) in the presence of sunlight. Fine particulate matter (PM2.5), a pollutant that has been associated with increased mortality and morbidity in areas where concentrations of the pollutant are elevated, also has significant con- tributions from secondary formation. Although PM2.5 can be emitted directly, the pollutant also can be formed through chemical reactions involving NOx, SO2, and VOCs, leading to formation of sulfate, nitrate, and organic aerosol particles.
94 Understanding Airport Air Quality and Public Health Studies Related to Airports Primary and secondary pollutants are not to be confused with the primary and secondary standards established for the National Ambient Air Quality Standards (NAAQS). The NAAQS establish the maximum allowable concentrations of the criteria air pollutants for the protection of public health (primary standards) and protection of the environment (secondary standards). Question: What health-related airport air quality studies have been conducted? Answer: Although the overall literature on this topic is relatively small compared to studies that have been conducted for roadway sources and other industries, the breadth and depth of research in this area has been growing. Sections 5.1 and 5.2 provide reviews of selected airport air quality and health studies. Appendix A, Literature Review Summary and References, provides a larger list of studies reviewed under this project. The studies range from specific airport health research to more general airport air quality and health studies for other industries.
Abbreviations and acronyms used without definitions in TRB publications: A4A Airlines for America AAAE American Association of Airport Executives AASHO American Association of State Highway Officials AASHTO American Association of State Highway and Transportation Officials ACIâNA Airports Council InternationalâNorth America ACRP Airport Cooperative Research Program ADA Americans with Disabilities Act APTA American Public Transportation Association ASCE American Society of Civil Engineers ASME American Society of Mechanical Engineers ASTM American Society for Testing and Materials ATA American Trucking Associations CTAA Community Transportation Association of America CTBSSP Commercial Truck and Bus Safety Synthesis Program DHS Department of Homeland Security DOE Department of Energy EPA Environmental Protection Agency FAA Federal Aviation Administration FHWA Federal Highway Administration FMCSA Federal Motor Carrier Safety Administration FRA Federal Railroad Administration FTA Federal Transit Administration HMCRP Hazardous Materials Cooperative Research Program IEEE Institute of Electrical and Electronics Engineers ISTEA Intermodal Surface Transportation Efficiency Act of 1991 ITE Institute of Transportation Engineers MAP-21 Moving Ahead for Progress in the 21st Century Act (2012) NASA National Aeronautics and Space Administration NASAO National Association of State Aviation Officials NCFRP National Cooperative Freight Research Program NCHRP National Cooperative Highway Research Program NHTSA National Highway Traffic Safety Administration NTSB National Transportation Safety Board PHMSA Pipeline and Hazardous Materials Safety Administration RITA Research and Innovative Technology Administration SAE Society of Automotive Engineers SAFETEA-LU Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (2005) TCRP Transit Cooperative Research Program TEA-21 Transportation Equity Act for the 21st Century (1998) TRB Transportation Research Board TSA Transportation Security Administration U.S.DOT United States Department of Transportation
TRA N SPO RTATIO N RESEA RCH BO A RD 500 Fifth Street, N W W ashington, D C 20001 A D D RESS SERV ICE REQ U ESTED ISBN 978-0-309-30864-9 9 7 8 0 3 0 9 3 0 8 6 4 9 9 0 0 0 0 N O N -PR O FIT O R G . U .S. PO STA G E PA ID C O LU M B IA , M D PER M IT N O . 88 U nderstanding A irport A ir Q uality and Public H ealth Studies Related to A irports A CRP Report 135 TRB
