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Understanding Airport Air Quality and Public Health Studies Related to Airports (2015)

Chapter: Chapter 5 - Current Understanding of Airport Air Quality Health Impacts

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Suggested Citation:"Chapter 5 - Current Understanding of Airport Air Quality Health Impacts." National Academies of Sciences, Engineering, and Medicine. 2015. Understanding Airport Air Quality and Public Health Studies Related to Airports. Washington, DC: The National Academies Press. doi: 10.17226/22119.
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Suggested Citation:"Chapter 5 - Current Understanding of Airport Air Quality Health Impacts." National Academies of Sciences, Engineering, and Medicine. 2015. Understanding Airport Air Quality and Public Health Studies Related to Airports. Washington, DC: The National Academies Press. doi: 10.17226/22119.
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Suggested Citation:"Chapter 5 - Current Understanding of Airport Air Quality Health Impacts." National Academies of Sciences, Engineering, and Medicine. 2015. Understanding Airport Air Quality and Public Health Studies Related to Airports. Washington, DC: The National Academies Press. doi: 10.17226/22119.
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Suggested Citation:"Chapter 5 - Current Understanding of Airport Air Quality Health Impacts." National Academies of Sciences, Engineering, and Medicine. 2015. Understanding Airport Air Quality and Public Health Studies Related to Airports. Washington, DC: The National Academies Press. doi: 10.17226/22119.
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Suggested Citation:"Chapter 5 - Current Understanding of Airport Air Quality Health Impacts." National Academies of Sciences, Engineering, and Medicine. 2015. Understanding Airport Air Quality and Public Health Studies Related to Airports. Washington, DC: The National Academies Press. doi: 10.17226/22119.
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Suggested Citation:"Chapter 5 - Current Understanding of Airport Air Quality Health Impacts." National Academies of Sciences, Engineering, and Medicine. 2015. Understanding Airport Air Quality and Public Health Studies Related to Airports. Washington, DC: The National Academies Press. doi: 10.17226/22119.
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Suggested Citation:"Chapter 5 - Current Understanding of Airport Air Quality Health Impacts." National Academies of Sciences, Engineering, and Medicine. 2015. Understanding Airport Air Quality and Public Health Studies Related to Airports. Washington, DC: The National Academies Press. doi: 10.17226/22119.
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Suggested Citation:"Chapter 5 - Current Understanding of Airport Air Quality Health Impacts." National Academies of Sciences, Engineering, and Medicine. 2015. Understanding Airport Air Quality and Public Health Studies Related to Airports. Washington, DC: The National Academies Press. doi: 10.17226/22119.
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Suggested Citation:"Chapter 5 - Current Understanding of Airport Air Quality Health Impacts." National Academies of Sciences, Engineering, and Medicine. 2015. Understanding Airport Air Quality and Public Health Studies Related to Airports. Washington, DC: The National Academies Press. doi: 10.17226/22119.
×
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Suggested Citation:"Chapter 5 - Current Understanding of Airport Air Quality Health Impacts." National Academies of Sciences, Engineering, and Medicine. 2015. Understanding Airport Air Quality and Public Health Studies Related to Airports. Washington, DC: The National Academies Press. doi: 10.17226/22119.
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Suggested Citation:"Chapter 5 - Current Understanding of Airport Air Quality Health Impacts." National Academies of Sciences, Engineering, and Medicine. 2015. Understanding Airport Air Quality and Public Health Studies Related to Airports. Washington, DC: The National Academies Press. doi: 10.17226/22119.
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Suggested Citation:"Chapter 5 - Current Understanding of Airport Air Quality Health Impacts." National Academies of Sciences, Engineering, and Medicine. 2015. Understanding Airport Air Quality and Public Health Studies Related to Airports. Washington, DC: The National Academies Press. doi: 10.17226/22119.
×
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Suggested Citation:"Chapter 5 - Current Understanding of Airport Air Quality Health Impacts." National Academies of Sciences, Engineering, and Medicine. 2015. Understanding Airport Air Quality and Public Health Studies Related to Airports. Washington, DC: The National Academies Press. doi: 10.17226/22119.
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28 C H A P T E R 5 This chapter provides the current state of research related to potential health impacts from air- port pollutant emissions. It has been organized to respond to the following basic, key questions: • What pollutants are of most concern at an airport? • What are the airport contributions to local air quality and health impacts? The answers to these questions were obtained through a preponderance of the existing research studies conducted in this area. The latter question is a combination of airport contributions to ambient pollutant concentration levels as well as potential health impacts (risks). Because these issues typically accompany each other, they were integrated into one overall question. With on-going research in all of these areas, it should be noted that the answers are representative of a snapshot in time, and they may change with future research. Although there are some overlaps in the answers, they are kept to a minimum but are necessary to properly answer each question. Current Understanding of Airport Air Quality Health Impacts 5.1 What Pollutants Are of Most Concern at an Airport? 5.1.1 Evaluations At first glance, the answer to the question of which pollutants are of most concern may simply be based on what pollutants are emitted by the airport and their toxicities. But in order to answer this question, one must consider the risks associated with each pollutant. As previously explained, risk involves taking into account emissions and exposure in addition to toxicity. Just considering toxicity may cause undue attention to be paid to a pollutant that may be emitted in small quantities at an airport such that it may pose minimal risks to the public. In contrast, just focusing on pollutants with high emission rates overall (for the whole airport) may cause undue attention to pollutants with relatively low toxicity that may have little or no impact on the public. In addition, the exposure pathway needs to be considered. If an airport is located in a region To promote the understanding of airport health impacts, this section tackles two basic questions dealing with the pollutants of most concern (highest risk) and the airport contributions to local air quality and potential health impacts. The purpose of answering these questions is to better understand the current health implications of air pollutants generated by airports as a whole. The overall results and conclusions are not intended for scrutinizing individual airports because each airport presents unique characteristics.

Current Understanding of Airport Air Quality Health Impacts 29 where the geography and meteorological patterns are such that most of the emitted pollutants tend to move away from populated areas, the risks associated with that airport may be less than with an airport with lower levels of emissions but with dispersion and atmospheric chemistry conditions that are conducive to exposing larger portions of the public. As a result, it can be very difficult to determine risks in a general sense across all airports (or even a group of airports) since each has distinctly different characteristics (e.g., mixes of sources, airport layout, operations, etc.). Therefore, each airport needs to be assessed separately for each pollutant, and all of the aforementioned factors need to be taken into account. That said, researchers still attempt to define risks in a general sense to provide helpful infor- mation that may be used as a screening-type starting point to help the aviation community make better decisions regarding airport planning efforts and emissions mitigation measures. That is, the research results could help identify which pollutants to target for such efforts so airports could make efficient use of resources, and also serve as a basis for future research work. In developing ACRP Report 7—Aircraft and Airport-Related Hazardous Air Pollutants: Research Needs and Analysis (Wood et al. 2008), researchers focused on prioritizing HAP compounds. The prioritization was conducted based on combining emissions rates and toxicity, but without consideration of possible variability in the emissions-to-exposure relationship. Although both exposure pathway and the characteristics of the exposed groups were described as a necessary component in risk assessments, they were not included because they were outside the scope of the project. As such, the resulting prioritized list and research was intended to serve as an initial assessment to help identify information gaps. The study involved reviewing emissions inventories from several major airports (e.g., BOS, PHL, ORD) for emissions contributions from each of the airport sources (aircraft, GSE, GAV, etc.), and the development of risk-based concentrations (RBCs) to serve as measures of toxicity for each pollutant. The resulting prioritized list is provided in Table 5-1. Table 5-1 compares the prioritized list of pollutants developed from ACRP Report 7 to those from an FAA 2003 analysis (URS 2003) and the ORD 2005 airport modernization environmen- tal impact statement (EIS) (FAA 2005). The FAA-developed list was based just on emission rates while the ORD study used both emission rates and toxicity. The different results between the ACRP and ORD studies are largely attributed to different toxicity weighting schemes. These lists show similarities such as formaldehyde being included within the top three in all lists, but significant differences such as the fifth-place location of acrolein on the FAA list while it is first on the other two lists. A study conducted under the FAA’s Partnership for AiR Transportation Noise & Emissions Reduction (PARTNER) Program also involved the development of a prioritized list of pollutants Table 5-1. Prioritized list of pollutants from ACRP Report 7. Source: Wood et al. 2008

30 Understanding Airport Air Quality and Public Health Studies Related to Airports emitted from airport sources (Levy 2008). The study included assessments of emissions of criteria pollutants and HAPs but focused on fine particles (PM2.5), ozone, and a selected group of HAPs (formaldehyde, acetaldehyde, benzene, toluene, acrolein, etc.). This reduced pollutant focus was based on a screening analysis that determined that the excluded compounds pose significantly less risk. Also, for pollutants such as NO2, the literature was considered inadequate to develop the required concentration-response functions for the required risk assessments, and preliminary evidence indicated a greater criteria pollutant health impact from PM2.5 and ozone (EPA 2004 and 2005). The study included emissions from three airports: Chicago O’Hare International Airport (ORD), Hartsfield-Atlanta International Airport (ATL), and T.F. Green Airport (PVD). These airports were selected based on size, likely magnitude of impact, and location. Emissions inven- tories for each airport were prepared with the FAA’s EDMS/AEDT, and dispersion modeling was performed using AERMOD and CMAQ, the latter of which was used with different grid cell sizes. For the main comparison work, an intake fraction was defined as a “unitless measure charac- terizing the total population exposure to a compound per unit emissions of that compound or its precursor.” This metric was used to represent population-based exposures, which correspond directly with health risks for pollutants with linear concentration-response functions, and it allowed for rapid comparisons among pollutants and airports. The intake fraction also allowed for rapid estimation of health risks, as it was beyond the scope of this screening-level analysis to conduct more detailed health risk modeling. Tables 5-2 and 5-3 provide comparisons of the risks by pollutant for each airport studied. The risk values (deaths/year) indicate that fine particles (PM2.5) clearly dominate the overall risk and their impacts are magnitudes higher than the other pollutants. For example, the risks for ORD are as follows: • Total fine particles: 15 deaths/year, • Total HAPs (air toxics): 0.09 deaths/year, and • Highest ranking HAP (Formaldehyde): 0.043 deaths/year. These results are consistent with general EPA risk statistics that also show significantly higher risks posed by fine particles (see http://www.epa.gov/ttn/atw/nata1999/tables.html). Furthermore, the study was simplified (for comparison purposes) such that the HAPs risks are actually cancer risks with only a fraction of that corresponding to death. As such, the relative contribution of fine particles would be even higher in comparison. Non-cancer effects such as those from acrolein and various other pollutants were not considered as part of the prioritiza- tions, because the data available were not amenable to quantification, although the researchers noted that ambient acrolein in the grid cells surrounding the three airports exceeded its RfC, implying potential health effects. This would imply that other HAPs with respiratory effects also could contribute health effects following the non-cancer risk assessment approach used by EPA and others; this would potentially include acetaldehyde, formaldehyde, naphthalene, styrene, and toluene. The negative values for ozone risk in Table 5-3 are indicative of the nuances of ozone chemistry where increasing NOx emissions can reduce ozone concentrations over an area. As part of the study, the prioritized list of HAPs by risk was compared to rankings based on just emissions and emissions with toxicity (potency). As indicated in Table 5-4, formaldehyde is at the top of each list, but there are significant differences. For example, without taking into account toxicity or exposure, the emissions-based list shows acetaldehyde as second while the others have the pollutant in sixth place. This comparison helps to exemplify the need to include all aspects of risk so that the relative impacts of such pollutants are properly understood.

Current Understanding of Airport Air Quality Health Impacts 31 Source: Levy et al. 2008 Table 5-3. Population risk (deaths/year) for three airports using CMAQ (12- and 36-km grids). Source: Levy et al. 2008 Table 5-2. Population risk (deaths/year) for three airports using AERMOD (50-km radius).

32 Understanding Airport Air Quality and Public Health Studies Related to Airports The pollutants selected for this project represent those that have the greatest risks based on airport emission levels and toxicity. Another study conducted under the PARTNER Program (Project 15) used a combina- tion of CMAQ and the Environmental Benefits Mapping and Analysis Program (BenMAP) to study airport air quality impacts from 325 U.S. airports, focusing on the nonattainment areas (Ratliff et al. 2009). BenMAP uses health impact functions for criteria air pollutants to relate changes in air concentrations to a change in the incidence of a health endpoint. Only the impacts from PM and ozone were included in the study. Similar to the previous studies, the modeled results indicated that almost all of the health impacts were due to fine particles with about 160 cases of PM-related premature mortality per year. Health impacts such as chronic bronchitis, non-fatal heart attacks, respiratory and cardiovascular illness, also were associated with aircraft emissions. Source: Levy et al. 2008 Table 5-4. HAPs rankings based on different prioritization schemes. Although health concerns are associated with each of the criteria pollutants, the greatest risks (i.e., cancer and morbidity) seem to be posed by PM and HAPs. Specifically, fine PM (PM2.5) appears to pose the greatest risk to human health— magnitudes higher than HAP species. Formaldehyde was ranked as the HAP species having the greatest risk. Although ultrafines are inherently included as part of PM2.5, further research is necessary to better understand potential health impacts from ultrafines.

Current Understanding of Airport Air Quality Health Impacts 33 5.1.2 Summaries and Conclusions Studies such as these illustrate the need to conduct further research on more pollutants and other airports, but they indicate that, with regard to the potential for health impacts (risk), fine particulate matter appears to pose the greatest risk. As such, much of the current research in airport air quality has focused on fine particles. Among criteria air pollutants, ozone also can contribute significantly to public health impacts, although it would have a lesser impact in the near field and has been excluded from some previous analyses given methodological limitations. For HAPs, formaldehyde was ranked as having the highest risk followed by others such as 1,3-butadiene, styrene, naphtha- lene, benzene, acetaldehyde, etc. Although fine particles may pose much greater risk, it does not negate the need to further investigate other pollutants. In addition, although many previous analyses have focused on fine particulate matter mortality given its large contribution to monetized health impacts, additional health outcomes from PM2.5 and other pollutants merit inclusion. 5.2 What Are the Airport Contributions to Local Air Quality and Health Impacts? 5.2.1 Evaluations The health effects of each pollutant are summarized in Chapter 4. Although there are uncertain- ties associated with the toxicities, exposures, etc., the effects are well documented. Organizations such as the EPA and the World Health Organization (WHO) provide extensive information on pollutant health effects. • EPA Risk: http://www.epa.gov/oia/air/pollution.htm • WHO Risk: http://www.who.int/mediacentre/factsheets/fs313/en/ Although the overall airport emissions characteristics (mix of pollutants, chemical character- istics, sizes ranges for PM, etc.) may not be the same as other sources, the health effects of each pollutant are the same. That is, all other things being equal, a mass of a pollutant emitted from an airport will produce the same health effects as the same amount from other sources (or another airport)—if the pollutants are identical (no differences in characteristics). This section presents summaries of selected studies to illustrate the air pollutant concentration levels (and their variability) that can be found at different airports and implications for their contributions to local air quality. As such, most studies that have addressed the question of airport impacts on local air quality and health impacts have used data from measurements or modeling results to provide indications of exposure (either with emissions or ambient pollutant concentrations) and have linked these data with literature-based concentration-response functions within human health risk assess- ments. These encompass correlating aircraft activities (e.g., aircraft operations) with emissions, modeling how those emissions influence concentrations, and comparing airport concentration contributions to background levels. Since no two airports are the same, it is difficult to make general statements regarding airport contributions to local air quality because this depends on many factors including emissions strength (emission factors), airport layout, local meteorology, etc. Although further studies are needed, the available findings from the literature can be used to provide some general understandings of airport contributions. As such, each of the studies cited

34 Understanding Airport Air Quality and Public Health Studies Related to Airports in the references was reviewed, and the following abridged summaries of selected references provide an indication of the wide range of different types of studies and results available for consideration for further details: • ACRP Report 71: Guidance for Quantifying the Contribution of Airport Emissions to Local Air Quality (Kim et al. 2012). The goal of the project was to better understand the use of modeling and measurement capabilities to determine airport contributions to air quality. This included measurements of ambient concentrations for both criteria pollutants and HAPs. • The Impact of NOx, CO and VOC Emissions on the Air Quality of Zurich Airport (Schurmann 2007). Ambient measurements of criteria pollutants were performed to assess the impact of airport emissions on local air quality. • T.F. Green Airport Air Monitoring Study (RIDEM 2008). A monitoring study was conducted by the Rhode Island Department of Environmental Management (RIDEM) to assess air qual- ity levels and health risks to surrounding neighborhoods. Measurement sites were located around the airport with some near runways. The goal of the study was to characterize HAP concentrations in communities near the airport, assess contributions from different sources (e.g., aircraft, GSE, motor vehicles), verify modeling outputs, and develop a baseline that can be used to assess impacts of future airport changes. • Preliminary Study and Analysis of Toxic Air Pollutants from O’Hare International Airport and the Resulting Health Risks Created by These Toxic Emissions in Surrounding Residential Com- munities (ENVIRON 2000). The study used emissions data collected in 1999 to conduct a health risk assessment for the airport. • General Aviation Airport Air Monitoring Study (SCAQMD 2010). The goal of the study was to characterize the ambient levels of several important air toxics and ultrafines in communities adjacent to Van Nuys Airport (VNY) and Santa Monica Municipal Airport (SMO). • Teterboro Airport Detailed Air Quality Evaluation (ENVIRON 2008). The study involved mea- surements of various pollutants including volatile organic compounds (VOCs) and PM to investigate health risks associated with airport operations. • ACRP Report 7: Aircraft and Airport-Related Hazardous Air Pollutants (Wood 2008). San Leandro Measurements: After JETS-APEX2, the Aerodyne Mobile Laboratory spent 2 days at the San Leandro Marina, which is about 2 km downwind of the OAK runway. • Aircraft Emissions’ Contributions to Organic Aerosols in a Regional Air Quality Model Using the Volatility Basis Set (Woody 2012). The focus of this work was to estimate contributions of aircraft emissions from ATL to PM2.5, focusing on organic aerosols, using a research version of CMAQ v4.7. • Relationships between Emissions-Related Aviation Regulations and Human Health (Sequeira 2008). The study was conducted under the Energy Policy Act of 2005 to assess aircraft impacts on air quality in the United States. • Risk Factors of Jet Fuel Combustion Products (Tesseraux 2004). Using available monitoring data, the possibilities and limitations for a risk assessment approach were determined for the popula- tion living around large airports. Measurement data from German airports at Frankfurt and Hamburg, as well as from ORD, were presented (Spicer 1994, Eickhoff 1998, and EPA 2002). • Detecting and Quantifying Aircraft and Other On-Airport Contributions to Ambient Nitrogen Oxides in the Vicinity of a Large International Airport (Carslaw 2006). Based on concerns over the building of a third runway at London-Heathrow International Airport (LHR), data from NOx monitoring sites near the airport were used to assess contributions by the airport. • LAX Air Quality and Source Apportionment Study (Tetra Tech 2013). The Los Angeles Inter- national Airport (LAX) Air Quality Source Apportionment Study (AQSAS) was conducted to measure criteria pollutant HAP concentrations in the vicinity of LAX and to assess the potential impacts of airport-related emissions on ambient air quality of communities adja- cent to the airport.

Current Understanding of Airport Air Quality Health Impacts 35 • Current and Future Particulate-Matter-Related Mortality Risks in the United States from Aviation Emissions during Landing and Takeoff (Levy 2012). A study was conducted to systematically quantify aviation contributions to air quality concentrations and corresponding public health effects using 99 airports. • Development and Evaluation of an Air Quality Modeling Approach to Assess Near-Field Impacts of Lead Emissions from Piston-Engine Aircraft Operating on Leaded Aviation Gasoline (Carr 2011). A new methodology is presented on modeling the dispersion of lead emissions from general aviation aircraft. These example studies illustrate the fact that recent and current research tends to follow the pollutant prioritization scheme previously discussed (i.e., significant focus on PM). Although more research is necessary, the information gathered from existing studies allows for a snapshot- in-time summary of airport impacts. This is a temporary summary since further research is expected, including both measurement and modeling efforts. In particular, measurements will be necessary to help assess actual conditions at an airport, as well as to validate modeling efforts. Based on the research work conducted thus far, it is expected that as the research work con- tinues, some of the details may become clarified and corrected, but many of the more general understandings will likely remain intact. Along those lines, one of the first general issues is whether airports have a discernible influ- ence on local air quality. Some studies have indicated that pollutant concentration levels near an airport are similar to urban levels (e.g., Tesseraux 2004, McGulley 1995, and KM Chng 1999), which can result in a misunderstanding that airports overall contribute little or no pollutants to local air quality. Contrary to this, there have been several measurement studies that indicate that concentrations around airports are elevated (e.g., Wood 2008, RIDEM 2008, Zhu 2011). Depending on the pollutant, the contributions may range from a small or negligible contribu- tion (e.g., some criteria pollutants and HAPs species) to significant contributions (e.g., ultrafine particles). Also, background concentrations may affect pollutants through chemical conver- sions. In addition, various modeling studies have quantified the concentration contributions and associated health risks (e.g., Levy 2008, Sequeira 2008, and Barrett 2012, etc.) Modeled estimates and measured findings for the specific contributions to local air quality and health impacts are varied and depend on pollutants. The focus of each study—which pollutants and heath assessments were included and which were left out—also is important. The following summaries provide examples of quantified airport contributions to ambient concentrations as well as health-related statistics. • On a national level, the modeling study conducted under PARTNER Project 15 (Ratliff 2009 and Sequeira 2008) found aircraft emissions contributing to the following criteria pollutant concentrations: – Annual PM2.5: 0.01 µg/m 3 (0.08 percent) and – 8-hour ozone: 0.10 ppb (0.12 percent). These contributions represent averages across the U.S. airports selected for this study. As such, individual airports may experience significantly different outcomes. Although there have been differing conclusions from past studies, the prepon- derance of the evidence appears to indicate the concentrations of pollutants (depending on the pollutant) are generally elevated in the vicinity of airports.

36 Understanding Airport Air Quality and Public Health Studies Related to Airports • Measurements were conducted at Dulles International Airport (IAD) on the airside adjacent to an apron area (Kim et al. 2012). The measured 1-hour concentrations for criteria pollutants were all much lower than the NAAQS, and in most cases, much lower: – NO2: Typically below 30 ppb, – CO: Typically below 1 ppm, – SO2: Typically below 3 ppb, – O3: Typically below 20 ppb in the winter and below 50 in the summer, and – PM2.5: Typically below 25 µg/m 3 (24-hour samples). These measured levels seem to suggest that the airport’s contributions to local air quality tend to be small. • The measurements and modeling conducted under the LAX Source Apportionment Study provided a lot of detailed information. A summary follows (Tetra Tech 2013): – CO, NO2, SO2, and Pb ambient concentrations within the communities next to LAX were below threshold levels for state and national standards. – PM2.5 concentrations were near air quality standard levels and had compositions of 77 50–75 percent ammonium nitrate, ammonium sulfate, and unapportioned organic matter; 77 20–30 percent sea salt aerosol, soil-derived fugitive dust, and wood smoke; 77 1–2 percent jet exhaust; and 77 8–17 percent diesel plus gasoline vehicle exhaust. – Airport PM2.5 concentration contributions were estimated to be 5–20 percent. – CMAQ modeling showed most of the nitrates, sulfates, and most of the residual organic matter were formed outside of the study area. – Winter: airport accounted for 15–22 percent of CO and NOx concentrations. – Summer: airport accounted for 40–50 percent CO and 50–74 percent NOx concentrations at some measurement sites. – Airport SO2 contributions ranged from 10–80 percent depending on season. – HAP concentrations were consistently lower than the levels found elsewhere in the basin area. – The generally low concentration levels can be attributed to the coastal location of LAX. – Ultrafine composition was found to be largely composed of sulfuric acid aerosols from jet exhaust and their number concentrations east of LAX were found to be higher than typical values in the region. • Using measured data near LHR, Carslaw et al. (2006) found that aircraft NOx concentrations could be detected at least 2.6 km from the airport. At the airport boundary, approximately 27 percent of the annual mean NOx and NO2 concentrations were found to be due to aircraft. At distances of 2 to 3 km downwind of the airport, an upper limit of 15 percent contribution from the airport was estimated. • Ellerman et al. (2010) used measurement data from Copenhagen Airport to show that the number of ultrafine particles (43,000 particles/cm3) in an apron area was approximately The airport concentrations (largely monitored data) presented herein were obtained from publicly available documents for illustration purposes to summarize and help expand the understanding of airport contributions to local air quality. Since most of the cited studies were research efforts, the concentrations should not be taken out of context and used for regulatory purposes. For further details and to understand the context of each dataset, it is recommended that the cited sources be reviewed accordingly.

Current Understanding of Airport Air Quality Health Impacts 37 4.4 times greater than the levels found at a background site (near a major roadway). In contrast, a site located on the east side of the airport (closer to the airport boundary) expe- rienced 12,000 particles/cm3 or 22 percent higher than the same background concentration. The study also found that 90 percent of the particles were in the lower end of the ultrafine size range of 6–40 nm. • From measurements downwind of Santa Monica Municipal Airport (SMO), Hu et al. (2009) found elevated concentrations of ultrafine particles beyond 660 m downwind of SMO. At distances of 100 and 660 m downwind, respectively, ultrafine concentrations were found to be 10 and 2.5 times greater than background levels. • Using measured data near runways at LAX, Hsu et al. (2013) observed median ultrafine particle concentrations of 150,000 particles/cm3. In some cases, concentrations exceeded 1,000,000 particles/cm3, which is far in excess of levels seen near roadway sources. However, the concentrations were observed to drop rapidly with distance—by an order of magnitude before reaching the airport boundaries. • Based on data collected at the LAX blast fence (downwind sites up to 600 m from a runway and upwind of a major runway), Zhu et al. (2011) found high spikes in ultrafine particle concentrations. Time-averaged concentrations of PM2.5, two carbonyl compounds, form- aldehyde, and acrolein, were found to be elevated compared to background levels. As ultrafine particle and black carbon levels have previously shown to return to background levels at 300 m downwind for roadway sources, the persistence of airport ultrafine concentrations up to 600 m seem to indicate that airport emissions may have a broader spatial impact than roadway sources. • Using data from a monitoring study in the vicinity of LAX, Westerdahl et al. (2008) found the following: – Upwind site: 77 Ultrafine particles ranged from 58 to 3,800 particles/cm3 at below 90 nm size, 77 NOx ranged from 4–22 ppb, 77 BC ranged from 0.2–0.6 µg/m3, and 77 PM-PAH ranged from 18–36 ng/m3. – Downwind site: 77 Ultrafine particles—50,000 particles/cm3, 500 m downwind at 10–15 nm size and 77 Black carbon, PM-PAH, and NOx levels were “elevated to a lesser extent.” • A monitoring study near PVD showed the following results (Rhode Island 2007): – None of the HAP species measured exceeded the acute health and non-cancer benchmarks. – Concentrations of benzene, 1,3-butadiene, formaldehyde, acetaldehyde, acetone, chloro- form, carbon tetrachloride, and perchloroethylene exceeded the cancer benchmark levels. – Formaldehyde concentrations at all sites were greater than 10 times the cancer risk benchmark. Particles/cm3 is a measure of the number of particles over a unit volume (particle concentration) and should not be confused with PM mass concentrations such as µg/m3. Particles/cm3 cannot be converted to mass concentrations without the use of (or assumptions involving) the density of the particles. It also should be noted that particle counting equipment does not typically differentiate between primary and secondarily formed particles (i.e., particles formed in the atmosphere). As such, studies that do not explicitly account for the effects of secondary particles may overestimate the number of particles.

38 Understanding Airport Air Quality and Public Health Studies Related to Airports – Acetaldehyde and acetone were 2.5–3 times higher than the cancer risk benchmark. – Black carbon concentrations in communities were higher in areas near roadways. – Although a non-reference method (with a bias towards higher readings) was used to mea- sure PM2.5, the levels were still below the NAAQS in the communities near the airport. Airport contributions could be identified based on the fidelity of the monitors. • Based on data collected during a monitoring study around VNY and SMO, the following were found (SCAQMD 2010): – The daily average TSP lead concentrations at airport sites were 2–9 times higher than cor- responding South Coast Basin levels and mostly below the NAAQS. But 24-hour concen- trations at SMO near the tarmac were found to be above the NAAQS on more than one occasion. – The highest VOC concentrations at the airport sites were comparable to levels found at urban monitoring sites. – PM2.5 concentration levels, as well as those of organic carbon (OC) and elemental carbon (EC), were found to be similar or below the corresponding South Coast Basin averages. – Ultrafine particle numbers measured near a runway were found to be up to 600 times that of background air. – Diurnal profiles suggest that CO concentrations may be mostly due to motor vehicles from surrounding roadways rather than the airport. • From ambient measurements taken at the San Leandro Marina (Wood 2008), the average HCHO concentration in a time series is 1.3 ppb while the interpolated background value is approximately 0.8 (similar to the background value observed on the OAK airport grounds). • On a national level, a system-level health risk assessment study (Levy 2012) using CMAQ and appropriate concentration response functions (CRF) to model baseline and future scenarios determined that national population health impacts would increase by a factor of 6.1 from 2005 to 2025. This was based on a notional “what if” aviation growth scenario and corre- sponding emissions assumptions. The factor of 6.1 increase was decomposed into the follow- ing contributing factors: – Emissions: 2.1; – Population factors (growth and aging): 1.3; and – Changing non-aviation concentrations, enhancing PM2.5 formation: 2.3. • A study analyzing HAP emissions from ORD and related health risks (ENVIRON 2000) showed that HAPs concentrations measured at the airport fence area may result in about 5 times higher cancer risks than those associated with background air. The most significant contributing HAPs such as aldehydes, benzene, and naphthalene are included in aircraft emissions. • Based on a health impact study of U.K. airport expansions, especially LHR (i.e., third run- way), the following results were estimated (Barrett et al. 2012 and Yim 2013): – Approximately 110 people in the United Kingdom die early each year due to airport emis- sions today. Of these deaths, approximately 50 are due to emissions from London Heathrow. – By 2030, without airport capacity expansion, the number of early deaths per year caused by U.K. airport emissions is projected to increase to 250. • For an airport occupational exposure study (Tunnicliffe et al. 1999) conducted at Birmingham International Airport, U.K., it was found that the results appear to support an association between high occupational exposures to aviation fuel or jet stream exhaust and excess upper and lower respiratory tract symptoms for airport male workers. However, it is acknowledged that there could have been some bias effects such as residual confounding due to smoking. These example findings illustrate the types of quantitative and investigative studies that have been conducted on airport air quality health impacts. They also illustrate that airport concentration contributions and health impact statistics are closely related. Although the types and scope of these studies vary, they help to form a picture of the current understanding of airport health impacts.

Current Understanding of Airport Air Quality Health Impacts 39 5.2.2 Summaries and Conclusions In summary, it should be noted that all pollutants emitted from airports have some level of toxicity with the potential to cause health effects. Again, each airport is different and can have significantly different emissions, weather patterns, geography, etc., from each other, resulting in different air quality contributions. With that in mind, the existing body of research appears to suggest the following for each pollutant (or category of pollutants): • Most criteria gases (CO, NO2, and SO2)—In most situations, airport contributions of these pollutants appear to be such that resulting ambient community or urban concentrations are generally below the NAAQS. Depending on the pollutant and distances to the affected commu- nities, airport contributions of these pollutants may be relatively small. However, as studies have pointed out, the contributions can still be apportioned at relatively far distances (a few miles). While much of the health impact focus has been placed on PM and HAPs, it is worth re- membering that gaseous criteria pollutants can cause damage to the respiratory system. But the evidence supporting quantitative health risk assessment is more limited for CO, NO2, and SO2, relative to ozone and fine particulate matter. Although variability exists among airports, past studies seem to indicate that airport contributions of criteria gases generally tend to be small (or at least in most cases, not contributing to the point where the vicinity of an airport exceeds the NAAQS). Unlike criteria gases, PM2.5 concentrations in and around airports seem to vary significantly. Although health impacts of PM2.5 have been found to be higher than others, further research is necessary on the influence of PM chemical composition and size distribution. • In general, most studies suggest that ozone levels in the vicinity of airports will tend to be lower than background levels due to the chemistry with NOx. Because airports emit large quantities of NOx emissions, health assessments indicate the risks associated with airport indi- rect ozone contributions to local air quality are relatively small. However, the airport contri- butions to regional ozone can be greater and can contribute significantly to the overall health impacts of airport emissions. • Lead has been an emerging source of concern due to its toxicity and use at GA airports. Modeling and measurement efforts have shown that lead emissions from GA airports can persist up to 900 m downwind and may be above the background and the NAAQS. • PM2.5 or fine particles are a serious concern for health impacts as they dominate air quality health risks (e.g., by orders of magnitude over HAPs). The levels found in airport measure- ment studies vary, ranging from relatively low levels to those that are close to the NAAQS, and in some cases exceeding the standards. In addition to the variability of PM2.5 contributions, the various components and types of PM including black carbon, nitrates, sulfates, volatiles, etc., need to be recognized as well.

40 Understanding Airport Air Quality and Public Health Studies Related to Airports Modeling studies suggest that some of the PM (secondary PM) may form much farther downstream (many miles). As such, the total health impacts from airport-emitted PM and PM precursors requires regional-scale atmospheric modeling. Also, although the general health effects of PM regarding both morbidity and mortality are established, there is greater uncertainty regarding the influence of chemical composition and size distribution of PM on health outcomes. PM10 is also a health concern, but because coarse particles (PM10-2.5) are filtered to a greater extent by the upper respiratory tract in humans, there is less focus on its impacts. • Ultrafine PM is a suspected major health concern but there is little data available on both particle concentrations and resulting health effects. However, existing studies indicate that ultrafine particle concentrations are highly elevated at an airport (i.e., near a runway) with particle counts that may be orders of magnitude higher than background with some persistence many meters downstream (e.g., 600 m). Although ultrafine PM is a suspected major health concern, there is little data currently—more research is necessary. But from existing studies, ultrafine levels have been found to be elevated (above background levels) in the vicinity of airports. As with other pollutants, more studies are necessary to measure concentration levels of HAPs near airports. Although some studies indicate that HAP emissions from airports may be negligible (i.e., resulting in concentrations comparable to background levels), there appears to be enough evidence that suggests otherwise. • While HAPs or air toxics have less risk than PM2.5, they still pose a health concern, in part due to the potential for cancer and premature death endpoints. Measurement studies indicate that concentration levels can vary significantly from one airport to another. Although some studies suggest monitored concentrations may be comparable to background levels (depending on where the measurements were conducted), there is also enough evidence to suggest that airport contributions are not negligible.

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TRB’s Airport Cooperative Research Program (ACRP) Report 135: Understanding Airport Air Quality and Public Health Studies Related to Airports explores the following air quality issues: the literature regarding standards and regulations; issues at airports; health impacts and risks; and the industry’s current understanding of its health impacts.

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