ANNEX 1d to the Final Report of the SCOEL Support Project AA/31887/DF/EMPL - ARES 30/11/2010 – No 84933
Combustion Products from Aviation Fuels Scoping Study on behalf of DG EMPL
Ispra, September 2012
September 2012 Dimosthenis Papameletiou Dimosthenis Axiotis European Commission Joint Research Centre, Institute for Health and Consumer Protection, Chemical Assessment and Testing Unit (I.1) Competence Group: Risk Analysis, Ispra, Italy
Table of contents About the SCOEL support project ............................................................................................ vi Executive summary .................................................................................................................viii 1. Background ............................................................................................................................ 1 2. Setting the Priority on Ultra Fine Particles (UFPs)................................................................ 3 3. Existing legislation, OELs and key assessment studies ......................................................... 4 4. Characterization of airport emissions sources........................................................................ 6 5. Characterization of particulate aircraft emissions................................................................ 11 6. Characterization of airport PM air quality ........................................................................... 16 6.1 Case Study A: Airport El Prat, Barcelona...................................................................... 16 6.2 Case Study: Copenhagen Airport Kastrup ..................................................................... 17 6.3 Case Study: Los Angeles international airport (LAX)................................................... 19 7. Characterization of occupational exposures in airports ....................................................... 21 7.1 Case Study: Copenhagen Airport, Kastrup .................................................................... 21 7.2 Case Study: Aalborg Airport.......................................................................................... 23 7.2.1 Luggage handling.................................................................................................... 23 7.2.2 Luggage Hall........................................................................................................... 24 7.3 Case Study: Savannah air National Guard base, Georgia, USA .................................... 25 7.4 Case Study: Italian airport.............................................................................................. 27 7.5 Case Study: Italian aviation base ................................................................................... 27 7.6 Case Study: Taipei international airport......................................................................... 29 8. Biomonitoring studies .......................................................................................................... 32 9. Assessement of health effects .............................................................................................. 33 10. Epidemiologic evidence ..................................................................................................... 38 11. Risk management measures ............................................................................................... 40 12. Conclusions and recommendations.................................................................................... 43 References ................................................................................................................................ 45
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Acronyms 1-OHP – 1-Hydroxy-pyrene APU – Auxiliary Power Unit BC – Black Carbon CA – Chromosomal Aberration CD – Criteria Document CMAQ - Community Multiscale Air Quality model COPD - Chronic obstructive pulmonary disease DCE - Danish Centre for Environment and EnergyDSB - Double-Strand Breaks DLR – Deutsches Zentrum fur Luft und Raumfahrt (German Aerospace Center) EC – Elemental Carbon EEF – Engine Emission Factor ERO – Engine Running On/Off FOCA – Federal Office for Civil Aviation GC/MSD - Gas Chromatography/Mass Selective Detector GPU – Ground Power Unit GSE - Ground Service Equipment HC - HydroCarbon ICAO – International Civil Aviation Organization JRC – Joint Reasearch Center LTO - Landing and TakeOff MN - MicroNucleus MOUDI - Micro-Orifice Uniform Deposition Impactor OC – Organic Carbon OEL – Occupational Exposure Limit OELV - Occupational Exposure Limit Value
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OSHA – Occupational Safety and Health Administration PAS - Photoelectric Aerosol Sensor PAH – Polycyclic Aromatic Hydrocarbon PCA-MLRA - Principal Component Analysis - Multi-Linear Regression PM – Particulate Matter RMM – Risk Management Measure SCE – Sister-Chromatid Exchanges SCGE - Single-Cell Gel Electrophoresis SCOEL – Scientific Committee on Occupational Exposure Limits SIA - Secondary Inorganic Aerosols SS – Scoping Study SUM – Summary document TEF – Toxic Equivalent Factor TM – Tail Moment UFP – Ultra-Fine Particle VOCs – Volatile Organic Compounds
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ABOUT THE SCOEL SUPPORT PROJECT
The Commission has established and has been operating over the last two decades a Scientific Committee on Occupational Exposure Limits (SCOEL) in the framework of setting occupational exposure limit values (OELVs). The mandate of SCOEL is to examine available information on toxicological and other relevant properties of chemical agents, evaluate the relationship between the health effects of the agents and the level of occupational exposure, and where possible recommend values for occupational exposure limits which it believes will protect workers from chemical risks. Members of SCOEL are selected following an invitation from the European Commission to the Member States that requests the nomination of suitable candidates. All SCOEL members act as independent scientific experts, not as representatives of their national Governments. SCOEL membership includes, inter-alia, experts in chemistry, toxicology, epidemiology, occupational medicine and industrial hygiene. At national level, Member States active in the area of OELs – Occupational Exposure Limits development - have been setting up, in addition to their Scientific Committee, specific support infrastructures to tackle the production of criteria documents, which are basic inputs to the work of the Scientific Committees. At EU level, the operation of SCOEL has not been supported by such an infrastructure. The increasing amount of workload imposes to the Commission the need to outsource the preparation of preliminary scientific documents. These documents which were the basis for the scientific evaluation carried out by SCOEL have been prepared through studies by external experts. The scientific support to be provided by JRC will replace these studies and will provide a long term and more consistent scientific support to SCOEL. To this end, DG EMPL considered necessary to take a concrete initiative to set up a cooperation framework with JRC and requests the assistance of it for the establishment of a support activity for SCOEL in the JRC. The overall objective of the SCOEL support project is to develop at the JRC Institute of Health and Consumers Protection (IHCP), an infrastructure that will provide technical and scientific services to DG EMPL and to the SCOEL in the area of Occupational Exposure
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Limit Values (OELVs) for individual hazardous chemicals in the workplace in accordance with article 3 of Directive 98/24/EC on chemical agents and Directive 2004/37/EC on carcinogens and mutagens. The support activity is focused on the preparation of the following types of documents: •
Criteria Documents (CDs): summarize in a single document the entire relevant scientific information base for a given hazardous chemical that is available for the OEL setting by SCOEL.
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Summary Documents (SUMs): screen out the key information that is finally used for the derivation of a proposed OEL for a given hazardous chemical.
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Scoping Studies (SSs): are carried out in complex areas, where exploratory analysis is necessary for establishing the feasibility and specifications of future work on criteria documents.
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EXECUTIVE SUMMARY
Occupational exposures from combustion products from aviation fuels in airports is a complex area, where exploratory analysis is necessary for establishing the feasibility and specifications of future work by SCOEL on criteria documents and the setting of OELs at EU level. In this light, DG EMPL/SCOEL requested the JRC to carry out the present scoping study. Combustion products from aviation fuels in airports consist mainly of inorganic gases (CO, CO2, NOx, SO2), volatile organic compounds (VOCs), raw fuel, oxygenated organics, polycyclic aromatic hydrocarbons (PAHs), alcohols, ozone and particulate matter (PM). Several components of combustion products from aviation fuels are covered by generally applicable OELs. However, there is an emerging consensus that ultra fine particulate (UFP) emissions from aircraft and the related exposures of airport workers need to be tackled as the first priority. On this basis, the present report reviews the following topics with particular focus on UFPs: •
Aircraft emissions.
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Airport emission sources and air quality.
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Occupational exposures in airports and assessment of health effects.
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Risk Management Measures (RMMs).
The report summarizes results from research activities over the recent two decades that have been devoted to the mechanisms of UFPs formation by aircraft engines and their further evolution in the exhaust plumes. The impact of these emissions on airport air-quality is illustrated by using case studies in several airports at world scale, such as Barcelona, Copenhagen, Los Angeles with focus on air quality with respect to UFPs and the association to aircrafts as a key emission source. The Danish Ecocouncil (2012) and Aarhus University/DCE (2011) provide a comprehensive case study of the Copenhagen airport. The results show that the average workers exposures to UFPs in this airport are more than twice the maximal exposure on city streets with heavy traffic and up to 50 times higher than the typical office employees. Our study further reviews available international case studies in airports in Italy, USA and Taiwan.
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The assessment of the health effects caused by UFPs in airport occupational settings was found to be in its infancy. First studies investigating occurrence of DNA-damages in airport workers were carried out by Cavallo et al. (2002) and Pitarque et al. (1999). Furthermore, the study by The Danish Ecocouncil (2012) refers to “The National Board of Industrial Injuries” in Denmark that has recognised several cancer cases most likely caused by air pollution in airports. Results are also available from a recent study by Lai et al. (2012) at the international airport in Taipei. This study carried out an assessment of the carcinogenic potency of particulate-bound PAHs that were measured in the Taipei airport. The assessment method of the carcinogenic potency was based on the use of benzo[a]pyrene equivalent concentrations (BaPeq). The study concluded that a possibility of long-term adverse health effects exists following chronic exposure by inhalation by personnel working at the airport apron. Epidemiologic assessments of the UFP exposures in occupational airport settings are not yet available. A first systematic cohort study was announced in Denmark that will be carried out from 2012-15 to clarify illness among present and former employees in the airport (The Danish Ecocouncil, 2011). In light of the existing data on occupational exposures to UFPs in airports and the related assessments and epidemiologic evidence on the health impacts, the present report estimates that there is a limited information basis for setting health based OELs. Data are particularly lacking regarding the toxicity of UFP emissions from aircrafts. However, existing and emerging data on the health effects from particulate-bound PAHs, the occurrence of DNAdamages in airport personnel and the announced first systematic cohort study in Denmark may offer first opportunities for further action. Finally, the study documents and recommends application of risk management measures (RMMs) that have been proposed by ICAO (2011) and The Danish Ecocouncil (2012).
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1. BACKGROUND
Occupational exposure of workers in airports hasn't attracted a lot of interest in the history of aviation. The main concerns were related to passenger safety and a lot of effort has been put to improve flight procedures and standards. However, fast increase of passenger air traffic started to effect local air quality. In the late 1950s and 1960s vast improvements have been achieved by the introduction of jet commercial aircrafts replacing gradually the old higherpolluting fleet. Commercial jets have far improved engines' emissions but aviation is continuously growing. It is foreseen that passenger air traffic will be far increase within next years. Worldwide scheduled passenger air travel had a growth rate of over 8% per year between 1960 and 2005. Over the next decade it is forecast to grow by 4.5 – 6% per year (Stettler et al., 2011). Even if new technologies and standards improve engine emissions, evolution on low-emission engine design is relatively slow (e.g. compared to car engines). Indeed, the 25 – 30 year lifetime of airplanes will keep large numbers of today's polluting engines aloft long after technological solutions begin to make significantly cleaner engines available. Nevertheless, air-quality in airports is not only subject to aircraft emissions but also to airport ground service equipment (GSE), various ground transport travelling around and terminal maintenance and heating facilities. The International Civil Aviation Organization (ICAO) in its 2011 'Airport Quality Manual' addresses 'airport' as an assemblage of moving or mobile sources of emissions and stationary sources. Thus, for minimising occupational exposures it's critical to optimise airport design including layout and infrastructure, modification of operating practices for greater efficiencies, provision of the GSE fleet with no- or lowemitting technologies and promotion of other environmentally-friendly modes of ground transport. ICAO has established standards for the emissions of commercial aircraft engines since the late 1970s. The purpose of the standards is to limit the emissions of smoke, unburnt hydrocarbons (HC), carbon monoxide (CO) and oxides of nitrogen (NOx) from turbojet and turbofan aircraft engines (ICAO, 2008: Annex 16, Volume II). Aircrafts emissions are regulated bellow 3000 ft and an exception to the ICAO standards is all military aircrafts and their emissions. EU regulates the emission from road vehicles and from non-road vehicles (mobile machinery). All diesel engines used for handling and loading in the airport are subject to the
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directive for non-road vehicles. The 2008 ambient air quality directive (2008/50/EC) sets legally binding limits for concentrations in outdoor air of major air pollutants that impact public health such as particulate matter (PM10 and PM2.5), sulphur dioxide (SO2), benzene (C6H6), carbon monoxide (CO), lead (Pb) and nitrogen dioxide (NO2). Recent studies from Denmark (The Danish Ecocouncil, 2012) and Aarhus University (DCE, 2011) suggest that the main concern is related to ultrafine exhaust particles from aircrafts and diesel engines. Ultrafine diesel particles are known to cause cancer, heart disease, blood clots, brain haemorrhage and airway diseases (bronchitis, COPD), thereby increasing the risk of serious work related illness and premature death.
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2. SETTING THE PRIORITY ON ULTRA FINE PARTICLES (UFPS)
Combustion products from aviation fuels, relevant to the present study, mainly consist of the following chemical components (Ritchie, 2003): •
Inorganic gases: CO, CO2, NOx, SO2
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Volatile organic compounds (VOCs)
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Raw fuel
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Oxygenated organics
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Polycyclic aromatic hydrocarbons (PAHs)
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Alcohols
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Ozone
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Particulate matter
It appears that the aviation industry generally complies with existing regulations regarding the above substances. However, recent studies in Denmark, (The Danish Ecocouncil, 2012) and (DCE, 2011), suggest that pollution caused by aircraft in airports is a serious and overseen issue related to threats caused by ultra fine particles (UFPs) that are currently not covered by regulation. Persons working close to exhaust from aircraft engines (main engines and the APU: Auxiliary Power Unit) and/or diesel engines (vehicles, handling and loading equipment etc.) in airports are exposed to a complex mixture of potential health damaging air pollution. First studies investigating the occurrence of DNA-damages in airport personnel were carried out by Pitarque (1999) and Cavallo (2002; 2006; 2009). The study by The Danish Ecocouncil (2012) also refers to “The National Board of Industrial Injuries” in Denmark, which has recognised several cancer cases most likely caused by air pollution in airports.
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3. EXISTING LEGISLATION, OELS AND KEY ASSESSMENT STUDIES
Presently, the regulations and standards affecting airport sources of emissions and airport air quality typically fall into the following distinct categories: •
Measures that set limits on particular sources of emissions, including both aircraft engines and non-aircraft sources such as stationary facilities (e.g. boilers, generators, incinerator) and road vehicles, and
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Regulations establishing ambient pollutant concentrations for local air quality conditions (e.g. local air quality values).
A key assessment study regarding the establishment and implementation of both types of regulations on airport emission sources and the related air-quality was published by the International Civil Aviation Organization (ICAO) in 2011 (ICAO, 2011). Regarding occupational exposures, to our knowledge, regulations specific to airports have not yet been derived at world scale. However, several components of combustion products from aviation fuels are covered by generally applicable OELs. This is illustrated, in Table 1, on the example of Danish limit values for air pollution at workplaces compared to the general Danish (EU) minimum air quality limits in public locations (streets etc.). This comparison shows that exposures to ultrafine particles (UFPs) and nanoparticles are not covered by regulations for both workers and the general population.
Table 1. Danish limit values for air pollution at workplaces compared to the ambient air quality limits (The Danish Ecocouncil, 2012).
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On the issue of occupational exposures to ultrafine particles and nanoparticles, key assessment studies have been published recently in Denmark (DCE, 2011; The Danish Ecocouncil, 2012). These studies specify the lack of related regulations and provide occupational exposure data measured recently in Danish airports with the scope to contribute to the development and implementation of measures.
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4. CHARACTERIZATION OF AIRPORT EMISSIONS SOURCES
The sources of occupational exposures in airports include both airport and background (non airport) sources. The particular contribution of each type of the sources depends on a variety of parameters, such as geography, meteorology, urban settings and airport configuration. As an example to illustrate the quantification of the contribution of pollution sources to an airport we refer to the Copenhagen airport, for which a detailed study was carried out recently (Figure 1).
Figure 1. Sources of pollution in the Copenhagen airport (The Danish Ecocouncil, 2012). From the left side of Figure 1 it is clear that about 90 % of the ultrafine particles originate from sources in the airport. The opposite is the case for fine particles (PM 2.5) while NOx is more evenly distributed between sources both inside and outside the airport. From the right side of Figure 1, it is clear that diesel engines from handling are the dominant source in the airport contributing to pollution containing NOx and fine particles (PM 2.5). Unfortunately, a source apportionment regarding the sources of UFPs has not yet been carried out. Regarding NOx and fine particles, aircraft engines (main engines and APUs) were found to contribute significantly to airport pollution. The contribution from road traffic within the airport was found to be insignificant in the Copenhagen airport. The emission sources inside the airport, include both aircraft and non-aircraft sources such as stationary facilities and non-road vehicles. These emissions sources have been grouped by (ICAO, 2011) into four categories:
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aircrafts;
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aircraft handling operations;
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infrastructure- or stationary-related sources and
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vehicle traffic sources.
The aircraft emission sources typically include the exhausts from the: •
aircraft main engine, and
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Auxiliary Power Unit (APU)
Exhaust from the aircraft main engine: Main engines are used to propel the aircraft forward and are classified either as gas turbine turbofan (turbojet) and turboprop engines fuelled with jet fuel or combustion piston engines fuelled with aviation gasoline. They become a source of combustion emissions when they are in use during a number of non-ground and ground activities of the so-called Landing-Take-Off cycle (LTO cycle; Figure 2).
Figure 3. Landing - Take Off cycle (LTO cycle); engine thrust in (%); duration in (min) (Unique, 2012).
Aircraft emissions vary during the LTO cycle depending on the thrust and the duration of each operation. Specifically for the pollutant NOx, “Take-off roll” is the biggest emissions source (46%); though taxiing and use of auxiliary power units (APUs) are almost as large when considered together (Figure 3).
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In the cases of the Heathrow and the Zurich airports the relative contributions of each of the different sources to the total ground level emissions of NOx are illustrated in Figure 3. The key sources are clearly the aircrafts and the airport related traffic.
Figure 3. Estimated contributions of various sources to the total ground level NOx emissions around the Heathrow Airport (left) in 2008/2009 and the Zurich airport (right) in 2003 (Heathrow, 2011 and Unique, 2004).
Exhaust from the Auxiliary Power Unit (APU): An APU is a self-contained power unit on an aircraft providing electrical/pneumatic power to aircraft systems during ground operations. APUs are basically small turbine engine normally mounted in the rear fuselage of most transport category aircraft (Figure 4). They are used to power electrical systems on board, to run air circulation and conditioning systems and to supply bleed air for starting main engines before or during push back (AOA, 2010). APUs are principally smaller jet engines, they emit also PM, ultrafine particles, CO, VOCs, SOx, and contribute to ground level NOx emissions. As a Risk Management Measure (RMM), APUs could be substituted by ground powered systems (FEGP ‘fixed electrical ground power’ and PCA “preconditioned air”).
Figure 4. APU on a large commercial aircraft.
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Aircraft handling emissions sources are typically comprised of the following (ICAO, 2011): •
Ground support equipment: GSE necessary to handle the aircraft during the turnaround at the stand: ground power units, air climate units, aircraft tugs, conveyer belts, passenger stairs, forklifts, tractors, cargo loaders, etc (Figure 5).
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Airside traffic: Service vehicle and machinery traffic (sweepers, trucks (catering, fuel, sewage) cars, vans, buses, etc.) within the airport perimeter fence (usually restricted area) that circulate on service roads.
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Aircraft refuelling: Evaporation through aircraft fuel tanks (vents) and from fuel trucks or pipeline systems during fuelling operations.
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Aircraft de-icing: Application of de-icing and anti-icing substances to aircraft during winter
Figure 5. Pushback tractor, ground power unit (GPU) at the Amsterdam airport and right a step ladder. Infrastructure- or stationary-related source categories of emissions comprise the following (ICAO, 2011): •
Power/heat generating plant. Facilities that produce energy for the airport's infrastructure: boiler house, heating/cooling plants, co-generators.
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Emergency power generator. Diesel generators for emergency operations (e.g. for buildings or for runway lights).
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Aircraft maintenance. All activities and facilities for the maintenance of aircraft, i.e. washing, cleaning, paint shop, engine test beds.
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Airport maintenance. All activities for the maintenance of airport facilities (cleaning agents, building maintenance, repairs, greenland maintenance) and machinery (vehicle maintenance, paint shop). 9
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Fuel. Storage, distribution and handling of fuel in fuel farms and vehicle fuel stations.
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Construction activities. All construction activities associated with airport operation and development.
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Fire training. Activities for fire training with different types of fuel (kerosene, butane, propane, wood).
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Surface de-icing. Emissions of de-icing and anti-icing substances applied to aircraft moving areas and service and access roads
Vehicle traffic (associated with the airport on access roads): According to ICAO (2011) this gory includes motor bikes, cars, vans, trucks, buses and motor coaches, curbsides, drive-ups, and on- or off-site parking lots (including engine turn-off, startup and fuel tank evaporative emissions).
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5. CHARACTERIZATION OF PARTICULATE AIRCRAFT EMISSIONS
An introductory overview on particulate matter emissions from aviation is provided by (ACRP, 2008 and Petzold, 2005b), and is illustrated in the following Figures 6 and 7 regarding the particle sizes involved and the mechanisms of their evolution in the atmosphere.
Figure 6. Particle size of airport PM emissions (ACRP, 2008). There are different particle types involved, including the following: •
Solids
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Liquid droplets
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Combined solids and liquids.
These different particle types tend to have different sources and formation mechanisms: •
Coarse particles around airports originate from: wind blown dust, sea spray, salt storage piles, construction activity, crushing or grinding operations.
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Ultrafine particles can be: primary particles produced during combustion or newly nucleated (e.g. condensed) formed in the atmosphere or in aircraft plumes from condensable gases.
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OC – Organic Carbon EC – Elemental Carbon
Figure 7. Particle generation in aircraft engine and evolution in the exhaust (Petzold, 2005b).
Research into the particulate formation mechanisms from aircraft has been carried out intensively during the past decades. Key projects include the following (ACRP, 2008 and Petzold, 2005a; 2005b): •
SULFUR experiments (1994 - 1999), Deutsches Zentrum für Luft- und Raumfahrt (DLR) - led research: airborne experiments on the impact of the fuel sulphur content on the particle emissions of aircraft engines under cruise conditions.
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Partikel und Zirren (PAZI) (2000 - 2003), DLR- led research: German national programme on the investigation of the interaction of aviation-related particles and cirrus clouds, field studies, combustion experiments and aerosol chamber studies contributed.
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PartEmis (2000 - 2003), DLR- led research (Petzold, 2005a): EU funded experiment test rig studies on the impact of operation conditions, fuel sulphur content and turbine sectors on the properties of particles emitted from an aircraft engine.
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Apex1, (April 2004) USA: The Aircraft Particle Emissions eXperiment (APEX1) was the US first ground-based experiment to simultaneously examine gas and particle emissions from a modern commerce aircraft over the complete range of engine thrust settings.
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Delta Atlanta-Hartsfielsd Study, (September 2004) USA: was the first study to measure PM and gaseous emissions from in service commercial transports. The aircraft tested were selected from those scheduled to be overnight at the airport. The exhaust plumes of each aircraft were investigated using both probe sampling at the engine exhaust nozzle exit (Missouri S&T-ARI), and remote sensing using LIDAR (light detection and ranging) (NOAA) at a point in the plume close to the exhaust nozzle exit, thus permitting comparisons of measurement techniques. Another objective was a study of engine-to-engine variation within the same class and, where possible, two aircraft with the same engine class were studied.
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Jets-Apex2, (2005), USA: The project consisted of two series of experiments similar to the Delta Atlanta-Hartsfield study. The first series focused on PM emissions in the vicinity of the exhaust nozzle of several different aircraft whose engines were cycled through a matrix of reproducible engine operating conditions as in APEX1. The second series focused on emissions generated under actual operational conditions, conducted by placing the mobile laboratories adjacent to, and downstream of, active runways. In these latter measurements, advected exhaust plumes generated by the mix of commercial transport aircraft taxiing and departing the airport during normal operations were detected and analyzed.
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Apex3, (2005), USA: In this project, as in the three previous US studies, engine exhaust emissions and plume development were examined by acquiring data from the exhaust nozzle and in the near-field plume from a range of stationary commercial aircraft. A complementary study of downwind plumes during normal operations was abandoned because the prevailing winds during the scheduled sampling times did not transport the plumes to the available sampling locations.
The results of the DLR- led research activities were summarised by Petzold (2005a) as follows: •
Aircraft engines and most likely APU's as well are emitting volatile and non-volatile particles in the nanometre size range which are highly relevant concerning air quality issues.
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The emission of non-volatile combustion particles is a property of the engine itself while the emission of volatile particles depends on fuel composition and sample treatment.
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The process of developing recommendations for particle measurements in the exhaust of gas turbines is being initiated.
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Emission properties of aircraft engines concerning volatile and non-volatile particles are characterised; similar information for APU's is not available.
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Concerning the effect of particle emissions from aircraft engines and APU's on airport air quality, particularly with respect to source apportionment, dedicated field experiments are required.
The results of the US projects APEX 1-3 were reviewed and presented by Kinsey et al. (2010 & 2011). In total, the fine particulate matter (FPM) emissions from nine commercial aircraft engine models were determined by plume sampling during the three field campaigns of the Aircraft Particle Emissions Experiment (APEX). Ground-based measurements were made primarily at 30m behind the engine for PM mass and number concentration, particle size distribution, and total volatile matter using both time-integrated and continuous sampling techniques. The experimental results showed a PM mass emission index (EI) ranging from 10 to 550 mg/kg fuel depending on engine type and test parameters as well as a characteristic Ushaped curve of the mass EI with increasing fuel flow for the turbofan engines tested. Finally, the particle size distributions of the emissions exhibited a single primary mode that were lognormally distributed with a minor accumulation mode also observed at higher powers for all engines tested. The geometric (number) mean particle diameter ranged from 9.4 to 37 nm and the geometric standard deviation ranged from 1.3 to 2.3 depending on engine type, fuel flow, and test conditions. The 2011 APEX paper by Kinsey et al. (2011) addresses the need for detailed chemical information on the fine particulate matter (PM) generated by commercial aviation engines. Regarding the chemical composition of particulates in aircraft emissions in relation to occupational exposure in airports there has been some focus on particle-bound PAHs using photoelectric aerosol sensor (PAS) measurement techniques (Childers et al., 2000). These techniques provided a semi-quantitative temporal profile of ambient PAH concentrations and showed that PAH concentrations can fluctuate rapidly from a baseline level 4,000 ng/m3 during flight-related activities. Small handheld models of the PAS monitors exhibited potential for assessing incidental personal exposure to particle-bound PAHs in engine exhaust and for serving as a real-time dosimeter to indicate when respiratory protection is advisable.
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In conclusion, based on the currently available results on the particle generation mechanisms and the characterization of emissions from aircrafts, there appears to be agreement on existing knowledge gaps and future research priorities on the following broad lines: •
Improved source characterization, including aircrafts, APUs, GSE, tire, brake emissions.
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Improved particle size and chemical characterization of emission.
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Development of emission fingerprints and source apportionment.
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Harmonization of measurement and calculation methods.
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Investigation of the atmospheric evolution of aviation PM to identify properties at the point of exposure.
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6. CHARACTERIZATION OF AIRPORT PM AIR QUALITY
There is a wealth of airport air quality data on particulate matter mainly focused on PM 10 and PM 2.5. In general, this data shows compliance with established air quality standards. An illustration is provided in Figure 8 on the example of Heathrow airport, which shows annual mean concentrations of PM2.5 measured at Green Gates, Oaks Road, Harlington and LHR2 in 2010 were less than half of the EU target of 25 µg/m3.
Figure 8. Annual average gravimetric PM2.5 measurements at Heathrow's monitoring sites from 2002 to 2010 (Heathrow, 2011). Regarding particle sizes below PM2.5, there is a very limited data base. Below, we have compiled three different case studies describing the current state of knowledge: •
Airport El Prat, Barcelona: PM10, PM2.5, PM1.
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Copenhagen airport Kastrup: ultra fine particles.
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Los Angeles international airport (LAX): ultra fine particles.
6.1 Case Study A: Airport El Prat, Barcelona Monitoring of aerosol particle concentrations (PM10, PM2.5, PM1) and chemical analysis (PM10) was undertaken at El Prat, Barcelona, for a whole month during autumn, (Amato et al., 2010). Concentrations of airborne PM at the airport were close to those at road traffic
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hotspots in the nearby Barcelona city, with means measuring 48 mg PM10/m3, 21 mg PM2.5/m3 and 17 mg PM1/m3. Meteorological controls on PM at El Prat are identified as cleansing daytime sea breezes with abundant coarse salt particles, alternating with nocturnal land-sourced winds which channel air polluted by industry and traffic (PM1/PM10 ratios > 0.5) SE down the Llobregat Valley. Chemical analyses of the PM10 samples show that crustal PM is dominant (38%), followed by total carbon (OC + EC, 25%), secondary inorganic aerosols (SIA, 20%), and sea salt (6%). Local construction work for a new airport terminal was an important contributor to PM10 crustal levels. Source apportionment modelling PCAMLRA identified five factors: industrial/traffic, crustal, sea salt, SIA, and K likely derived from agricultural biomass burning. Whereas most of the atmospheric contamination concerning ambient air PM10 levels at El Prat is not attributable directly to aircraft movement, levels of carbon are unusually high (especially organic carbon), as are metals possibly sourced from tyre detritus/smoke in runway dust (Ba, Zn, Mo) and from brake dust in ambient PM10 (Cu, Sb), especially when the airport is at its most busy. The study identified micro-flakes of aluminous alloys in ambient PM10 filters derived from corroded fuselage and wings as an unequivocal and highly distinctive tracer for aircraft movement. Also, the OC concentrations observed were unusually high for a monitoring site not close to a major road, exceeding a roughly constant 2 mg/m3 the simultaneous concentrations registered at urban background. This suggests a possible contribution from aircraft exhaust, especially as these aerosols registered their highest levels when aircraft departures were also at their maximum. Another suggestion of atmospheric PM contributions sourcing directly from aircraft movements is the drop in Cu and Sb ambient air concentrations when landings were at their minimum, and the unusually high owe their origin at least in part to aerosols released by tyre abrasion and smoke during aircraft landing.
6.2 Case Study: Copenhagen Airport Kastrup Stationary air quality measurements were conducted in 2010-2011 in the Copenhagen airport. The purpose was to conduct detailed and long-term campaign of air pollution in the airport. The monitor station was placed in the airport yard close to the employees loading and handling aircrafts using gate B4; referred to as station B4 (Figure 9). At station B4 all groups of relevant pollutants were measured. Furthermore, NO2 and fine particles as well as ultrafine particles, were measured at station. East and West station are the
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official monitoring stations used in accordance with the environmental approval. Station West is close to houses in the residential area near the airport (Figure 9).
Figure 9. Localisation of ultrafine PM measurement stations at the apron of Copenhagen airport, Kastrup (The Danish Ecocouncil, 2012). DCE at University of Aarhus (DCE, 2011) performed all sampling and analyses connected to the stationary measurements. The analysed air samples from station B4 were taken 2.5 metres above ground level and analysed for 9 PAHs, 33 VOCs incl. 9 aldehydes, SO2, NOx, fine particles, ultrafine particles and soot (black carbon). The size interval for the measured particle number was 6-700 nm and will thereby include some particles larger than ultrafine particles (above 100 nm). However, the particle number is clearly dominated by particles below 100 nm and is not significantly influenced by particles from 100-700 nm (Table 2). Ultrafine particle size measurement results are presented in Figure 10. It is clearly seen, that the great number of particles at Station B4 is caused by a high number of the smallest particles from 6-40 nm. Station B4 was, furthermore, markedly higher than the other stations. The occurrence of a very high number of the smallest size fraction at Station B4 could presumably be explained by direct emissions from mainly jet motors. Station East is also
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influenced by these emissions, either via transport with the wind from the apron, or because of emissions from planes’ take-off or landing.
Table 2. Stationary measurements in Copenhagen Airport (The Danish Ecocouncil, 2012 & DCE, 2011).
All values in μg/m3 except ultrafine particles that are measured in number of particles per cm3. Measurements for Benz[a]pyrene, VOCs and SO2 are average levels over a month while values for NO2 and particles are average values over minimum half a year. Limit values: WP: Workplaces, PL: Public locations. HCAB: One of the most polluted city streets in Denmark, HCOE: building roof in Copenhagen and LV: Lille Valby in the open countryside. Ult. Part.: Ultrafine particles (6-700 nm) measured in particle number per cm3
Figure 10. Average particle-size distribution, measured at Station B4, Station East, street station HCAB and the regional background station at Lille Valby, Roskilde at the apron of Copenhagen Airport, Kastrup. The measurements were conducted from 28.07.2010 to 30.09.2010 (The Danish Ecocouncil, 2012).
6.3 Case Study: Los Angeles international airport (LAX) Westerdahl et al. (2008) carried out air monitoring in the vicinity of the Los Angeles international airport (LAX) during the spring of 2003. The purpose of this monitoring was to determine the extent of airport emissions on downwind ambient air in a mixed use 19
neighbourhood that includes residences. A mobile air monitoring platform was developed and deployed to measure ultrafine particle numbers, size distributions, particle length, black carbon (BC), oxides of nitrogen (NOx), and particle-phase polycyclic aromatic hydrocarbons (PM-PAH). Study results are illustrated in Figure 11.
Figure 11. Display of particle size distribution of clean coastal air, at various locations near LAX (Westerdahl et al., 2008). Pollutant levels were low at a coastal site upwind of the airport, with UFP ranging between 580 and 3800 counts cm-3, oxides of nitrogen (NOx) from 4 to 22 ppb, black carbon from 0.2 to 0.6 μg m-3, and PM-PAH ranged from 18 to 36 ng/m3. Markedly higher UFP counts, with average counts of approximately 50,000 cm-3, were observed at a site 500m downwind of the airport, which was strongly influenced by aircraft landings and where the community interfaced with airport facilities. Black carbon, PM-PAH, and NOx levels were elevated to a lesser extent at downwind locations. Transient peaks in UFP corresponding to aircraft landings and takeoffs were evident. A maximum UFP count reached 4.8 million particles cm-3 downwind of a runway used by jet aircraft for takeoffs. Particle size distributions differed substantially between upwind and downwind locations. The particle numbers at the upwind site were dominated by particles of approximately 90 nm diameter while downwind sites were dominated by particles peaking at approximately 10-15 nm. Additional data obtained from Biswas et al. (2005) levels indicates that aircraft-generated UFP persist up to 900m from an LAX runway.
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7. CHARACTERIZATION OF OCCUPATIONAL EXPOSURES IN AIRPORTS
Occupational exposures to UFPs in airports have been measured systematically, to our knowledge, only in few airports, about which we present the following case studies: •
Copenhagen Airport, Kastrup (chapter 7.1);
•
Aalborg Airport (chapter 7.2);
•
Savannah Air National Guard Base (chapter 7.3);
•
Italian Airport (chapter 7.4);
•
Italian Aviation Base (chapter 7.5);
•
Taipei International Airport (chapter 7.6).
7.1 Case Study: Copenhagen Airport, Kastrup Results of ultrafine particulate exposure measurements carried out in 2011 in baggage handler workplaces in the Copenhagen airport are presented in Table 3.
Table 3. Employee exposure to ultrafine particles in Copenhagen Airport (The Danish Ecocouncil, 2012).
The number of ultrafine particles is given as particle number per cm3. Concentrations from city streets are from the rush hours at two locations in Copenhagen, concentrations from office environments and the open countryside are from multiple measurements over several years.
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As a general conclusion, the Danish Ecocouncil stated, that “the employee exposure in the airport is much higher than on city streets with heavy traffic”. The average of all exposure measurements taken in the airport is higher than the measurement taken during rush hour on city streets with heavy traffic. The average maximum half hour exposure is more than twice the maximal exposure on city streets with heavy traffic. Many baggage handlers in the airport yard inhale about 25 times more ultrafine particles than a typical office employee, with some baggage handlers inhaling up to 50 times more ultrafine particles. The measurements clearly show large variations between the employee exposure, which reflects different activities occurring in the airport, the location and time of day. Figure 12 illustrates the employee exposure over 6 hours of work for a baggage handler. The figure shows that there are many different sources contributing to employee exposure in the airport and that variations over a working day are large, up to a factor 150; From approximately 3,000 particles per cm3 at 07:50 to about 445,000 particles per cm3 25 min. later. Hence, the levels of pollution can vary significantly. Some peak concentrations are easy to explain since the pollution source can be directly identified. On the other hand, the exposure from 09:10 to 09:40 contributes significantly to the total employee exposure (high concentrations for a long time), but no direct pollution sources can be identified, suggestive of the pollution is probably carried with the wind from one place to another in the airport. Aalborg airport
Table 12. Ultrafine Particulate measurements carried out at a “baggage handler” workplace, over six hours, in the Copenhagen Airport, (The Danish Ecocouncil, 2012).
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Furthermore, it is seen that the concentration level of ultrafine particles in a confined smoking room is approximately the same as the concentration levels originating from aircrafts and diesel engines in the airport. Finally, the data shows that throughout much of the day a baggage handler is exposed to higher levels of ultrafine particles than those found on city streets with heavy traffic during rush hour. Further measurements were carried out at various workplace areas in the Copenhagen airport, including: •
Garbage trucks
•
Car repair/garage
•
Fire stations
The measurements demonstrated that employees in various workplaces are exposed to ultrafine particles. The results are presented in Table 4.
Table 4. Ultrafine particulate measurements carried out at various workplace environments in the Copenhagen airport (The Danish Ecocouncil, 2012).
These groups seem to be exposed to lower concentrations than baggage handlers. However, according to The Danish Ecocouncil, they are exposed to similar concentrations as those found during rush hour on city streets with heavy traffic, which is also cause for concern. Additional measurements taken in public areas in the airport buildings were low, and comparable to other public buildings.
7.2 Case Study: Aalborg Airport 7.2.1 Luggage handling Figure 13 shows measurements of employee exposure during a luggage handling in Aalborg airport compared to concentrations found during the rush hour on streets with heavy traffic in
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Copenhagen (Norre Sogade). In the time between peaks 3 and 4, the concentration of ultrafine particles does not fall below the concentration on city streets with heavy traffic. This is due to pollution from diesel engines used for handling and loading. The Danish Ecocouncil (2012) concludes that from the measurements in Aalborg Airport it is clear that even in small airports with almost optimal dilution conditions serious exposure of employees to ultrafine particles can occur.
1: aircraft taxiing (by the main engines) to take off 2: aircraft from an adjacent gate turning on its APU 3: aircraft turning on its main engines and taxiing to take-off 4: aircraft just handled turning on its APU
Figure 13. Employee exposure during a 22 minutes long handling in Aalborg airport. Handling is the service in and around the aircrafts, which occurs at arrival and departure; (The Danish Ecocouncil, 2012).
7.2.2 Luggage Hall Figure 14 shows measurements of ultrafine particles from the luggage hall in Aalborg airport comparing ‘closed gate’ and ‘open gate’ (sunny days to avoid overheating) to the hall from 12 minutes before take-off until 16 minutes after take-off. It is clear that the gate should be closed to shield against ultrafine particles. With a closed gate the average concentration of ultrafine particles is about 18,000 particles per cm3, whereas the average concentration with an open gate is about 142,000 particles per cm3. The gate reduces exposure in the luggage hall by almost 90 percent during a typical take-off pollution period.
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Figure 14. Number of ultrafine particulates per cm3 in the luggage hall of the Aalborg airport, with closed and open gate, (The Danish Ecocouncil, 2012).
7.3 Case Study: Savannah air National Guard base, Georgia, USA Childers et al. (2000) carried out airborne particle-bound PAHs measurements using a photoelectronic sensor (PAS) technique. The study included an exposure assessment of flight personnel to PAHs, which
was conducted during a USAF-sponsored engine emission
surveillance of C-130H aircraft flight crews and ground personnel during various training exercises at the Savannah air National Guard base, Savannah, Georgia, from 4 to 6 May 1999. Measurements of airborne PAHs concentrations included locations and events, such as •
a break room,
•
downwind from a C-130H aircraft,
•
during a four-engine run-up test,
•
maintenance hangar,
•
cargo bay of a C-130H aircraft during cargo-drop training exercises,
•
downwind from aerospace ground equipment (AGE), and in the,
•
cargo bay of a C-130H aircraft during an engine running on/off (ERO) loading manoeuvre and backup.
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The results are presented in Table 5 for selected PAHs in comparison to OSHA target concentrations.
Table 5. Comparison of selected PAH exposure concentrations with OSHA target concentrations (Childers et al., 2000).
In general, the average concentrations of the five target PAHs in integrated-air samples associated with different aircraft exhaust monitoring events were appreciably lower than the OSHA target concentrations for coal tar pitch volatiles. Likewise, the mean values for particle-bound PAHs as measured by the PAS2000CE monitors were below the individual target concentrations of pyrene, chrysene, and benzo[a]pyrene, which are expected to be in the particulate phase. The highest potential for flight crew and ground-support personnel exposure occurred during the four-engine run-up tests, the ERO-loading exercises, and the reverse taxi manoeuvre with the cargo ramp door down. The real-time monitor response during these events often exceeded the upper limit of the dynamic range of the instruments, so a definitive assessment of the exposure cannot be made based on the real-time monitor response alone. The average concentrations of the target PAHs in the integrated-air samples during the four-engine run-up test and the ERO-loading exercise were approximately 10 (engine run-up) to 25 (ERO-loading) times higher than the average concentrations measured in a 24-hr air sample near a residential site in a metropolitan area during the heating season. In comparison, the target PAH concentrations in the integrated-air samples collected in the maintenance hangar during the taxi and takeoff maneuvers were approximately equal to the average indoor PAH concentrations in residences in a major city.
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7.4 Case Study: Italian airport The aim of the study by Iavicoli et al. (2006) was to use environmental monitoring to evaluate occupational exposure to polycyclic aromatic hydrocarbons (PAHs) and biphenyl in an Italian airport. Air was sampled using a quartz fiber filter, a polyurethane foam, and an XAD-2 layer. After extraction with dichloromethane, concentration and purification analyses of 25 PAHs (including biphenyl) were carried out by gas chromatography-ion trap mass spectrometry. In winter 2005, 12 air samples were taken at 120 L/min for 24 hours in three different areas of the airport. PAH levels were found to be generally low. In all investigated areas, the higher levels refer to naphthalene (130-13,050 ng/m3), 2-methylnaphthalene (64-28,500 ng/m3), 1methylnaphtalene (24-35,300 ng/m3), and biphenyl (24-1610 ng/m3). However, in some instances, for compounds such as benzo[b+j+k]fluoranthene and benzo[a]pyrene, two highboiling PAHs, the levels found (54.2 ng/m3 and 8.6 ng/m3, respectively) can be considered of some concern. The authors report that their findings are in agreement with the results obtained by Childers et al. (2000) (see chapter 7.3). Although both studies were carried out under substantially different conditions, the observed agreement refers to the PAHs profiles of two-ringed PAHs such as naphthalene, 1-methylnaphthalene, and biphenyl. In fact, in both studies naphthalene and methylnaphthalenes are the main components of the airborne PAH mixture. However, in the Italian study, both two-ringed PAHs were only found as vapour or lost from the filter onto sorbents during sampling.
7.5 Case Study: Italian aviation base In the study by Buonanno et al. (2012) the occupational exposure to airborne particles and other pollutants in a high performance jet engine airport was investigated. Three spatial scales were considered: i) a downwind receptor site, ii) close to the airstrip, iii) personal monitoring (Figure 15). Particle number, surface area, mass concentrations and distributions were measured as well as inorganic and organic fractions, ionic fractions and PAHs. Particle number distribution measured at a receptor site presents a mode of 80 nm and an average total concentration of 6.5 x103 part. cm3; the chemical analysis shows that all the elements may be attributed to longrange transport from the sea. Particle number concentrations in the proximity of the airstrip show short term peaks during the working day mainly related to takeoff, landing and pre27
flight operations of jet engines. Personal exposure of workers highlights a median number concentration of 2.5x104 part./cm3 and 1.7x104 part./cm3 for crew chief and hangar operator.
Figure 15. Sampling sites at the Italian aviation base (Buonanno et al., 2012).
Two kind of workers were selected that could be exposed in their activities: i) the crew chief who assists the pilots during the ground activities abreast the engine jet and ii) the hangar operator who works in the hangar in maintenance the aircraft not far from the area where the ground activities of the departing jet engine aircrafts take place. For each worker, about 10 daily samples of UFP concentrations were taken during the whole working period: a selected time series of particle number concentrations from July 28th continuously measured is reported in Figure 16. Particle number concentrations measured in the vicinity of the airstrip present several main short term peaks, during the working day, related to takeoff and landing of jet engine aircrafts as well as pre-flight operations. Moreover, the corresponding particle number distribution evolutions show that the mode is around 25 nm. The monitoring at personal scale showed that the highest exposure is experienced by crew chiefs even if it is not worrisome if compared to urban area one. In conclusion this work emphasizes the negligible impact of the airport under study mainly due to the atmospheric dilution and to the low number of daily flights in respect to civil airport.
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Figure 16. Time series of particle number concentrations continuously measured on July 28th at sites 1 and 2 as well as personal monitoring data. Peaks related to pre-flight operations, takeoff and landing of jet engine aircrafts are shown (Buonanno et al., 2012).
7.6 Case Study: Taipei international airport Concentrations of 22 polycyclic aromatic hydrocarbons (PAHs) were estimated for individual particle-size distributions at the airport apron of the Taipei international airport, Taiwan, in July, September, October, and December of 2011 (Lai et al., 2012). The sampling site is shown in Figure 17.
Figure 17. Sampling sites at the Taipei International Airport (Lai et al., 2012). 29
In total, 672 integrated air samples were collected using a micro-orifice uniform deposition impactor (MOUDI) and a nano-MOUDI. Particle-bound PAHs (P-PAHs) were analyzed by gas chromatography with mass selective detector (GC/MSD). The five most abundant species of P-PAHs on all sampling days were naphthalene (NaP), phenanthrene (PA), fluoranthene (FL), acenaphthene (AcP), and pyrene (Pyr). Total P-PAHs concentrations were 152.21, 184.83, and 188.94 ng/m3 in summer, autumn, and winter, respectively. On average, the most abundant fractions of benzo[a]pyrene equivalent concentration (BaPeq) in different molecular weights were high-weight PAHs (79.29 %), followed by medium-weight PAHs (11.57 %) and low-weight PAHs (9.14 %). The mean BaPeq concentrations were 1.25 and 0.94 (ng/m3) in ultrafine particles ( LW-PAHs (Nisbet and LaGoy 1992); thus, HW-PAHs have 33
the highest carcinogenic potential. A large HW-PAHs fraction at the airport apron is worth of study due to their adverse health impacts. Additionally, mean BaPeq concentrations were 1.25 and 0.94 (ng/m3) in UFPs and nano-particles, respectively. Although no workplace exposure limits for PAHs exist in Taiwan, the percentage of total BaPeq in the ultrafine size range was approximately 70.15 %. Therefore, the study concluded that a possibility of long-term adverse health effects exists following chronic exposure by inhalation by personnel working at the airport apron. Table 5. Mean BaPeq concentrations (ng/m3) in different seasons at the apron of the Taipei International Airport (Lai et al., 2012).
Pitarque et al. (1999) used three different biomarkers: sister-chromatid exchanges (SCE), micronuclei (MN), and the Comet assay, to evaluate different kinds of genetic damage in peripheral blood lymphocytes from 34 male workers at Barcelona airport exposed to low levels of hydrocarbons and jet fuel derivatives. The control group consisted of 11 unexposed men. We also investigated the ras p21 protein levels in plasma, in order to evaluate whether the ras gene could serve as a suitable potential marker of carcinogenic pollution in occupationally exposed cohorts. SCE and MN analyses failed to detect any statistically significant increase in the airport workers when compared with the controls, and in fact, the frequency of binucleated cells with MN in the exposed group was significantly lower than that obtained in the control. However, slight but significant differences in the mean comet length and genetic damage index were observed between the exposed and control groups when using the Comet assay. There were no statistically significant differences between both groups in p21 plasma levels. Smoking was shown to affect significantly both SCE and high frequency cells HFC in the exposed group.
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Cavallo, et al. (2002) used the Comet assay to investigate DNA damage in flight personnel with the aim of assessing potential health hazards in this occupational category. The study included 40 civil air-crew members who had been flying long-haul routes for at least 5 years, and compared them with a homogeneous control group of 40 healthy male ground staff. The Comet assay, or single-cell gel electrophoresis (SCGE), detects DNA single- and doublestrand breaks (DSBs) and alkali-labile lesions in individual cells, and is a powerful and sensitive technique for detecting genetic damage induced by different genotoxic agents. Taking into consideration occupational risk and possible confounding factors, this assay showed a small increase that did not reach statistical significance, of DNA damage in longhaul crew members compared to controls, indicating a lack of evident genotoxic effects. An association, although again not statistically significant, was found between reduced DNA damage and use of protective drugs (antioxidants). Cavallo et al. (2006) carried out in 2005 a follow-up study with the aim to to characterize the exposure and to evaluate genotoxic and oxidative effects in airport personnel (n = 41) in comparison with a selected control group (n = 31). Environmental monitoring of exposure was carried out analysing 23 PAHs on air samples collected from airport apron, airport building and terminal/office area during 5 working days. The urinary 1-hydroxy-pyrene (1OHP) following 5 working days, was used as biomarker of exposure. Genotoxic effects and early direct-oxidative DNA damage were evaluated by micronucleus (MN) and Fpg-modified comet assay on lymphocytes and exfoliated buccal cells, and by chromosomal aberrations (CA) and sister chromatid exchange (SCE) analyses. For comet assay, tail moment (the product of comet relative tail intensity and length) values from Fpg-enzyme treated cells (TMenz) and from untreated cells (TM) were used as parameters of oxidative and direct DNA damage, respectively. The exposed group showed a higher mean value of SCE frequency in respect to controls (4.6 versus 3.8) and an increase (1.3-fold) of total structural CA in particular breaks (up to 2.0-fold) and fragments (0.32% versus 0.00%), whereas there were no differences of MN frequency in both cellular types. Comet assay evidenced in the exposed group a higher value in respect to controls of mean TM and TMenz in both exfoliated buccal cells (TM 118.87 versus 68.20, p = 0.001; TMenz 146.11 versus 78.32, p < 0.001) and lymphocytes (TM 43.01 versus 36.01, p = 0.136; TMenz 55.86 versus 43.98, p = 0.003). An oxidative DNA damage was found, for exfoliated buccal cells in the 9.7% and for lymphocytes in the 14.6% of exposed in respect to the absence in controls. According to the authors, the findings furnish a useful contribution to the characterization of civil airport
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exposure and suggest the use of comet assay on exfoliated buccal cells to assess the occupational exposure to mixtures of inhalable pollutants at low doses since these cells represent the target tissue for this exposure and are obtained by non-invasive procedure. The recent study by Cavallo et al. (2009) compares and re-analyzes the results of three biomonitoring studies performed on populations including airport workers, occupationally exposed to complex chemical mixtures, at low doses, to evaluate the suitability of different biomarkers of genotoxic effects. Among the considered groups of the study, the airport personnel, was found to have an increase of TM in lymphocytes, confirming an induction of early DNA damage in this cell type, which resulted from exposure to PAHs. The findings of this study, particularly the higher extent of DNA damage in airport personnel as compared with the pavers group, can be explained by the different composition and amounts of PAHs in the two mixtures, which were inhaled by the two categories of workers. Previous studies of the authors have shown that airport personnel were exposed to higher amounts of total PAHs (27.70 lg/ m3 in the airport apron area and 17.27 lg/m3 in terminal building area) than pavers (2.84 lg/m3 on paving site). In particular, a prevalence of 2–3 ring PAHs (27.69 lg/m3 in the airport apron area and 17.24 lg/m3 in the terminal building area) were characterized at airport sampling sites as compared with 2.69 lg/m3 at the paving site. In airport the PAHs present in highest amounts were the 2 ring- PAHs 1-methylnaphthalene, 2-methylnaphthalene, 2,6dimethylnaphthalene, acenaphthene, and naphthalene. The presence of DNA damage by the comet assay using lymphocytes, and particularly using the exfoliated buccal cells of exposed airport personnel, demonstrates the higher sensitivity of the comet assay as compared with the MN test, confirming the results of Pitarque et al. (1999) on the same category of workers. According to the study this demonstrates the suitability of using non-invasive exfoliated cells to detect early genotoxic effects of PAHs exposure. The study concludes that exfoliated buccal cells, obtained by a non-invasive procedure, represent suitable human cells to assess occupational exposure to inhalable complex mixture of genotoxic chemicals, at low doses. Moreover, the comet assay seems to be more suitable for the prompt evaluation of the genotoxic effects of PAHs mixtures containing volatile substances, whereas the MN test seems more appropriate to evaluate the effects of exposure to antineoplastic agents. Apart from the assessment of health effects in occupational settings, there are a number of studies assessing the health impacts of particulate aircraft emissions to the general population:
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•
Barrett et al. (2010) applied modelling methods to estimate global mortality attributable to aircraft cruise emissions.
•
Arunachalam et al. (2011) estimated the incremental contribution of commercial aviation emissions during landing and takeoff (LTO) cycles from three U.S. airports
The study by Barrett et al. (2010) considers in addition to landing and takeoff emissions, also aircraft cruise emissions, and suggests that impacts to human health extend over a hemispheric scale. On this basis, the study provides a first estimate of premature mortalities attributable to aircraft emissions globally. It estimates that
