Risk factors of jet fuel combustion products

doi:10.1016/j.toxlet.2003.12.040

Toxicology Letters

Volume 149, Issues 1–3, 1 April 2004, Pages 295-300

https://doi.org/10.1016/j.toxlet.2003.12.040 Get rights and content

Abstract

Air travel is increasing and airports are being newly built or enlarged. Concern is rising about the exposure to toxic combustion products in the population living in the vicinity of large airports.

Jet fuels are well characterized regarding their physical and chemical properties. Health effects of fuel vapors and liquid fuel are described after occupational exposure and in animal studies. Rather less is known about combustion products of jet fuels and exposure to those.

Aircraft emissions vary with the engine type, the engine load and the fuel. Among jet aircrafts there are differences between civil and military jet engines and their fuels. Combustion of jet fuel results in CO₂, H₂O, CO, C, NO_x, particles and a great number of organic compounds. Among the emitted hydrocarbons (HCs), no compound (indicator) characteristic for jet engines could be detected so far. Jet engines do not seem to be a source of halogenated compounds or heavy metals. They contain, however, various toxicologically relevant compounds including carcinogenic substances. A comparison between organic compounds in the emissions of jet engines and diesel vehicle engines revealed no major differences in the composition. Risk factors of jet engine fuel exhaust can only be named in context of exposure data. Using available monitoring data, the possibilities and limitations for a risk assessment approach for the population living around large airports are presented. The analysis of such data shows that there is an impact on the air quality of the adjacent communities, but this impact does not result in levels higher than those in a typical urban environment.

Introduction

The increasing air travel worldwide leads to building of new airports and enlargement of existing airports. Concern is rising about the exposure to toxic combustion products of jet fuel in the population living in the vicinity of large airports.

Jet fuels are well characterized regarding their physical and chemical properties. Health effects of fuel vapors and of liquid fuel via skin contact are described after occupational exposure and in animal studies. Rather less is known about combustion products of jet fuels and exposure to those.

The present knowledge about possible health risk factor deriving from exposure to jet engine exhaust is described. Using available monitoring data, a risk assessment approach is demonstrated for the population living around large airports.

Section snippets

Aviation fuels

Jet engines are fuelled with kerosene, which is a complex mixture of hydrocarbons (HCs) with a boiling point range between 145 and 300 °C. Jet fuels are a similar petroleum fraction (middle distillation range) as heating oil and diesel fuel. The major aviation fuels are jet propulsion fuel 8 (JP-8) for military engines and Jet A1 for civil aviation engines. The properties of Jet A1 turbine fuel including specification of additive are defined in the Defence Standard DEF STAN 91-91/1 (1994). Some

Jet engine emissions

Aircraft emissions vary with the engine type, the engine load and the fuel. Among jet aircrafts, there are differences between civil and military jet engines and their fuels. The ICAO (1981) gives emission limits for turbine engines with a performance >26.7 kN. The regulated components are: hydrocarbons, nitrogen oxides (NO_x), carbon monoxide (CO) and smoke number (SN). The engine emissions are measured according to a defined test cycle, the landing and take off (LTO) cycle. This test cycle

Toxicology of jet engine emissions

Although the toxicology and carcinogenicity of some jet fuels as such has been evaluated (IARC, 1989a), comparable studies on jet engine emissions as they exist for Diesel and gasoline engine emissions (IARC, 1989b) are not yet available. Health effect after occupational exposure to jet engine emissions—like eye and respiratory irritations due to aldehydes—have been described (Miyamato, 1986, Kobayashi and Kikukawa, 2000, Tunnicliffe et al., 1999). A study on cancer incidence in occupationally

Exposure to jet fuel combustion products around airports

Since no indicator or characteristic compound for jet engine emissions has been found, monitoring ambient air concentrations is the only approach to measure at least for non occupationally human exposure. Monitoring data of air pollutants are available for many airports, but they are mostly restricted to classical pollutants like sulfur dioxide, nitrogen oxides, carbon monoxide and particles and a few others in special monitoring programs. Table 6 summarizes such data for the German airports of

Conclusions

Available data on jet engine fuels and their combustion products reveal no specific toxic compound that can be used as a marker or indicator for exposure. Higher alkanes may be an indicator for occupationally exposed persons. For a population living in the vicinity of a large airport, risk assessment can only be achieved by relying on air monitoring data. Such data show that there is an impact on the air quality of the adjacent communities, but that impact does not result in levels higher than

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Aircraft emissions contribute to overall ambient air pollution, including ultrafine particle (UFP) concentrations. However, accurately ascertaining aviation contributions to UFP is challenging due to high spatiotemporal variability along with intermittent aviation emissions. The objective of this study was to evaluate the impact of arrival aircraft on particle number concentration (PNC), a proxy for UFP, across six study sites 3–17 km from a major arrival aircraft flight path into Boston Logan International Airport by utilizing real-time aircraft activity and meteorological data. Ambient PNC at all monitoring sites was similar at the median but had greater variation at the 95th and 99th percentiles with more than two-fold increases in PNC observed at sites closer to the airport. PNC was elevated during the hours with high aircraft activity with sites closest to the airport exhibiting stronger signals when downwind from the airport. Regression models indicated that the number of arrival aircraft per hour was associated with measured PNC at all six sites, with a maximum contribution of 50% of total PNC at a monitor 3 km from the airport during hours with arrival activity on the flight path of interest (26% across all hours). Our findings suggest strong but intermittent contributions from arrival aircraft to ambient PNC in communities near airports.
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Moreover, little is known about aviation-related UFP exposure, as most studies focus on road-traffic-related UFP (Ohlwein et al., 2019). UFP levels have been shown to be elevated around large airports (Hudda et al., 2018, 2014; Keuken et al., 2015), reaching similar levels as urbanised areas (Tesseraux, 2004), with different sources influencing UFP composition and size. Aviation-related UFP tend to be smaller (mainly 10–20 nm (Keuken et al., 2015; Mazaheri et al., 2013; Stacey, 2019)) than those from road traffic (mainly > 50 nm (Harrison et al., 2011; Liu et al., 2015; Ntziachristos et al., 2007)), although an overlap in size range exists, especially in the 20–30 nm range (Voogt et al., 2019).
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We investigated health effects of controlled short-term human exposure to UFP near a major airport.
In this study, 21 healthy non-smoking volunteers (age range: 18–35 years) were repeatedly (2–5 visits) exposed for 5 h to ambient air near Schiphol Airport, while performing intermittent moderate exercise (i.e. cycling). Pre- to post-exposure changes in cardiopulmonary outcomes (spirometry, forced exhaled nitric oxide, electrocardiography and blood pressure) were assessed and related to total- and size-specific particle number concentrations (PNC), using linear mixed effect models.
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Short-term exposures to aviation-related UFP near a major airport, was associated with decreased lung function (mainly FVC) and a prolonged QTc interval in healthy volunteers. The effects were relatively small, however, they appeared after single exposures of 5 h in young healthy adults. As this study cannot make any inferences about long-term health impacts, appropriate studies investigating potential health effects of long-term exposure to airport-related UFP, are urgently needed.
VOC tracers from aircraft activities at Beirut Rafic Hariri International Airport
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The above studies provide a significant insight into VOC (mainly non-methane hydrocarbon (NMHC)) speciation from aircraft exhaust. However, no special jet exhaust VOC was identified as tracer (Schürmann et al., 2007; Tesseraux, 2004). The identification of aircraft tracers is essential for the assessment of the impact of the airport activities on air quality.
This is the first study to assess the speciation of 48 VOCs from around 100 commercial aircraft under real operation, as close as possible to aircraft engines during the various modes of the landing/takeoff (LTO) cycles to identify special aircraft fingerprints and markers. Also, Jet A-1 kerosene vapor, gasoline exhaust, and the ambient airport concentrations were assessed. Air samples were taken at Beirut Rafic Hariri International Airport inside adsorbent tubes using a portable automatic remote sampler and analyzed using gas chromatographic techniques (GC-MS and GC-FID). Results showed that heavy alkanes (C₈-C_14, mainly n-nonane and n-decane), which contributed to about 51–64% of the total mass of heavy VOCs emitted by aircraft, and heavy aldehydes (nonanal and decanal) – although to a lesser amount – can be considered as potential tracers for aircraft emissions due to both their exclusive presence in aircraft-related emissions and their absence from gasoline exhaust emissions. On the other hand, the total concentration of heavy alkanes in the airport's ambient air was 47% of the total mass of heavy VOCs measured. No aircraft tracer was identified among the light VOCs (≤C₇); however, results showed that emissions of light VOCs decrease as the engine power increases. Also, auxiliary power unit (APU) emissions were identified to be of the same order of magnitude as main engine emissions. This study opens the door for future studies aiming at evaluating the impact of airport activities on air quality and human health within or away from the airport vicinity.
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The results of air quality monitoring carried out over several years (2008–2012) in two international airports near Rome (labelled as A and B) are reported and discussed. Airport A serves regular flights, airport B operates low-cost flights and, during the period investigated, had about 17% of airport A aircraft traffic load.
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Air quality degradation in the locality of airports is considered by some to pose a real public health hazard (Barrett et al., 2013) and some recent estimates of the aviation contribution to premature mortality have been reported (e.g., Ratliff et al., 2009; Levy et al., 2012; Ashok et al., 2013; Yim et al., 2013). Although at the current time, no specific target toxic compound has been identified to be used as a marker or indicator for human exposure to jet engine fuels and their combustion products (Tesseraux, 2004), it has been estimated that over 2 million civilian and military personnel per year are occupationally exposed to jet fuels and exhaust gases (Pleil et al., 2000; Ritchie, 2003; Cavallo et al., 2006). Kerosene-based fuels have the potential to cause acute or persistent neurotoxic effects from acute, sub-chronic, or chronic exposure of humans or animals (Ritchie et al., 2001), although evidence is lacking that current levels of exposure are harmful.
Civil aviation is fast-growing (about +5% every year), mainly driven by the developing economies and globalisation. Its impact on the environment is heavily debated, particularly in relation to climate forcing attributed to emissions at cruising altitudes and the noise and the deterioration of air quality at ground-level due to airport operations. This latter environmental issue is of particular interest to the scientific community and policymakers, especially in relation to the breach of limit and target values for many air pollutants, mainly nitrogen oxides and particulate matter, near the busiest airports and the resulting consequences for public health. Despite the increased attention given to aircraft emissions at ground-level and air pollution in the vicinity of airports, many research gaps remain. Sources relevant to air quality include not only engine exhaust and non-exhaust emissions from aircraft, but also emissions from the units providing power to the aircraft on the ground, the traffic due to the airport ground service, maintenance work, heating facilities, fugitive vapours from refuelling operations, kitchens and restaurants for passengers and operators, intermodal transportation systems, and road traffic for transporting people and goods in and out to the airport. Many of these sources have received inadequate attention, despite their high potential for impact on air quality. This review aims to summarise the state-of-the-art research on aircraft and airport emissions and attempts to synthesise the results of studies that have addressed this issue. It also aims to describe the key characteristics of pollution, the impacts upon global and local air quality and to address the future potential of research by highlighting research needs.

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^☆: Parts of this presentation have been published before: Tesseraux et al., 1998.

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Risk factors of jet fuel combustion products☆