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Airliner Decontamination for Infection Control – Transition to the European Engineering, Regulatory and Operational Context

Final Report Summary - AIRCRAFT DECON. (Airliner Decontamination for Infection Control – Transition to the European Engineering, Regulatory and Operational Context)

The modern civil aviation system provides unprecedented opportunities for the rapid and efficient spread of infectious disease. There are significant ongoing concerns over routine air travel; however, these concerns are vastly magnified in the event of an epidemic/pandemic because: a) air travel transports infected individuals to new locations; b) aerosol person to person transmission can occur within the cabin and c) transmission can occur via cabin surfaces. In all three cases, efficient infection control strategies are needed, ranging from e.g. quarantine activities for 'a' to decontamination/sanitisation/cleaning activities for 'c'. The latter forms the background for this research project. The relative importance of these routes depends on the pathogen. E.g. in the case of noroviruses, surface contamination is particularly important. Norovirus infections are frequent on board cruise ships. It has been suggested that norovirus outbreaks on aircraft are extensively underreported, because passengers disperse at the end of the flight. Worryingly, influenza has been shown to have significant longevity on cabin materials. Simultaneously, there are ongoing concerns over the use of chemical and biological (chem.–bio.) agents by terrorists against aircraft. Airliners have long been a favoured terrorist target and the United States (US) anthrax attacks, plus the use of Sarin on the Tokyo subway system are worrying. Decontamination is an integral part of any chem.–bio - response (at a minimum aircraft must be decontaminated before flying them out from an airport for dismantling). A means of cleaning/sanitising/decontaminating aircraft cabins is therefore required. This must be both efficacious as an antimicrobial for the pathogen(s) of concern and safe to deploy in the context of flight/safety critical aircraft materials and systems.

This project focused on technologies for airliner decontamination that are relevant to the European context. The proposed project built on, but did not duplicate, a team-based cross-disciplinary activity led by the researcher in the USA, which was aimed at developing and demonstrating at full-scale, an airliner decontamination process for wide-body (i.e. twin aisle cabin) and narrow-body (single aisle) aircraft. The only known successful demonstrations of decontamination of an entire airliner cabin by chemical methods.

The overall goal of the proposed work was to transition these activities to the European context. Hence the objectives of the overall project were:
- Work conducted in the USA was on aircraft produced by US-based airframers and hence a determination is needed of whether the significant differences in the design, materials and construction of European built aircraft have implications for the safety of decontamination.
- The European regulatory climate with respect to aviation, environmental impact, metrics of antimicrobial efficacy, health and safety etc. is considerably different from that in the USA. Furthermore, in Europe there is (to some extent) a patchwork of national policies. Hence, the extent to which the process, as deployed in the USA, is compatible with European requirements needs to be determined.
- The impact of differences between USA and European airliner operations on the suitability of the decontamination process needs to be ascertained.
- As necessary, the design of the decontamination/sanitisation process will be modified for compatibility with operation in Europe.

The work carried out during the project included three aspects: comparison of features of air transport operations between European Union (EU) and USA and their impact on aircraft decontamination, comparison on the materials used in the aircraft fuselage and interiors for the European versus US produced aircraft and implications for decontamination and environmental impact of airline decontamination, which ultimately proved a key issue.

The work on the first aspect gathered, analysed and collated the information and data on the features of air transport operation in the and USA, which enabled the determination of the possible influences of air transport pattern on aircraft decontamination operation between the EU and USA. A report entitled 'airliner decontamination in the European context report one – comparison of European air transport with the USA' was compiled. The report analysed the data of 2007 and 2008 in terms of total air traffic passenger numbers, intra-EU (or domestic for the US) and extra-EU international air passenger numbers, seasonal and monthly variations of passenger numbers, air transport at airports, the number of flights, routes and fleet composition including aircraft type and age. This served as a basis for considering operational impact on decontaminations of the transition from the US to Europe.

The second aspect of work investigated the materials used in Airbus and Boeing airplanes. A report: 'Airliner decontamination in the European context report two –Materials for aircraft and its interiors for airbus and boeing airplanes' has been completed. The report collected and collated the information on the materials deployed in the aircraft fuselage and interiors for the airbus versus boeing airplanes, which would then enable to look into implications and potential impact of different airplane design and configuration on aircraft decontamination. This is particularly significant for EU as airbus has seen a return of aluminium-lithium alloys due to the development of the third generation of Al-Li alloys. The work served as a basis for considering whether changes to the engineering evaluation of decontamination performed by the PI in the US needs to be re-evaluated, extended or even duplicated for European built airframes.

Neither operations nor differences in materials were found to be key issues. Instead, attention was focussed heavily on a third aspect of work, which assessed the possible impact, particularly environmental, of aircraft decontamination operations. The work evaluated the fate of hydrogen peroxide in the case of normal release to atmosphere after operation or an accidental leak. A technical paper has been presented and published at the third international air transport and operations symposium (ATOS 2012) held in Delft university of technique in Netherland with a title of 'analysis of removal and decomposition pathways of vaporised hydrogen peroxide (VHP) for aircraft decontamination operation'. Followed on from this conference paper, a research paper has been submitted to the aeronautical journal with a title of 'impact assessment of aircraft decontamination by vapour phase hydrogen peroxide (VPHP)-removal and decomposition pathways of H2O2 and interaction with pollutants'. The work showed that the uptake to water droplets in the air, as a physical pathway, appears to be a major pathway for the removal of hydrogen peroxide vapour. The removal efficacy of hydrogen peroxide by water droplets is increased as the ambient temperature and humidity increases. The reaction between SO2 and hydrogen peroxide is relatively fast and could be with a scale of less than 10 minutes. SO2 has potential to become one of the major sinkers for VPHP. However, the amount of hydrogen peroxide consumed by SO2 will be determined by SO2 concentrations in surroundings. Along with the theoretical research, experimental researches to measure airport pollutant concentrations (Newcastle airport) and engine emissions have been carried out, which focused on measuring SO2 concentrations so as to be able to quantify the interactions between hydrogen peroxide and SO2.

The findings of the project have a direct impact on civil aviation authorities, airport and airline operators and national governments to enable them to make decisions based on scientific knowledge of readiness of aircraft decontamination technology and operations and its environmental impact in the case of epidemic or terrorist attacks. No fundamental barriers for the transition of airline decontamination from the USA to the EU have been identified.