Evaluation of the health impacts of aircraft nanoparticles using a surrogate soot source and in vitro cell exposure

Aircraft engines emit pollutants that degrade the air quality around airports, which may affect the health of local residents and employees at the airport. Specifically, nanoparticles emitted from gas turbine engines comprise soot aggregates, sulphur compounds, semi-volatile organic carbon and metallic ash. As the aircraft engine jet cools and mixes with the surrounding atmosphere, nucleation and condensation processes lead to a rapid growth in nucleation mode particles and condensation of semi-volatile compounds onto non-volatile soot aggregates. Aircraft nanoparticle emissions are characterised by their small size (<60 nm) relative to other combustion sources, e.g. road transport. They may therefore have particular health consequences that are currently under-studied and not well understood. Few studies have conducted in-vitro toxicology tests to evaluate the effects on human bronchial epithelial cells to exposure to aircraft soot emissions from aircraft engines. Much more work is needed to understand the different effects of aircraft nanoparticles and the role of their different properties and chemical constituents.

This project aims to contribute to the understanding of the health impacts pathways of nanoparticles by developing and experimental methodology to test cellular responses to different sized nanoparticles and chemical compositions. The specific objectives of the project are to:

1. Review the literature on aircraft nanoparticle emissions, nanoparticle measurements near airports, and health impacts of different types and sources of combustion aerosols, including cellular response studies.
2. Develop laboratory source of soot particles that can be used to generate a tuneable surrogate aircraft aerosol in terms of particle size distribution and morphology, chemical composition and different coatings, and atmospheric ageing and oxidation. The soot source will be based on a burner design that has been used as a surrogate for aircraft soot particles before, and additional features such as organic carbon coatings and atmospheric ageing will be developed.
3. Use the surrogate soot source to design and conduct a comprehensive matrix of experiments to evaluate cellular responses to particle size and morphology, chemical composition of coatings, and atmospheric ageing. For example, aerosol classifiers could separate particular particle sizes before deposition on the cell culture to control for the effects of particle size. Similarly, particles could be coated with different materials, or have their coating removed by the use of a catalytic stripper. These methods are already established and involve exposure of primary human lung cells to increasing concentrations of the particles and determination of cell viability (MTT/LDH/apoptosis assays), mediator production (ie pro-inflmmatory responses; ELISA assays), oxidative stress (ROS measurement), mitochondrial integrity (mitotracker), cellular antioxidant depletion (GSH oxidation) and particle uptake. Positive controls (eg ZnO nanoparticles) with known toxicity will be tested in parallel.
4. Evaluate potential health impacts of aircraft nanoparticle emissions around airports using existing evidence and new modelling works to understand how health risks may vary with distance from the airport, and other factors such as weather conditions.
Novel engineering/physical sciences content
Development of particle technology techniques to generate soot nanoparticles with different coatings, sizes, shapes
Health impacts of pollution from engineering systems, specifically aircraft engine emissions. This could inform development of air quality standards.

Research council themes
Relevant EPSRC themes: Engineering, Energy
Relevant EPRSC research areas: Analytical science, Built environment, Infrastructure and urban systems, Particle technology, Sensors and instrumentation

Aerosol science has a significant impact on a broad range of disciplines, extending from inhaled drug delivery, to combustion science and its health impacts, aerosol assisted routes to materials, climate change, and the delivery of agricultural and consumer products. Estimates of the global aerosol market size suggest it will reach $84 billion/year by 2024 with products in the personal care, household, automotive, food, paints and medical sectors. Air pollution leads to an estimated 30-40,000 premature deaths each year in the UK, and aerosols transmit human and animal infections. More than 12 million people in the UK live with lung disease such as asthma, and the NHS spends ~£5 billion/year on respiratory therapies. Many of the technological, societal and health challenges central to these areas rely on core skills and knowledge of aerosol science. Despite this, an Industrial Workshop and online survey (held in preparation for this bid) highlighted the current doctoral skills gap in aerosol science in the UK. Participating industries reported that only 15% of their employees working with aerosol science at doctoral-level having received any formal training. A CDT in aerosol science, CAS, will fill this skills gap, impacting on all areas of science where core training in aerosol science is crucial.

Impact on the UK aerosol community: Aerosol scientists work across governmental policy, industrial research and innovation, and in academia. Despite the considerable overlap in training needs for researchers working in these diverse sectors, current doctoral training in aerosol science is fragmentary and ad hoc (e.g. the annual Fundamentals of Aerosol Science course delivered by the Aerosol Society). In addition, training occurs within the context of individual disciplines, reinforcing artificial subject boundaries. CAS will bring coherence to training in the core physical and engineering science of aerosols, catalysing new synergies in research, and providing a focal point for training a multidisciplinary community of researchers. Working with the Aerosol Society, we will establish a legacy by providing training resources for future researchers through an online training portal.

Impact on industry and public-sector partners: 45 organisations have indicated they will act as CAS partners with interests in respiratory therapies, public health, materials manufacturing, consumer and agricultural products, instrumentation, emissions and environment. Establishing CAS will deliver researchers with the necessary skills to ensure the UK establishes and sustains a scientific and technical lead in their sectors. Further, it will provide an ideal mechanism for delivering Continuing Professional Development for the existing workforce practitioners. The activity of CAS is aligned to the Industrial Strategy Challenge Fund (e.g. through developing new healthcare technologies and new materials) and the EPSRC Prosperity Outcomes of a productive, healthy (e.g. novel treatments for respiratory disease) and resilient (e.g. adaptations to climate change, air quality) nation, with both the skilled researchers and their science naturally translating to long-lasting impact. Additionally, rigorous training in responsible innovation and ethical standards will lead to aerosol researchers able to contribute to developing: regulatory standards for medicines; policy on air quality and climate geoengineering; and regulations on manufactured nano-materials.

Public engagement: CAS will provide a focal point for engaging the public on topics in aerosol science that affect our daily lives (consumer products, materials) through to our health (inhalation therapeutics, disease transmission and impacts of pollution) and the future of our planet (geoengineering). Supported by a rigorous doctoral level training in aerosol science, this next generation of researchers will be ideally positioned to lead debates on all of these societal and technological challenges.