Aerosols are everywhere in the atmosphere, ranging in size from the very small nanometre-sized particles produced by cars through to larger water droplets in clouds with diameters similar to that of a human hair. Not only can pollution particles lead to increased rates of morbidity and mortality, but they can also act as a means of transporting bacteria and viruses, facilitating disease transmission. Indeed, infectious diseases are spread by the airborne route through aerosol droplets produced by the human body and expelled through coughing and sneezing. Such events account for some of the deadliest infectious diseases, including tuberculosis (TB), severe acute respiratory syndrome (SARS) and bacterial meningitis, all of which have a major impact on our society. Despite the significant health and financial burdens that arise from the airborne transmission of pathogens, studying bacteria and viruses in the aerosol phase remains challenging as few measurement techniques exist to explore the changes in viability and infectivity that may occur during airborne transport. In the proposed research, we will develop a novel instrument for exploring the processes that affect how well bacteria survive when in airborne droplets. In particular, we will build and test an instrument that will allow the suspension and manipulation of aerosol particles in air containing a known number of bacteria. For example, we will develop an approach to generate individual droplets that mimic our coughs and sneezes, each containing a known number of bacteria. By subtly manipulating each droplet, we will be able to catch and levitate them in an electric field for any amount of time. We will then, in a controlled way, deposit the droplets into a dish containing suitable conditions to allow any bacteria present to grow. Whilst airborne, we will be able to change the temperature and humidity of the environment experienced by the droplets. We will also expose them to light (similar to sunlight) and also to typical atmospheric chemicals like ozone. Combined, these capabilities will allow us to simulate the processes the bacteria experience whilst moving from person-to-person. Thus, we will be able to measure how different environmental conditions influence how many bacteria remain alive at different time points. Once the instrument has been built and tested, we will study a bacterium (Neisseria meningitidis also known as meningococci) which causes blood and brain infections but can be spread from person to person by coughing and sneezing. We will measure the airborne survival of meningococci at different times, temperatures and humidities, with conditions representative of cold-wet or cold-dry environments to simulate winter day conditions typical of the UK, or hot-dry conditions typical of the Africa dry season. These conditions represent seasons when the disease rates are highest in both regions. Finally, we will combine droplet capture with an exciting new instrument, the NanoString, which can measure how bacteria change in ways which could make them more or less able to cause disease. Together, the capabilities to measure not only how long bacteria survive but how they change outside of our bodies will help us to use mathematics to better model risks of disease spread, and also to identify novel better means of preventing person-to-person infection by aerosol (airborne) transmission.

Aerosol science, the study of airborne particles from the nanometre to the millimetre scale, has been increasingly in the public consciousness in recent years, particularly due to the role played by aerosols in the transmission of COVID-19. Vaccines and medications for treating lung and systemic diseases can be delivered by aerosol inhalation, and aerosols are widely used in agricultural and consumer products. Aerosols are a key mediator of poor air quality and respiratory and cardiac health outcomes. Improving human health depends on insights from aerosol science on emission sources and transport, supported by standardised metrology. Similar challenges exist for understanding climate, with aerosol radiative forcing remaining uncertain. Furthermore, aerosol routes to the engineering and manufacture of new materials can provide greener, more sustainable alternatives to conventional approaches and offer routes to new high-performance materials that can sequester carbon dioxide. The physical science underpinning the diverse areas in which aerosols play a role is rarely taught at undergraduate level and the training of postgraduate research students (PGRs) has been fragmentary. This is a consequence of the challenges of fostering the intellectual agility demanded of a multidisciplinary subject in the context of any single academic discipline. To begin to address these challenges, we established the EPSRC Centre for Doctoral Training in Aerosol Science in 2019 (CDT2019). CDT2019 has trained 92 PGRs with 40% undertaking industry co-funded research projects, leveraged £7.9M from partners and universities based on an EPSRC investment of £6.9M, and broadened access to our unique training environment to over 400 partner employees and aligned students. CDT2019 revealed strong industrial and governmental demand for researchers in aerosol science. Our vision for CDT2024 is to deliver a CDT that 'meets user needs' and expands the reach and impact of our training and research in the cross-cutting EPSRC theme of Physical and Mathematical Sciences, specifically in areas where aerosol science is key. The Centre brings together an academic team from the Universities of Bristol (the hub), Bath, Birmingham, Cambridge, Hertfordshire, Manchester, Surrey and Imperial College London spanning science, engineering, medical, and health faculties. We will assemble a multidisciplinary team of supervisors with expertise in chemistry, physics, chemical and mechanical engineering, life and medical sciences, and environmental sciences, providing the broad perspective necessary to equip PGRs to address the challenges in aerosol science that fall at the boundaries between these disciplines. To meet user needs, we will devise and adopt an innovative Open CDT model. We will build on our collaboration of institutions and 80 industrial, public and third sector partners, working with affiliated academics and learned societies to widen global access to our training and catalyse transformative research, establishing the CDT as the leading global centre for excellence in aerosol science. Broadly, we will: (1) Train over 90 PGRs in the physical science of aerosols equipping 5 cohorts of graduates with the professional agility to tackle the technical challenges our partners are addressing; (2) Provide opportunities for Continuing Professional Development for partner employees, including a PhD by work-based, part-time study; (3) Deliver research for end-users through partner-funded PhDs with collaborating academics, accelerating knowledge exchange through PGR placements in partner workplaces; (4) Support the growth of an international network of partners working in aerosol science through focus meetings, conferences and training. Partners and academics will work together to deliver training to our cohorts, including in the areas of responsible innovation, entrepreneurship, policy, regulation, environmental sustainability and equality, diversity and inclusion.

An aerosol consists of solid particles or liquid droplets dispersed in a gas phase with sizes spanning from clusters of molecules (nanometres) to rain droplets (millimetres). Aerosol science is a term used to describe our understanding of the collective underlying physical science governing the properties and transformation of aerosols in a broad range of contexts, extending from drug delivery to the lungs to disease transmission, combustion and energy generation, materials processing, environmental science, and the delivery of agricultural and consumer products. Despite the commonality in the physical science core to all of these sectors, doctoral training in aerosol science has been focussed in specific contexts such as inhalation, the environment and materials. Representatives from these diverse sectors have reported that over 90% of their organisations experience difficulty in recruiting to research and technical roles requiring core expertise in aerosol science. Many of these will act as CDT partners and have co-created this bid. We will establish a CDT in Aerosol Science that, for the first time on a global stage, will provide foundational and comprehensive training for doctoral scientists in the core physical science. Not only will this bring coherence to training in aerosol science in the UK, but it will catalyse new collaborations between researchers in different disciplines. Inverting the existing training paradigm will ensure that practitioners of the future have the technical agility and confidence to move between different application contexts, leading to exciting and innovative approaches to address the technological, societal and health challenges in aerosol science. We will assemble a multidisciplinary team of supervisors from the Universities of Bristol, Bath, Cambridge, Hertfordshire, Imperial, Leeds and Manchester, with expertise spanning chemistry, physics, biological sciences, chemical and mechanical engineering, life and medical sciences, pharmacy and pharmacology, and earth and environmental sciences. Such breadth is crucial to provide the broad perspective on aerosol science central to developing researchers able to address the challenges that fall at the boundaries between these disciplines. We will engage with partners from across the industrial, governmental and public sectors, and with the Aerosol Society of the UK and Ireland, to deliver a legacy of training packages and an online training portal for future practitioners. With partners, we have defined the key research competencies in aerosol science necessary for their employees. Partners will provide support through skills-training placements, co-sponsored studentships, and contribution to taught elements. 5 cohorts of 16 doctoral students will follow a period of intensive training in the core concepts of aerosol science with training placements in complementary application areas and with partners. In subsequent years we will continue to build the activity of the cohort through summer schools, workshops and conferences hosted by the Aerosol Society, virtual training and enhanced training activities, and student-led initiatives. The students will acquire a perspective of aerosol science that stretches beyond the artificial boundaries of traditional disciplines, seeing the commonalities in core physical science. A cohort-based approach will provide a national focal point for training, acting as a catalyst to assemble a multi-disciplinary team with the breadth of research activity to provide opportunities for students to undertake research in complementary areas of aerosol science, and a mechanism for delivering the broad academic ingredients necessary for core training in aerosol science. A network of highly-skilled doctoral practitioners in aerosol science will result, capable of addressing the biggest problems and ethical dilemmas of our age, such as healthy ageing, sustainable and safe consumer products, and climate geoengineering.