Space Science for Healthy Cities

For a long time UK air pollution research focused on advancing our understanding of atmospheric processes and reactions. More recently attention has turned to the issue of air quality, particularly in urban centres, addressing important research questions around how our cities, and the activities we do in and around them, influence air quality and consequently our health. 

The STFC Air Quality Network (SAQN) aims to bring together research, industry and policy to tackle air quality challenges, using the capabilities of the Science and Technology Facilities Council (STFC). STFC has a broad range of facilities, ranging from cutting edge laser technology to sensor development for harsh environments via high performance computing, data analytics and modelling. Much of the technology has been developed for astrophysics research and space science, but scientists are increasingly finding applications for this research much closer to home.

SAQN has developed new collaborations between teams of air quality researchers and STFC scientists, providing seed funding for research ideas tackling air quality issues. In this article we will take a look at the projects that could help improve our understanding of air quality in cities.

Indoor air quality 

It is no surprise that we spend 90% of our time indoors (World Health Organisation), and attention is turning to the quality of the air we breathe in these spaces. One research tool at our disposal is computational fluid dynamics (CFD), which can simulate and visualise the spread of gases or particles in an enclosed space based on real world data. STFC’s Scientific Computing Department has applied their considerable expertise to the question of how human behaviour affects our air quality.

Using a unit designed to simulate a real-world kitchen environment (the DOMESTIC facility, then based at the University of Chester), the team examined the effects of cooking and cleaning on the air quality in the room, using a timetable of activities based on data in the UK Time Use Survey (UKTUS). They carried out the experiment using different levels of ventilation to see what effect this had. Measurements of biological particles, particulate matter (PM) and carbon dioxide (CO₂) were taken and used to improve numerical simulations of the air flow inside the chamber, leading to 3D visualisations of the flow of particles. The visualisation of the CO₂ flow (see Figure 1) clearly shows the source of the gas at the cooker and its movement around the space.

Comparing the real-world measurements with the simulation improves the accuracy of the computer modelling, making it more realistic. This can then be used to determine the best form of ventilation for existing or planned buildings without the need to take measurements from multiple sensors, taking account of real-world human behaviour.

“comparing the real-world measurements with the simulation improves the accuracy of the computer modelling, making it more realistic”

This pilot study found that modelling of the CO₂ levels was comparable to measured concentrations, but demonstrated the need for further work in modelling other pollutants such as particulate matter. These microscopic particles are associated with increased risk of multiple health impacts, including coronary heart disease and stroke. The SAQN have funded a further proof of concept study to develop the CFD model, specifically improving the accuracy of prediction for different PM sizes, and validating the model using the same DOMESTIC unit (now located at the University of York).

Dr Stefano Rolfo is leading this project and brings a wealth of knowledge from the STFC’s Scientific Computing Department. “STFC, via the Scientific Computing Department, has a long-standing experience in numerical modelling for High Performance Computing (HPC). The objective of this project is to use state of the art computational fluid dynamics modelling together with Lagrangian Particle Tracking to investigate particulate dispersion originated from indoor activities such as cooking or cleaning. This will show to the air quality community the potential of CFD and HPC together and how these can be used to progress research for indoor air quality and applied to test new solutions for indoor ventilation.”

Health impacts of air pollution 

Our cities pose risks to health as a result of the pollutant emissions from high volumes of traffic. Vehicles generate large amounts of PM from combustion engines, brake, tyre and road wear and dust resuspension. This pollutant has been linked to a wide variety of health impacts in recent years, affecting every organ of the body. One of the impacts is an increased risk of dementia, which affects around 50 million people worldwide, a number predicted to triple over the next 30 years. But the mechanism for particles to travel from the lungs to the brain is not yet fully understood.

STFC’s Central Laser Facility (CLF) is helping to visualise this issue. It is thought that particles may pass into the bloodstream in the lungs, and are then transported through blood vessels to the brain, where they can cross the blood-brain-barrier (BBB). To test this idea, Dr Chang Guo of the UK Health Security Agency (UKHSA) is examining the behaviour of particles in brain tissue samples. STFC’s Central Laser Facility will use focused ion beam scanning electron microscopy (FIB-SEM) to image the activity of individual particles to see how they behave in the tissues. Another STFC facility, the ISIS Neutron and Muon Source, will use neutron spectroscopy to see how the particles themselves change by examining them before and after their association with the BBB.

The outcome of this study can increase our understanding of how inhaled particles cause neurodegenerative disease, and could ultimately help us target the sources of particles that cause the most damage. Dr Andy Ward, Senior Scientist at STFC Central Laser Facility, said “Our super-resolution imaging microscopes in the CLF are routinely used for studying biological material. By combination with our laser manipulation techniques these microscopes now have the potential to become a new tool in air quality studies, where we can control the interaction between pollution particles and cellular surfaces. The CLF are keen to work with teams to investigate the current issues in air quality.”

Sensor networks for cities worldwide 

Tackling the problem of air pollution in cities requires accurate measurement of the problem. Which pollutants are present? What are the levels of each pollutant? Where are they emitted? Where do they go?

This presents a challenge in low-resource regions such as sub-Saharan Africa, where a lack of resources limits the number and quality of sensors available to measure the air quality. Low-cost sensors are needed, but without unduly compromising the accuracy of the measurements. Fortunately, STFC has created numerous instruments for use in atmospheric sensing, space science and satellite measurements, which require novel technologies that can work in harsh environments, need to be compact, lightweight, low power, autonomous… in short, all things that make them ideal for field deployment in air quality research.

Miniaturisation is the key to the DELTA-Mi project. A team from STFC, UK Centre for Ecology and Hydrology (UKCEH) and Coventry University are developing a next-generation sensor that can measure gases and aerosols, particularly focusing on ammonia (a precursor to particulate matter). Understanding chemical species composition is necessary to assess impacts on ecosystems and human health, and to inform actions that can mitigate poor air quality. DELTA-Mi will provide much-needed observation data on the reactive gas and aerosol phase components in a cost-effective, easy-to-operate, time-integrated atmospheric measurement at sufficient spatial and temporal scales. In the future, these sensing units could be seen across cities around the world, building up our picture of air quality where it is needed most.

“understanding chemical species composition is necessary to assess impacts on ecosystems and human health”

Overcoming the ‘measurement drift’ 

Another issue faced by cities in low-resource regions is a lack of calibration for low-cost sensors. Cities in sub-Saharan Africa make use of networks of low-cost sensors as a way to measure air quality, but generally without any high-performance measurements that can be used as a reference for calibration and control of data quality. Tiny variations over time in each sensor lead to major uncertainties in the overall picture. This ‘measurement drift’ makes it hard to gather meaningful data from the sensor network over a long period of time.

A portable reference unit that can provide reliable in situ calibration is being developed by a team from RAL Space, as part of a collaboration with Mirico, Coventry University, the University of Cambridge, and Enjoy the Air.

The Portable Reference Instrument for Air Measurements (PRIAM) will be a laser-based sensor performing open-path measurements. The sensor will use laser beams to detect atmospheric molecules over a beam path of ~100 m. The proof-of-concept instrument will demonstrate multi-species detection (CO₂ and methane to begin with) and the ability to scan the laser beam to detect over a range of directions. It is hoped that this will demonstrate drift-free atmospheric measurements in a field-deployable sensor.

Dr Thomas Wall from the RAL Space Spectroscopy Group said:

“This proof-of-concept project is a great opportunity to develop a new field-deployable sensor that has great potential to improve air quality measurements in low-resource regions. This project builds on RAL Space Spectroscopy Group expertise in developing instruments for environmental monitoring and atmospheric detection, using laser dispersion spectroscopy to make reliable, calibration-free measurements. Working with our developers we will develop an existing lab-based instrument into a field-deployable instrument, and will enhance the optical set-up to allow multi-species sensing. Our consortium also includes partners at Cambridge and Coventry Universities, and Enjoy the Air, who will build links with stakeholders around the world, particularly in sub-Saharan Africa and Australia. Through SAQN I have formed useful collaborations with universities and industry, allowing us to exploit and enhance STFC technologies.”

The STFC Air Quality Network (SAQN) 

Air pollution is a major, global issue classified in 2014 by the United Nations Environment Programme as the ‘world’s worst environmental health risk’. Costs to the UK from deaths attributable to air pollution are estimated at £20 billion per year but this is only part of the overall impact. Additional costs to the UK economy and society as a result of air pollution are associated with: increased morbidity creating pressure on the health service, reducing productivity and impacting quality of life; impacts on the natural environment including loss of biodiversity and reducing crop yields; and damage to built environments. There are therefore huge opportunities to deliver economic and societal impact from improving air quality.

The aim of the STFC Air Quality Network (SAQN) is to create a multidisciplinary community of experts, researchers, policy makers and businesses that can leverage Science and Technology Facilities Council (STFC) research, capabilities and facilities to address air quality challenges. The SAQN facilitates the exploitation of untapped potential of STFC capabilities to enhance and progress research into air pollution, particularly with relevance to impacts on human health and the environment. The network’s objectives are:

1. Building a broad multidisciplinary network of STFC scientists and air pollution stakeholders including those from the public and private sector as well as academia and research institutes.
2. Promoting the engagement of researchers with both industry and regulators/governments to drive mutual understanding and enable air pollution solutions development.
3. Increasing awareness of STFC facilities and capabilities within the air pollution community.
4. Initiating lasting collaborations to leverage funding for cutting-edge air pollution research.
5. Providing a forum to share information to ensure that researchers across the UK are aware of each other’s activities, building links and ensuring maximum benefit from investments.

The work of the SAQN cuts across all parts of the air quality system, including indoor and outdoor air pollution; activities that contribute to improving any aspect of that complex landscape with the involvement of STFC science, facilities or expertise can be supported.