Supporting the aims of Clean Air Day today, 20th June 2019, the Guardian has published a short film demonstrating the changing levels of pollution that children are exposed to as they walk to school in London. The film can be viewed here.
The Guardian Cities team worked closely with their colleagues in multimedia to create a film showing real-time air quality data as a mother takes her young children to school in north London. The video features mother-of-two Natasa pushing a pram and walking her daughter along Marylebone Road, with a Particles Plus instrument attached to the pram and an AQMesh pod on her daughter’s backpack.
The most important air quality parameters are displayed on-screen during the walk, with data including PM10, PM2.5 and nitrogen dioxide (NO2). The film producers have cleverly integrated the European yearly mean limits for these parameters into the display, with readings changing from blue to red when they exceed the limit, (which for PM10 and NO2 was most of the time!).
Documentary producer Anetta Jones, said: “Air quality is a vitally important issue for the health and wellbeing of city dwellers, but the main pollution threats are invisible, so we hope that initiatives such as this will help residents and visitors to better understand the threat that they face.”
The monitoring equipment was supplied by Air Monitors Limited. Their David Green said: “We have recently installed large numbers of AQMesh pods all over London as part of the Breathe London project, and data from these pods will be displayed on the project website. However, video is an enormously popular medium, and it is really exciting to see what can be achieved when the latest technologies in multimedia and air quality monitoring combine.”
A new network of air pollution monitors has been installed to record emissions from cruise ships docking in Greenwich.
The £80,000 network has been funded by the Port of London Authority (PLA) and installed in partnership with Breathe London and the borough councils covering both Greenwich and Tower Hamlets.
The eight monitoring stations, all located close to the Greenwich Ship Tier landing stage, will capture data around the clock with the raw data available via the websites of both the PLA and Breathe London. A full analysis of the results will be published in early 2020.
The monitors have been supplied by Gloucestershire-based Air Monitors Limited.
Robin Mortimer, PLA chief executive said: ‘The data these monitors collect will give us a comprehensive understanding of the impact that the cruise ships have on air quality when they are in town.
‘It’s crucial to have this information so that we can address the concerns that we know are very strongly held by local residents.’
The monitors are part of the PLA’s Air Quality Strategy, published in May 2018, the first to be produced by a UK port. It includes 25-year targets to halve levels of Nitrogen Oxides and Particular Matter from river-related sources, whilst growing use of the river for carrying both freight and passengers.
Measures already implemented include a programme of retrofitting older vessels with the latest environmentally-friendly technology.
In January, the Department for Transport (DfT) published the first-ever maritime strategy, which details their vision of a zero-emission shipping industry by 2050.
In it, the government said they are considering introducing targets to drive down emissions of GHGs and other air pollutants from UK shipping as ‘the volume of global trade increases.’
They also say they hope to have a group of hydrogen or ammonia powered domestic vessels in operation and at least one major ‘smart port’ in the UK to have all ship-side activity zero emission (including non-road mobile machinery like cranes).
Few people know how clean the air is where they live, work, exercise or where their children go to school. Although air quality can be shown to vary significantly over short distances, air pollution is generally measured using a small number of large, expensive and high quality monitoring stations. The equipment used in these stations is very accurate and complies with measurement standards but they are expensive to buy and maintain, as well as difficult to position because of their size and infrastructure requirements.
With most cities having a single figure number of reference stations at best, many neighbourhoods do not have access to regular and localised air quality information. Historically, the best solution currently is to fill the gaps through modelling, which combines available air quality readings with other information such as emissions inventory.
Demand from communities for better local air quality information is coming at a time when development of smaller, cheaper air quality sensors can provide a solution to the challenge. ‘Small sensor’ air quality systems can provide highly localised pollution measurements, including nitrogen dioxide (NO2) and the key particulate matter measurement, PM2.5, but to provide meaningful measurements on which communities and authorities can make decisions, the information must show traceability to reference measurements.
Many initiatives around the world are aiming to show what can be done, with one of the most ambitious being the Breathe London project in London. 100 small sensor systems are being used, in combination with data from London’s reference network, modelling and readings taken by Google cars modified to carry high quality air monitoring equipment. This project aims to demonstrate how such a ‘hyper-local’ network can be managed, creating a template which can be rolled out to other cities worldwide.
Similarly, 50 AQMesh small sensor air quality monitoring units have been installed to monitor air quality in each of the 50 zip codes in Minneapolis – Saint Paul, USA. “This project is about understanding small-scale differences in air pollution in urban areas in order to minimise exposure to harmful air pollutants, particularly for vulnerable communities. The Assessing Urban Air Quality project will use new air monitoring sensors to broaden our knowledge about air quality in Minneapolis and St. Paul”, commented Monika Vadali, Ph.D, who is leading the project.
AQMesh has also been used to monitor air quality around industrial sites and next to nearby communities which may be affected. As the monitoring units can be positioned with a high degree of flexibility, such as mounting on a lamp post, it is possible to capture data at exactly the point required. With measurements usually every 15 minutes, combined with local wind speed and direction information, it is possible to build up a highly localised picture of likely pollution exposure and identification of pollution sources.
Whilst regulatory authorities are currently defining testing methodologies to help users choose small sensor air quality systems, the best small sensor systems provide a useful and practical tool to supplement existing monitoring networks and are in active use around the world, providing new information about local air quality for a range of applications.
In an inter-connected world, air quality is increasingly becoming another measurement made available to the public, but how reliable is the data?
Common air pollutants such as NO2 and PM2.5 mix at different rates depending on their source and local weather conditions, particularly wind speed, leaving large local variations in pollution levels. Urban air quality has traditionally been managed by authorities using a combination of large, compliance standard (reference) measurement stations and modelling based on an emissions inventory. Research has shown that increasing the number of measurement points improves the spatial resolution of urban air quality models.
Small-sensor air quality monitoring technology offers the possibility of more local measurements, and its emergence coincides with the appetite from Internet of Things (IoT) developers to map air quality across cities in real-time and communicate this information to the city inhabitants in various ways. This is leading to a growing number of smart city projects using a range of monitoring devices, but understanding the air quality information gathered and sharing it with the public can still be complicated.
Many air quality sensors that are small, cheap and have low power consumption are often very limited by the influence of fluctuating temperatures and cross-gas effects and do not produce good air quality readings. It is therefore beneficial to use a small-sensor air quality monitoring system that incorporates processing, correction and a QA/QC process in order to offer meaningful readings. Environmental authorities, including the US EPA, have developed air quality indices (AQI) and other tools to communicate local air quality to the public. These authorities are looking at how to modify that approach to provide more localised information from small sensor-sensor systems, such as air quality in a neighbourhood – or even a street – rather than a whole section of a city.
AQMesh, a small-sensor air quality monitoring system, is being used in a variety of successful smart city projects which have a range of objectives, but with a common goal of informing the public about the air quality and pollution levels in the local area where they live and work.
‘Breathe London’ was launched in February, with a sophisticated network of air quality monitors to help investigate and improve London’s toxic air. A range of fixed and mobile sensors will be used to build up a real-time, hyperlocal image of London’s air quality. The technology company Air Monitors designed and installed the network of AQMesh air quality monitoring pods, as well as the air quality analysers that were specially adapted to operate inside Google Street View cars.
In Minneapolis, Minnesota Pollution Control Agency (MPCA) has deployed 50 AQMesh pods across 50 zip code areas in order improve understanding of the small-scale differences in air pollution within urban areas.
Similarly in Newcastle, 55 AQMesh pods, supplied and supported by Air Monitors, form part of a network of over 600 sensors managed by the UK’s first Urban Observatory, which aims to provide Newcastle’s citizens with a digital view of how cities work.
These smart cities demonstrate that meaningful and reliable air quality information can be shared with the public when networks are deployed effectively and supported by air quality professionals who understand the capabilities – and limitations – of small-sensor technology and how the local environment affects air quality readings.
The UK’s first Urban Observatory, led by Newcastle University, has been designed to provide a digital view of how cities work. AQMesh air quality monitoring equipment is being deployed across Newcastle and Gateshead in conjunction with other instruments for monitoring parameters such as air and water quality, noise, weather, energy use, traffic and even tweets.
Forming part of a network of over 600 sensors, the Urban Observatory has already collected over half a billion data points and the information is now starting to shed light on the way different systems interact across the city and provide a baseline against which future cities can be developed and managed.
To date Air Monitors, UK AQMesh distributor, has supplied 55 AQMesh pods and 6 conventional air quality monitoring stations. The conventional stations employ standard reference method instruments to measure key air quality parameters such as Nitrogen Dioxide, Ozone, Carbon Monoxide and Particulates. The AQMesh pods monitor similar parameters, but are smaller, solar-powered, wireless, web-enabled devices that can be quickly and easily located in almost any location.
Commenting on Air Monitors’ involvement in the Urban Observatory project, Managing Director Jim Mills says: “The conventional stations are delivering precise, accurate data, and the AQMesh pods are providing the portability and flexibility to monitor air quality accurately and reliably in the locations of greatest interest.”
“Perhaps the most interesting aspect of this project is its ability to engage with the community, providing detailed local air quality data so that both authorities and citizens can make informed decisions on how to reduce exposure to air pollution. Looking forward, it is clear that work in Newcastle will serve as a model for other cities around the world to follow.”
The National Observatories facility was established in 2017 with the Newcastle Urban Observatory as the founding member, supported by £8.5 million investment from EPSRC (Engineering and Physical Sciences Research Council). The guiding principles are to be technology agnostic and vendor non-exclusive, open by default and transparent by design whilst developing a valued, long-term, sustainable platform. In order for the data to be useful to better understand cities and to facilitate evidence based decision-making across a range of scales and sectors, the data needs to be robust and reliable with known data quality that can be validated.
The AQMesh pods are also being used as part of the ‘Sense My Street’ tool box which enables local communities to deploy sensors and locate them on the streets, collecting evidence to inform or even change their communities.
Phil James, who co-leads the Urban Observatory research, explains: “Cities are complex environments and if we want to develop them sustainably we have to understand how everything interacts.
“By compiling observations and comparing the data, for the first time we are now able to make more informed decisions about designing our cities to work better for people and the environment. Through the Sense my Street project, we are able to give communities the power to gather data relevant to issues that are important to them at a very local scale.”
All of the data is freely available at Newcastle University’s website: www.urbanobservatory.ac.uk, and is being used by researchers, local authorities, regulators, developers, town planners, businesses and members of the public.
AQMesh has been measuring ozone (O3) using small sensors since 2011 and the readings from the latest generation electrochemical sensor, using AQMesh v4.2.3 processing, as compared to co-located certified reference readings, consistently show an R2 of over 0.9 with an accuracy ±10ppb (20µg/m3).
AQMesh pods have been measuring ozone levels around the world and co-location comparison studies show very good performance against reference equipment from the latest sensor and processing version. Ozone levels have been particularly high across Western Europe over this summer but are a regular concern in many parts of the world, including the USA. However, there are huge gaps between O3 monitoring points, to different degrees across the world, depending on monitoring equipment budgets. A lower cost small-sensor monitoring solution can provide valuable data within the areas currently lacking in this air quality information. Data validity is typically demonstrated by comparison with a local reference station, although AQMesh is also widely used where no reference data is available.
O3 at ground level is formed by reactions with nitrogen oxides (NOx) and volatile organic compounds (VOCs) from traffic and industrial emissions in the presence of sunlight. As such, hotter, sunnier weather can dramatically increase O3 pollution.
The World Health Organisation (WHO) currently states the daily limit of O3 levels to be 100μg/m3 over an 8-hour mean and advise that prolonged exposure to high levels of O3 can have severe effects on human health, including causing asthma, inflammation of the airways, reduced lung functionality and lung disease. Measuring O3 as a part of an air quality monitoring routine is therefore becoming increasingly important, especially in hotter climates and areas of increased VOC emissions.
O3 can be complicated to measure due to its high sensitivity to environmental conditions and cross-gas effects. Most small sensors for measuring O3 are either electrochemical or metal oxide, but electrochemical sensors (such as those used in AQMesh) have the advantage of low power requirements and can therefore be installed more flexibly. AQMesh pods are compact, wireless units and are available with a variety of power options, including solar panels, which allow them to be installed exactly where monitoring needs to take place.
During summer 2018 AQMesh has been measuring ozone at hundreds of locations across five continents and co-location comparisons show consistently high levels of accuracy. To quote two of many such studies, in an industrial region of the USA, AQMesh O3 measurements compared to FEM gave an R2 of 0.97, and in a similar comparison study in Western Europe the R2 value for O3 was 0.95. AQMesh pods measuring gases can run continuously for over two years using a battery but other power options are available, including solar. Particulate matter (TPC, PM1, PM2.5, PM10) can also monitored with an AQMesh pod, alongside gases including NO, NO2, O3, CO, SO2, CO2 and H2S, as well as pod temperature, RH% and pressure.
The accuracy of AQMesh readings has been proven through an extensive series of global co-location comparison trials and is the proven, commercially available low-cost air quality monitoring system for both pollutant gases and particulate matter, as well as simultaneously monitoring a range of environmental conditions.
On Sunday 13th May 2018, Cardiff Council organised a car-free day in the city’s central area. As a result of this event air quality monitoring data showed an average 69% drop in nitrogen dioxide (NO2) – one of the pollutants of greatest public health concern. Seeking a better understanding of the relationship between air quality and traffic, Cardiff Council hired three AQMesh air quality monitoring pods from Air Monitors Ltd. The instruments were located on streets impacted by the day’s event, and within two of the Councils Air Quality Management Areas (AQMAs); City Centre & Stephenson Court, Newport Road. The instruments continuously recorded air quality at these locations for 20 days before, during and after the event.
“In comparing the results obtained during the Car Free Day Event with results from the following Sunday (20th May) , the monitor on Duke Street showed an 87% reduction in nitrogen dioxide, the monitor in Westgate Street showed an 84% reduction and the third monitor, which was located less centrally from the main road closures, in Stephenson Court, showed a 36% reduction,” commented a Specialist Services Officer, working for Shared Regulatory Services (SRS) on behalf of Cardiff Council . “Comparing the car-free datasets with those of the following Sunday (20th May); the daily average nitrogen dioxide levels recorded by two of the monitors situated within the City Centre AQMA exceeded the EU yearly average limit (40 µg/m3), but on the car-free day, these two monitors measured daily average figures of just 5 and 8µg/m3 of nitrogen dioxide, providing clear evidence that air pollution in Cardiff city centre is generated by traffic.”
Under the European Ambient Air Quality Directive, Welsh Ministers have a duty to ensure that compliance with air quality objectives defined within the directive is achieved. As outlined in Defra’s UK Action Plan for tackling roadside nitrogen dioxide concentrations, July 2017, modelling has indicated that certain road networks in Cardiff fail to meet EU air quality requirements. Cardiff Council has been directed by Welsh Government to undertake a feasibility study, in order to demonstrate how compliance with the directive and its specified limits will be achieved in the shortest time possible. In order to implement air quality interventions, the Council therefore needs to evaluate the sources of pollution so that appropriate interventions can be assessed to ensure that effective mitigation measures can be implemented. At the same time, it will be necessary to engage with citizens to ensure that they appreciate the importance of tackling air pollution.
Nitrogen dioxide and particulates are the main cause of failures to meet EU air quality limits in cities around the world, and it is well known that traffic, and diesel vehicles in particular, are a major source of these pollutants. The AQMesh pods measure a range of gases including nitrogen dioxide, so by monitoring the effect of removing traffic, the Council will be in a better position to implement improvement measures.
Two automatic air quality monitoring stations are located in Cardiff, and the Council supplements the data from these monitors with a network of non-automatic passive diffusion tubes. However, the Specialist Services Officer from SRS says: “The fixed stations can’t provide street-level monitoring at the most sensitive locations, and the use of diffusion tubes does not provide a detailed understanding of daily trends as they only provide a monthly average figure. However, SRS are aware of the capabilities of the AQMesh pods and are familiar with the accuracy and flexibility that they are able to deliver, which is why they were chosen for the car-free day project.”
In order to assure the quality of the monitoring data, the AQMesh pods that were employed during the project were checked against a reference station and were found to have performed very well. “The pods are small, lightweight and battery-powered which makes them quick and easy to deploy,” the Specialist Services Officer adds. “This is crucial to our work because it gives us the ability to site them on lamp posts so that they measure the air that people are breathing. In addition, they are web-enabled which means that we can monitor air quality in almost real-time; providing a unique insight into the specific events that impact air quality.”
It has been estimated that around 40,000 people in the UK die prematurely as a result of air pollution, mainly in the larger towns and cities. In Wales, the urban areas exceeding EU limits include Cardiff, Swansea, Port Talbot, Newport, Chepstow and Wrexham.
Following completion of the monitoring work in Cardiff, SRS has had requests for the data from a number of organisations, and are keen for the work to be publicised as widely as possible. Highlighting the importance of citizen engagement, the SRS Specialist Services Officer says: “A wide variety of potential measures are available to combat air pollution in Cardiff, but many involve inconvenience for members of the public and cost to the public purse, so we need those affected to be on-board with the measures being taken. We are also hoping that the public will be keen to help, by participating in car-share schemes for example.”
Extensive research has shown that indoor air quality is often worse than outdoors. Closed system buildings trap harmful particles inside, and external air intakes can bring in more polluted air from outside.
Whilst many heating, ventilation and air conditioning systems (HVAC) use particle filtering, managed through air exchanges, they can often worsen levels of polluting gases, such as NO2 – now classified by the World Health Organisation as a Class 1 carcinogen. Natural ventilation systems have no particulate filtration at all, and buildings are also frequently completely shut up all night with no ventilation running, trapping the pollution that has built up over the day.
Unlike outdoor air quality (which the government is responsible for), indoor air quality is the responsibility of the building owner or manager, and with research proving that poor air quality has a significant impact on human health, air pollution should be a key factor of employee health & safety.
Future Decisions has teamed up with AQMesh and UK distributor, Air Monitors Ltd, to supply pollution mitigation to improve indoor air quality. Future Decisions has developed patented smart management strategies that aim to reduce internal air pollution by 30% – this is usually enough to bring the air quality within UK & EU regulatory levels, and often within the World Health Organisation levels.
AQMesh measures NO, NO2, O3, NOx, CO, CO2, SO2, PM1, PM2.5, PM10, temperature, pressure and relative humidity in a small pod which can be mounted both indoors and outdoors on a wall or post. Batteries, solar power and DC power options give flexibility of mounting anywhere. AQMesh was designed to offer an easy-to-use air quality monitoring system that can deliver localised real-time readings, improving the accuracy and scope of gathering air quality data in order to support initiatives to reduce air pollution and its risk to human health.
Minnesota Pollution Control Agency (MPCA) has purchased fifty AQMesh pods to measure key air pollution gases and particulate matter across fifty different zip code areas. These small sensor air quality monitoring systems measure NO, NO2, O3, CO, SO2, PM1, PM2.5, PM10, temperature, pressure and relative humidity and will be installed – one per zip code – around the twin cities of Minneapolis and Saint Paul. The two-year project, funded by a legislative grant*, is to supplement the air quality information available to the public.
Deployment across the 50 zip codes has been mapped out after several public meetings involving the local community to determine where residents felt monitoring was needed. The small yellow triangles represent the points which local residents asked for sensors to be installed, and the green dots indicate the planned installation site based on the infrastructure available for mounting the AQMesh pods.
“This project is about understanding small-scale differences in air pollution in urban areas in order to minimise exposure to harmful air pollutants, particularly for vulnerable communities. The Assessing Urban Air Quality project will use new air monitoring sensors to broaden our knowledge about air quality in Minneapolis and St. Paul”, commented Monika Vadali, Ph.D, who is leading the project.
The pods are currently installed at the Blaine airport Federal Equivalent Method (FEM) station so that AQMesh readings can be compared to and validated against air quality readings taken using this US approved methodology, with scaling then applied if necessary. The MPCA team intends to install the pods in each zip code during the next month or two. The pods will be powered using a bespoke solar power pack: 30W panels have been specified for such a northern location, compared to the 15W normally required to supply the low-power AQMesh platform. The pods can be battery powered but 12V DC supply was specified, given the 2-year project timescale.
The pods were installed in November 2017 and have achieved 100% uptime to date, including during severe weather conditions, with temperatures below -25°C / -15°F and heavy snow. Initial comparisons against co-located pods show a high level of pod-to-pod precision, with an average R2 of 0.94 for NO2, 0.92 for O3 and 0.93 for PM2.5.
The 50 pods have been compared to the FEM station in two batches of 25, and the first batch of comparisons show an average co-location comparison correlation R2 of 0.74 for O3 and NO2, 0.86 for PM2.5, 0.93 for PM10 and 0.82 for NO. The reference CO showed a baseline shift part way through the comparison period, so that comparison is being reviewed. The SO2 R2 was depressed by a max FEM reading of 2.5ppb, with low FEM resolution, but AQMesh readings were within +/- 2ppb of reference.
The MPCA team is setting up an API connection to the AQMesh server, allowing air quality data to be streamed, near real-time, to the MPCA server, from which it can be published.
AQMesh is in use at various locations in the USA, as well as 35 other countries. The pods deployed in Minnesota are the current production version (v4.2.3).
More information about the MPCA project is available at https://www.pca.state.mn.us/air/assessing-urban-air-quality-project.
* The project is funded by a legislative grant: Environment and Natural Resources Trust Fund (ENRTF) M.L. 2017, Chp.96, Sec. 2. Subd.07b
The team at AQMesh continue to receive many enquiries from smart city initiatives and are concerned that integrators risk undermining entire projects by distributing meaningless or misleading air quality information.
“Many of the people I speak to are used to dealing with sensors that are easy to ‘plug and play’ and expect to be able to do the same with air quality sensors. This is not helped by the fact that most air quality sensors, sensor systems or ‘nodes’, on the face of it, offer very similar specifications”, comments Amanda Billingsley, AQMesh Director. “Quite understandably, IoT professionals do not generally have a background in air quality measurement and are not aware how notoriously difficult it is to get good air quality readings from small sensors, particularly nitrogen dioxide which is known to be so harmful and a key component of diesel fumes – now classified by WHO as a carcinogen.”
Most of the air quality sensors that are small, cheap and low enough energy for IoT applications also have limitations, such as the influence of rapidly changing temperature and cross-gas effects, and a significant level of experience is required to apply the corrections needed to get useable real-time air quality data. At this stage there are two options: one is to try to deal with the challenge in the measurement hardware, such as managing the conditions in which the sensors operate, but this often leads to large and expensive hardware. The other option is smart cloud-based correction algorithms.
Because of the length of time it has been in the field and the huge variation in environments in which AQMesh has been used and validated / corrected, AQMesh is acknowledged through independent studies to be further down this route than any other small sensor system. Even smart city projects which aim to deliver ‘high level’ air quality information, such as ‘the air quality is better here than there’ or some traffic light system, need to be confident that such conclusions are correct if they are not to be challenged by local authorities and stakeholders.
AQMesh is being used in various smart city and IoT projects around the world. In a collaborative smart city project in Cambridge, UK, AQMesh data was analysed by Professor Rod Jones from the University of Cambridge. “Because we know that all the pods read the same and because we have a comparison between one pod and a reference instrument we can say that all pods are working equivalently across the city. What we are seeing is correspondences in excess of 0.7, 0.8, against reference – and that is very good for straight out of the box”, commented Professor Jones.” The study shows that AQMesh can help cities manage air quality, for example by distinguishing between locally and regionally generated pollution, as well as publishing air quality information for the public.
AQMesh measures NO, NO2, O3, NOx, CO, SO2, PM1, PM2.5, PM10, temperature, pressure and relative humidity in a small pod which can be mounted in a post, on a wall, outdoor or indoor. Batteries, solar power or 12V DC power options give flexibility of mounting to capture air quality data from any point in a smart city or elsewhere.