A network of sensors has been set up in Newcastle in order to give policymakers a more accurate picture of the air being breathed by children.
The project is a collaboration with Newcastle University and Newcastle City Council who have installed 22 air pollution sensors outside schools that are located close to major roads.
The data will be collected by Newcastle University’s Urban Observatory, the team will then use this information to help engage the children who are being directly affected and give them a voice as to how their cities should be planned in the future.
The Urban Observatory is the UK’s largest urban experiment collecting data about 60 different urban indicators, everything from energy use, rainfall and flooding to air pollution and traffic flow.
Currently, the Urban Observation has deployed over 3,600 sensors across Newcastle, including AQMesh air quality monitoring systems*, adding 5,000 new observations ever minute.
Eugene Milne, director of public health at Newcastle City Council said: ‘Poor air quality harms everybody’s health, and young people are among those most at risk, so we’re very pleased to be working with the University and young people across the city to address this.’
‘As well as raising awareness of the issues, the project will also aim to encourage more active travel and fewer car journeys, particularly on the school run.’
‘This project will help us to monitor just how much pollution is in the air around schools and enable us to get views of the children who are directly affected on what else could be done to tackle the problem.’
Sean Peacock, who is based in Newcastle University’s Open Lab has said: ‘Children themselves are far from oblivious to the impact that air pollution is having on their health and their futures.’
‘The school climate strike shows that young people are forcing air pollution and the climate crisis to the top of the political agenda.’
‘Urban planners and politicians are often hesitant to work with children, but they shouldn’t be.’
‘We need to embrace their creativity and passion to take radical action on air pollution and climate change. More, now than ever, we need the original ideas that only children can bring.’
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.
*Original news published in September 2018.
Last month Environmental Defense Fund Europe (EDFE) together with Mayor Sadiq Khan are releasing the second wave of data from Breathe London, an ambitious collaborative project to measure and map air pollution across the capital.
In addition to nitrogen dioxide (NO2) measurements from the network’s 100+ stationary AQMesh pods, the interactive map now includes preliminary data from the Google Street view car drives as well as current and average pollution data for fine particulate matter (PM2.5).
The new data confirms a concerning trend: Air pollution across the capital remains dangerously high. Four out of every five pods, including 90% of schools in the network, are on track to exceed World Health Organisation (WHO) annual guidelines for PM2.5, which is linked to a wide range of adverse health effects. Additionally, preliminary analysis of the mobile data shows NO2 is on average over 50% higher on major through roads than quieter, local roads.
The findings corroborate what EDFE has been saying for some time: Bold action at the national level is needed to cut pollution and create healthy, breathable cities.
Small airborne particles like dust, soot and drops of liquids can create PM. Most PM pollution formed in urban areas is from fossil fuels used in vehicles, construction equipment, heat & power (including wood burning) and commercial cooking.
PM2.5 is made up of tiny particles, which penetrate deeper into the lungs and are linked to lung disease, heart attacks, strokes, asthma and cancer, as well as shorter life spans. This pollution is particularly dangerous for young people – studies show that PM₂.₅ exposure can impair childhood lung development.
Breathe London’s data from the stationary network suggests that over 80% of the pods are likely to surpass WHO long-term guideline for PM2.5. In other words, the annual average concentration of PM2.5 pollution – at the vast majority of measuring sites – is at unsafe levels.
Moreover, although thresholds for PM have been set as general guidelines, there is little evidence to suggest a safe threshold exists below which there are no adverse health effects. Despite the recognition that PM is not safe at any level, it is currently legal in the UK to have pollution levels above what is recommended by the WHO.
Since autumn 2018, two specially-equipped Google Street View cars have been driving London’s streets to measure air pollution. Data from the drives undertaken so far are now visible on the map.
When comparing pollution readings from busy versus quieter streets, preliminary analysis reveals NO2 is on average over 50% higher on busy major through roads than on quieter, local roads*. Like PM, pollution from NO2 is linked to a variety of health impacts, including aggravating asthma and adversely impacting lung function in children.
Amanda Billingsley, Managing Director of Environmental Instruments, the company that manufactured the AQMesh pods, said: “This is a great example of what can be shown by data from a network of stationary small sensor air quality stations, delivering insights that help government and citizens to take effective action to transform pollution exposure levels.
“We have supplied networks of these small monitors in various countries, but it is great to see the potential impact of hyperlocal data – enabling the assessment of air pollution on a street by street basis – in our own capital city.”
The Breathe London data will also be available on the new Air Quality Data Commons (AQDC), an open-access data platform where people can share and use data from low-and medium-cost air quality sensors.
*Comparison assumes error is random. Additional analysis will be conducted after mobile data collection concludes at the end of October 2019.
A version of this article ran on Environmental Defense Fund Europe’s blog on 22 Oct, 2019.
Whilst not the only AQMesh pods still in regular use since the product was commercially launched in 2013, two AQMesh pods are still in use in Spain and demonstrate the long life of this small sensor air quality monitoring system.
Over the last six years, the two pods have been loaned by AQMesh distributor in Spain, Envirodata, to a number of customers for trials and demonstrations, as well as being involved in a range of projects.
In one of these studies the pods were selected to determine how accurately small sensor systems could measure ambient levels of NO2. The collaborative research between the European Life Photoscaling Project, Tecnaire-CM, Greater Madrid Region and Madrid City Council sought to assess the effectiveness of different photocatalytic pavements in reducing levels of NO2 pollution. The AQMesh pods were co-located with two of the region’s larger air quality monitoring stations under traffic and urban background conditions to compare AQMesh readings with reference and calibrate field readings. A paper was published in August 2018 as a result of this study, which determined that with local calibration AQMesh meets the Air Quality Directive’s standards of accuracy at high concentrations of NO2.
These very first AQMesh pods have also been used to determine baseline air quality levels for the La Nucia project in Alicante, in anticipation of the development of a new sports facility. More recently, one pod has been used to evaluate levels of ozone (O3) during the hotter weather in an area within San Agustin, and the other is currently being used by the Madrid Regional Government. Previously, the municipality of Madrid used AQMesh to measure air pollution as part of a traffic reduction scheme, including to reduce speed limits and restrict access to downtown Madrid.
Luis Lombana of Envirodata comments “AQMesh technology is providing us with a unique solution to local air quality monitoring. The combination of compact hardware with advanced data processing algorithms makes AQMesh the best system for mapping city-wide pollution. We have been using these two AQMesh pods for demonstrations and projects since 2013. They have been upgraded by the manufacturer on a few occasions and we are pleased to be able to offer the best AQMesh performance to users with these two old friends. We have no plans to stop using them although we now also sell units with the additional options available, such as PM monitoring.”
The two pods were initially built to measure NO, NO2, O3, CO and SO2, powered by an internal lithium battery, which powers a ‘gas only’ pod for over two years. From 2015 the pod was able to take advantage of developments in the electrochemical sensors, particularly factory sensor characterisation introduced in 2015 (v4.0) and the ozone filter introduced to the NO2 sensor in 2016, which dramatically improved discrimination of O3 and NO2, particularly with the AQMesh proprietary data processing algorithm v4.2. The pods will now be upgraded remotely (a setting change on the AQMesh server), with full traceability, to v5.1 which offers significant improvements in accuracy at higher temperatures.
As well as the original 5-gas suite of sensors, AQMesh can now offer two additional gases – H2S and CO2 – as well as particulate matter (PM1, PM2.5 and PM10), plus noise, wind speed and direction. Other power sources are available with solar being the most popular.
AQMesh pods have been operating in the field since 2013, and so far have been active in over 60 countries in a range of air quality applications. The pods have always been built to a rugged and robust standard, with hundreds of pods installed for years in city centres around the world. The inconspicuous units generally avoid vandalism, damage or malfunction, and in one instance a customer’s pod has still continued to function and transmit data despite being crushed during an accident. They have also proven to withstand extreme weather conditions, continuing to work under several feet of snow during the North American winter and the hot desert climates in the summer months in Australia, South Africa and the Middle East.
A study published in the Journal of the American Medical Association has found that long-term exposure to poor air quality can have the same damaging effect as smoking 20 cigarettes a day, with air pollution shown to be more dangerous than passive smoking.
Many employees are exposed to poor air quality on a regular basis and employers are often unaware of the risks and what they can do to manage them. A new generation of air quality monitoring equipment is now available for measuring the levels of common air pollutants in the immediate areas where staff are working.
Employees working close to areas of high road traffic, particularly with poor air circulation, are especially vulnerable to the effects of pollution. As well as being trapped indoors or brought in through ventilation systems, pollutants can also build up in outdoor spaces, particularly in cities with high buildings, leading to exposure levels which may exceed limits set by the World Health Organisation (WHO).
Diesel fumes were classified as a Class 1 Carcinogen by the WHO in 2017, after it found that people exposed to diesel fumes at work were up to 40% more likely to develop cancer. As such, employers can now be sued if their employees develop cancer later in life as a result of exposure, as reported by The Sunday Times following the reclassification.
The EU limits for nitrogen dioxide (NO2) exposure are 40µg/m3 annually and 200µg/m3 in an hour, no more than 18 times in a year. Many official measurement stations in cities worldwide report NO2 above the annual limit but less is known about local levels of this pollutant. Because NO2 is produced as a direct result of a source, such as traffic exhaust or diesel generators, levels of NO2 regularly exceed the hourly limit when measured in ‘hotspots’, such as busy road junctions, where it is not practical to install a large air quality measurement station, or on a private site.
Previously, air quality has been likened to passive smoking. The International Agency for Research on Cancer (IARC) determined in 2013 that air pollution is more dangerous than passive smoking, and was now the leading cause of cancer. At the time, the IARC’s Kurt Straif told the South China Morning Post “The air we breathe has become polluted with a mixture of cancer-causing substances. We consider this to be the most important environmental carcinogen, more so than passive smoking.”
Measuring ozone (O3) as a part of an air quality monitoring routine is also becoming increasingly important, especially in hotter climates and areas of increased VOC emissions. O3 at ground level is dangerous and is formed by reactions with nitrogen oxides (NOx) and volatile organic compounds (VOCs) from traffic and industrial emissions in the presence of sunlight. This means hotter, sunnier weather can dramatically increase O3 pollution in urban and industrial areas. The 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. These include asthma, inflammation of the airways and reduced lung functionality, just as the recent studies comparing air quality to smoking has found.
Senior co-author of the study Dr Joel Kaufman, from the University of Washington, said: “We were surprised to see how strong air pollution’s impact was on the progression of emphysema on lung scans, in the same league as the effects of cigarette smoking, which is by far the best-known cause of emphysema.” The professor of environmental and occupational health sciences and epidemiology added: “We really need to understand what’s causing chronic lung disease, and it appears that air pollution exposures that are common and hard to avoid might be a major contributor.”
Teams responsible for protecting staff from exposure to hazards can now understand exposure in relevant locations by installing compact air quality monitoring equipment designed to continuously measure pollution levels in ambient air.
AQMesh pods are small, wireless units which can be mounted on a lamp post, fencing, wall or a similar mounting point close to where staff are breathing potentially polluted air, both indoors and outdoors. Air quality readings are secure and confidential, accessed online by authorised personnel only.
AQMesh has been used on building sites, industrial sites and at roadside locations worldwide, as well as measuring the air intake into office buildings, in order to monitor the air quality of employees working in these areas on a daily basis and helping to protect them.
Minnesota Pollution Control Agency (MPCA) has been monitoring Minnesota’s air quality for a number of years, and it is generally considered to be good. However, MPCA wanted to understand how air pollution varies across small distances in order to minimise vulnerable communities’ exposure to harmful pollutants.
Following project funding* in 2017, earlier this year MPCA successfully installed AQMesh pods across 44 sites in neighbourhoods around Minneapolis and St. Paul, primarily on lampposts in school parking lots, with at least one pod in each ZIP code.
MPCA gives high priority to community involvement and sharing its air quality data with the public. It has launched an online tool allowing citizens to compare pollution levels at different monitoring sites over a given date range. Monika Vadali, Ph.D, who is leading the project, welcomes feedback on the online tool and the wider project and is looking forward to hearing comments from communities where monitoring is taking place.
Prior to being deployed across Minneapolis and St. Paul, the AQMesh pods were co-located against the FEM station at Blaine airport for a number of months in order for the readings to be compared and validated, and for scaling to be applied if necessary. During the co-location period AQMesh showed high levels of pod-to-pod precision, with an average R2 of 0.94 for NO2, despite extreme weather conditions.
For the next two years, the AQMesh pods will monitor and report data on levels of NO2, O3, NO, SO2, CO, PM2.5 and PM10 in 44 areas of Minneapolis and St. Paul to build up a picture of air quality across the cities. Scientists at MPCA will use the data to determine if there are any significant differences in the concentration of pollutants between ZIP codes, if there are any areas with unusually high levels of pollution, and if technology such as AQMesh is suitable for measuring such small variations in air quality.
The study is similar to the Breathe London project in the UK, where 100 AQMesh pods have been deployed across London to publish a real-time map of the city’s air pollution, which has now also been launched online.
For more information about the MPCA project, please contact Monika on (+1) 651-757-2776.
*This is a legislative funded LCCMR project, with support provided by the Environment and natural resources trust fund (Subd. 07 Air Quality, Climate Change, and Renewable Energy ENRTF # 07b).
Partners and collaborators include the city of Minneapolis, the city of St. Paul, Minnesota Department of Health, Minnesota State University-Mankato, and Xcel Energy.
Detailed information on London’s (UK) air pollution is now being published on breathelondon.org, the website for a new collaborative project to paint a clearer picture of the city’s air quality. The readings are being provided by a network of AQMesh air quality monitoring pods supplied and installed by Air Monitors, part of the ACOEM Group.
The AQMesh pods are stationary – mostly mounted discreetly on lamp posts, but the pod data is being supplemented by measurements from instruments that have been installed by Air Monitors in two Google Street View Cars, as they travel the city’s streets.
Visitors to the Breathe London website will be able to view almost live data (within an hour) on nitrogen dioxide (NO2); one of the urban pollutants of greatest concern.
“This is a major step forward,” says Felicity Sharp, Air Monitors Managing Director. “The availability of highly localised air quality data is critical to the empowerment of citizens so that they can make choices that affect the quality of the air they breathe.
“In the past, air quality data has not been sufficiently local to allow most citizens to change the way they live their lives, but with the benefit of this website they will be able to choose where they want to walk, run, play, go to school or even buy a house.
“The data will also help to raise awareness and thereby encourage citizens to choose more environmentally friendly transport modes, particularly in pollution hotspots.
“Importantly, the data will also help national and local government to assess the effectiveness of air quality improvement measures. So this is great news for London, and we hope that it will be replicated in similar smart city projects around the world.”
Schools near Glasgow have been monitoring air quality as part of a project aiming to reduce the levels of pollution emitted by vehicles as they drop off and collect children. The project is part of a ‘Beat the Street’ initiative that was granted £50,000 from a new £1million fund to increase walking, cycling and sustainable travel in Scotland. The overall aim is to cut Scotland’s carbon emissions, improve air quality, reverse the trend towards sedentary lifestyles and tackle health inequalities.
The Environmental Health department of East Renfrewshire Council supplied and installed the three AQMesh air quality monitoring pods that were utilised in the project. The monitoring activity followed initiatives in eight schools organised with SEPA, in which the children designed their own air quality banners as part of a competition.
The banners were then placed outside the schools which were then monitored for two weeks with an AQMesh pod measuring a variety of parameters including nitrogen dioxide – one of the pollutants of greatest concern. The Council’s Richard Mowat said: “We used one of our own AQMesh pods and rented the other two from Air Monitors. The pods are small and easy to install so we were able to locate them close to the areas most affected by parents’ vehicles.
“The results clearly showed significant peaks in pollution during the drop-off periods and it was pleasing to note how well the project was received. We hope that this work will help educate the children and that they, in turn, will encourage their parents to leave the cars at home and walk whenever possible.”
Anne-Marie Absolom is Head Teacher at one of the participating schools – St Clares Primary School. She said: “Our Junior Road Safety Officers, and all of the school staff, are delighted that we have had the opportunity to install temporary air quality monitors in our car park.
“We have been campaigning throughout the year to improve air quality in and around our school. The children have also been learning about the small changes that they can make – changes that will make a big difference to the quality of the air we breathe.
“The results from the monitors have highlighted the specific times of day at which air pollution is most significant, and the Junior Road Safety Officers are now campaigning at these times. The data gathered has been shared with all children in the school and they are passionate about spreading the word and ensuring that air pollution is reduced.”
As well as supplying the monitoring equipment for the project, Air Monitors also provided sponsorship funds for the school banners, and this was reflected in a stunning night-time time display on the roof of Glasgow’s famous SEC Armadillo, organised by SEPA. A variety of images relating to air quality were projected on to the Armadillo’s roof, highlighting for example Clean Air Day 2019, as well as the Air Monitors logo.
SEPA’s Dr Colin Gillespie said: “It has been great to work again with Air Monitors and the councils, raising awareness in air quality around schools, promoting active changes to reduce pollution and encouraging pupils to think about more sustainable forms of travel.”
Following a successful evaluation phase in 2018, AQMesh small sensor air quality monitoring ‘pods’ have been selected for use in a project to control the ventilation of a road tunnel in the city of Marseille.
Supported by the AtmoSud (AirPACA) local air quality monitoring network, the CETU (Tunnel Studies Centre) and AQMesh distributor Addair, eight AQMesh pods were installed in February 2019, monitoring nitrogen oxides NO and NO2, in an innovative experiment in one of the covered sections of the L2 ring road in Marseille. Called “Boreas project”, after legendary ‘dispersing’ winds, this study aims to use pollution measurements near tunnel entrances to activate in-tunnel fans.
Urban planning is increasingly routing vehicles underground. Although this approach eases air quality and noise at some locations – and overall reduces the level of pollution the population is exposed to – there is a risk that residents living close to the tunnel heads are actually exposed to higher concentrations of pollution as air is expelled from the tunnel.
The L2 ring road in Marseille consists of a succession of covered tunnels over 12Km in dense urban areas. The phased project at the Montolivet South tunnel heads will implement a system for the conditional triggering of in-tunnel fans to evaluate its impact on air quality in the zones adjacent to the nearest residents. This approach was tested in 2018, with micro-sensor readings compared at the AirPACA Kaddouze monitoring station. A first phase analyses the pollution without activation of the ventilation system, then a second phase with ventilation.
The aim is to determine the link between ventilation and dispersion of the pollution at the end of the tunnel and to determine the most effective protocol for activation of the ventilation systems based on real-time air quality levels, inside and outside the tunnel. Automated alerts for high NO2 levels are already in place. The feasibility of this approach will also be reviewed by analysing efficiency in terms of cost and energy consumption. In theory, the use of ventilation could improve the quality of air at the head of the tunnel. However, in some weather conditions this could simply displace the pollution and this forms part of the study – analysing the pollution concentration and dispersion in different meteorological and traffic conditions.
AQMesh has been used in other tunnel monitoring projects, including several in the UK, specifically to study ventilation efficiency in road tunnels where pollution can build up if sufficient air flow is not maintained. During the UK projects, AQMesh pods were also first co-located with a nearby reference station to ensure measurements were directly comparable.
The pods were then deployed at different positions within the tunnels and in ventilation ducts, studying how the concentration of pollution changed when air flows were adjusted in varying traffic scenarios. The pods were able to run for up to six months without any maintenance or calibration, despite the very high pollution levels recorded. The results obtained in these studies enabled optimisation of the ventilation settings and helped to reduce energy consumption whilst maintaining cleaner air for tunnel users and maintenance personnel.
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.
Westgate Oxford is a brand new £440m shopping centre comprising of retail outlets, restaurants and a cinema, and was developed as a replacement to the old shopping centre that was demolished in 2016. Having recently opened in October 2017, it estimates it will attract 15m visitors every year.
The AQMesh pods were purchased by the Westgate developer under a Section 106 agreement to monitor levels of NO, NO2 and O3. Oxford City Council’s Air Quality officer, Pedro Abreu, has been using them to supplement information available from other sources. Because the pods are battery-powered they can be mounted at exactly the point in centre where monitoring is required, and easily moved to a new monitoring location when necessary. Pedro Abreu carried out co-location comparisons with a reference station and is very satisfied with the correlations he has seen with the AQMesh pods he is using.
His comments echo those of Professor Rod Jones from the University of Cambridge, who led a project using AQMesh pods across Cambridge to demonstrate how air quality varies across the city. “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 something straight out of the box”, commented Professor Jones.
AQMesh is currently in use in Nicaragua, monitoring air quality in communities living near Masaya volcano. The six AQMesh pods have been used to show variations in volcanogenic SO2 and PM levels at different times and at different locations across the area.
The pods, which have independent power and communications so they can be mounted where required, were installed in March 2017 as part of a research project funded by the Global Challenges Research Fund: Unseen but not unfelt: resilience to persistent volcanic emissions (UNRESP). The project is led by the University of Leeds and is a multi-partner collaboration of several universities in the UK and Nicaragua, as well as Nicaragua’s natural hazards observatory INETER and the Icelandic Met Office.
The Global Challenges Research Fund supports projects focusing on challenges faced by developing countries, aiming to build resilience to natural and anthropogenic hazards. The aim of UNRESP project is to devise an early warning system for dangerously high levels of air pollution, specifically SO2 and particulate matter. As this is a 12-month foundation phase project, the data are not currently being made public but will be put in the hands of local authorities and other stakeholders when the warning system is refined. AQMesh readings are being compared to predictions from a pollution dispersion model, CALPUFF, which requires relatively little computing power. The CALPUFF model has been successfully used for air pollution forecasting at other volcanic sites, such as a recent eruption in Iceland which did not produce ash but emitted twice as much SO2 as all European Union countries combined and caused repeated air pollution in Iceland for 6 months.
“Air pollution is a chronic and serious hazard affecting many developing countries, but there is generally very limited capability to monitor and mitigate it. AQMesh provided us with an opportunity to install the first AQ monitoring system in Nicaragua – the pods are very cost-effective which is of utmost importance for the local setting, yet they provide data that are of high quality. Real-time data on the ground is vital for quantifying and understanding the duration, peak concentration and frequency of high air pollution episodes, which are factors that directly impact human health”, commented Dr. Evgenia Ilyinskaya who is leading the project. The UNRESP team started by hiring five pods for three months via UK distributor, Air Monitors Ltd. as well as purchasing one AQMesh pod for long-term observations. The pod rental has been extended for another three months and the practicality of long-term use of this sort of equipment is being evaluated, including the use of rechargeable batteries or solar power. The team is working closely with local communities and such stakeholders taking custody of the equipment intended to protect their own community mitigates against some risks, such as theft or damage.
Although there is no reference station at the site, diffusion tubes have been used to take measurements which can be compared to the 15-minute average, real-time readings from AQMesh. Whilst EU air quality standards focus on the short-term high concentrations typical of SO2 from an industrial source the UNRESP team is trying to understand the impact of long-term elevated SO2 on the population. Having SO2 measurements with high time and spatial resolution is critical for this and the plan is to potentially create an alert for accumulated concentration of pollutants.
The draft proposal for a follow-on project at the site states the collaboration with AQMesh identified ways of improving the equipment for monitoring volcanogenic pollution, which tends to be much more corrosive than ‘typical’ urban pollution. Dr. Evgenia Ilyinskaya commented, “the AQMesh equipment is extremely cost-effective while providing data quality comparable with EU-certified monitoring. One AQMET station was purchased during the UNRESP foundation phase and it will remain in Nicaragua to form part of the permanent AQ network.”
It is generally accepted that whilst measurements from air quality reference stations are highly accurate, they are not sufficiently location-specific. Key pollutants – such as NO2 and PM2.5 – vary dramatically over short distances and time intervals, but the large size, maintenance requirements and relatively high cost of reference equipment limits the places it can be installed. Diffusion tubes can offer a very cheap alternative and are much easier to install in specific locations, however they only offer a single reading over a number of weeks, and air quality professionals therefore rely on modelling techniques to fill the gaps. With research continuing to prove the extent to which air pollution varies significantly over space and time, the answer would be a reliable and accurate tool for taking real-time, localised measurements.
A number of new low-cost air quality monitoring systems are available, each with benefits and shortcomings. It is fair to say that the available sensors, whether electrochemical, optical or metal oxide, are all working at or close to their limit of detection to provide the low ppb or µg/m3 level of sensitivity required for any of the common ambient air quality applications. However, several systems offered for these applications provide readings in ppm or even % level readings – which clearly makes them inappropriate for ambient air monitoring. Some are also not fit for long-term outdoor use, as they are not fully weather proof or cannot cope with the expected temperature ranges. However, at least one system – AQMesh – does operate across a wide range of conditions and territories, so having established that a viable product exists, can it deliver the accuracy required?
Performance is clearly a major consideration for any user and comparing readings from a lower cost system against a reference station is the obvious place to start. One immediate challenge is ensuring meaningful results. Particularly in roadside applications or where there is an immediate source of pollution, all sensors and intakes must be within a metre of each other and at an equal distance from the immediate source. Most sensors, not unreasonably, also require an uninterrupted air flow around them – mounting immediately above hot or wet surfaces will not give accurate readings. On the other hand, some limitations of reference equipment come to the fore when comparing with a different type of measurement. For example, single channel NOx analysers switch between measuring NO and NOx, calculating NO2 as the difference. This switching can have dramatic effects on readings for the two gases (which are measured separately and directly by other sensors) at short reading intervals, such as 1 minute. Similarly, any differences in clock synchronisation or reading averaging protocol (time beginning or time ending) can make the difference between a regression comparison R2 of 0.9 and 0.1, which can render comparisons meaningless.
Comparisons of particulate measurements are also problematic due to the range of reference-equivalent methods available and the limitations, in many ways, of the reference method itself. Since the expanded uncertainty of the reference equivalent measurements for PM10 and PM2.5 allows up to 25%, this should be borne in mind when making comparisons with lower cost particulate sensors. Overall, for both gases and particulate matter, if several identical low cost systems are co-located, the user should expect a high level of repeatability (R2 > 0.9) and should expect to be able to adjust accuracy by ‘calibrating’ – adjusting slope and offset – against a co-located reference/equivalent station. Some systems, such as AQMesh, then allow this scaling adjustment to be applied automatically to all future readings, minimising the need for manual data correction. Access to a calibrated reference station and careful co-location is currently key to getting value out of any of the current generation of emerging sensor systems, although the objective of good accuracy without the need for a reference station is being actively pursued.
First questions about these systems often include ‘How do I run gas through it to calibrate it?’ and ‘Can I calibrate (or test) it in the laboratory?’ In systems such as AQMesh the air sample is not pumped, for good power-saving reasons (low power is essential for battery operation), and so it is not obvious how a conventional gas calibration would work. More importantly, although the sensors generally do give very good results in laboratory tests with known dry, single gases, these bear no relation to real ambient field measurements with a combination of damp, humid gases at potentially varying temperature and pressure. Overall, there is no proven substitute for co-location with a reference station. Even with all of these considerations, some of these small, lower cost air quality systems, such as AQMesh, can deliver very impressive comparison results and provide a new source of air quality data. Those with in-built power and communications offer genuine freedom to gather measurements from any location and research teams worldwide are using such systems to understand pollution around cities, inside and outside buildings, at different heights, in street canyons, around industrial facilities and within neighbourhoods, at different times of day, and so on. This new granularity of measurement and flexibility of location gives air quality management teams a real tool to carry out ‘before and after’ studies and evaluate a range of policy or pollution mitigation activities. Where a number of sensor systems are used, and particularly in combination with wind speed and direction information, the relative measurements and source distribution can provide very powerful insights about where to target pollution mitigation activity.
One such low cost outdoor air quality monitoring system offering this type of flexibility is AQMesh, which has proven its repeatability, accuracy and performance through a series of these careful co-location comparisons with calibrated reference stations in a variety of global locations and applications. The small size, battery power and wireless communications technology mean users can benefit from reliable and accurate real-time, localised air quality measurements in a broad range of studies.
How accurate is ‘accurate’?
One area of discussion is what level of accuracy is ‘good enough’. Although this depends on the application, it is still tempting to look for a very high level of agreement between the low cost sensor system and reference equipment. Whilst this may be the goal, the lower cost systems are considerably cheaper and have the benefit of being correctly located so perhaps it is better to have slightly less accurate readings from the right location than highly accurate readings from the wrong location? For some applications it is really only the relative readings which are required, and systems like AQMesh provide very high levels of precision between identical systems. Or it may only be appropriate to provide a ‘traffic light’ indication for communicating air quality to the public. Until more general guidance is available, users will have to take a view on accuracy relevant to their application.
Publishing air quality data
Another area of confusion is regarding data privacy vs online publication of air quality data. Most of the new air quality systems take advantage of remote data management and online access. This makes sense for a number of reasons. Hard-wired communications infrastructure is a barrier to freedom of location and new systems generally communicate either using the mobile network, radio or wi-fi. Online access to data is also very convenient and less resource hungry. Few of us who readily use mobile phones, online banking and many of the commonplace applications of modern life fully understand security of communications and the reality of data hosting. The bottom line is that air quality data from sensor systems using wireless communications can be as secure as any other online application. Confusion is caused by the systems which are focused on citizen engagement and offer automated sharing and publication of data, but these are the exception and in most cases, such as AQMesh, data is private and secure.
The new generation
Current low cost air quality sensor systems are a very mixed bag. Some products may well appear to offer the same measurements and even claimed accuracy as the more thoroughly developed and tested systems and the user has little choice but to ask searching questions and ask for demonstration of performance and reference projects before purchasing. But the need for such systems is clear and performance is already good enough for many leading institutions and organisations to be actively using the technology. Sensor and sensor system manufacturers are seizing on every new shared comparison dataset and development in technology to make further improvements. The insights that these sensor systems can offer are real and relevant and there is no substitute for trying the technology in any given application to see what it can offer. Many users have found that one insight can lead to another and, working with a clear understanding of the strengths and weaknesses of the systems, the benefits of making a start with this new tool are overwhelming.
The emergence of sensors capable of measuring the gases and particles that make up air pollution, especially in cities and industrial areas, has driven many academic studies which evaluate the sensors and compare performance against reference methodology. Such projects provide valuable and thorough assessment, but they currently work slower than the pace of low cost sensor system development. In addition, EU and US authorities are developing methodology appropriate for certification of such systems. In the meantime, practitioners across a number of fields are adopting AQMesh as the leading commercially available sensor system, and generating valuable information to support policy and commercial decisions.
The obvious and first application for this sort of technology is in identification and management of pollution ‘hotspots’ in cities and collecting background measurements across a much wider range of locations than has previously been possible. UK local authorities and similar bodies in a range of countries have been using AQMesh to monitor specific locations for NO2 and now particulate matter, evaluating mitigation methods, such as barriers between traffic and pedestrians. These studies have often been in conjunction with academic teams who have also investigated issues such as the impact of industrial chimneys close to high rise buildings and pollution at different levels of multi-storey residential buildings. One project uses AQMesh to support development of a walking-to-school campaign, comparing different walking routes and educating parents. AQMesh has also been used to minimise NOx and particulate matter inside buildings through management of building ventilation systems.
Building contractors have been searching for an instrument to measure dust construction sites, which does not require an external power source, and a number of projects are now using AQMesh for this purpose. Civil engineering applications include monitoring pollution in road tunnels and associated ventilation ducts. Studies in several countries, including Scotland, Ireland and Greece focus on understanding the relationship between traffic volumes, mitigation measures and air quality. Local air quality data, used in combination with wind speed and direction information, can provide powerful pollution source attribution, relevant to fence line monitoring of industrial sites, airports, and so on.
These new sensors systems can provide a new stream of information, complementary to and calibrated by reference stations. But being self-sufficient in terms of power and communications, they offer freedom of location and open new opportunities.
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Transport Scotland recently piloted the installation of low cost air quality sensors at several locations near the trunk road network.
AQMesh pods were deployed at these various roadside locations to monitor the levels of pollutants. At the same time, traffic data was collected to allow comparison between traffic volume, speed and classification.
Analysing the traffic data indicated good correlation in certain circumstances, with lower speeds coinciding with higher readings in some pollutants. When cross-referenced with AQMesh data, it was found that the air pollutants linked with the most harmful traffic emissions are NO2 and PM2.5.
The full findings of the Collaborative Sensor Rotation Programme (CSRP) are available on the Transport Scotland website.
Read the case study.
Situated in the south west of Wales (UK), in a largely rural area bordering the Brecon Beacons, Carmarthenshire’s air quality is predominantly good. However, there are areas of concern where major roads pass through some of the County’s larger towns, including Llanelli, Carmarthen and Llandeilo, where air quality is dominated by the effects of road traffic. The County Council is therefore testing new monitoring technologies so that it will be better able to track the effects of improvement measures.
Carmarthenshire County Council operates a network of passive diffusion tubes as part of its commitment to Local Air Quality Management under Part IV of the Environment Act 1995. However, in 2013, Air Monitors supplied the Council with a new type of air quality monitor, ‘AQMesh’, that is able to provide continuous air quality readings for a range of important parameters. This new technology is small, wireless, lightweight and battery powered, which means that it can be quickly and simply mounted in almost any location.
The Council’s monitoring programme has identified Nitrogen Dioxide (NO2) from traffic emissions, mostly diesel vehicles, as the pollutant of greatest concern. A number of locations in the centre of Llandeilo have been shown to be in breach of European air quality standards, so an Air Quality Management Area (AQMA) has been established in the town. Whilst NO2 levels are not sufficiently high to cause immediate health effects, the current levels could cause adverse health effects over the long term, particularly in people suffering from respiratory conditions such as asthma and chronic obstructive pulmonary disease.
NO2 reduction by about 25µg/m3 is the main objective of the air quality action plan, but the Council is determined to ensure that all pollutants remain at safe levels, so the ability of the AQMesh to monitor a wide range of parameters (Ozone, Carbon Monoxide, Sulphur Dioxide, Nitrogen Monoxide, Nitrogen Dioxide, Temperature, Humidity and Atmospheric Pressure) is a major benefit.
Stephen Hoskin from Air Monitors says: “There are a number of important new features in AQMesh that are fundamentally changing the way that air quality is monitored; firstly, it can be located where air quality matters most – where people are breathing.
“Secondly, in comparison with large reference stations, with only a small drop in levels of accuracy, the cost of monitoring is reduced dramatically, which means that users will be able to measure air quality in more locations, and this will reduce the UK’s current dependence on modelling to ‘guesstimate’ air quality.
“Finally, by providing near real-time data over the internet, useful air quality data can be made available to a much wider audience via smartphones, tablets and computers.”
AQMesh in Carmarthenshire is being operated by Oliver Matthews, one of the Council’s Environmental Health Practitioners with specific responsibility for air quality. He says: “In the past we have not continuously monitored this range of parameters because doing so would have involved the installation of a large, expensive air quality monitoring station that would have probably required planning permission.
“These reference stations offer high levels of accuracy, but come with large capital and operational costs, and cannot typically be moved, whereas the AQMesh can be quickly attached to a lamp post or other item of street furniture at a fraction of the cost.
“Alternatively, we could install passive diffusion tubes, one for each parameter of interest, but the disadvantage of this method is that the tubes are left in place for four to five weeks, so we are only provided with an average figure over that time, with no indication of the peaks and troughs that occur. For example, a recent road closure resulted in the diversion of traffic and, with the benefit of AQMesh, we were able to track a significant short-term rise in NO2.”
With the assistance of key stakeholders, the AQMA draft action plan has identified a number of options to improve air quality, and the AQMesh unit has been installed in order to help assess the success or failure of each initiative.
Interestingly, the development of the AQMA action plan benefitted from essential gas main works that were required in Llandeilo because this involved the closure of the main trunk road (Rhosmaen Street) for a period of up to three months, which provided an opportunity to identify the effects of traffic diversions on air quality.
Options that are being considered as part of the action plan include improving traffic management and seek to prevent vehicular ‘stop/start’ and promote a smooth flow of traffic. Typically, these options could include the provision of extra parking outside of the AQMA, the removal of some on-road parking within the AQMA, better parking enforcement, relocation of bus stops, reviewing pedestrian crossings and improvement of bottle necks.
Summarising Oliver says: “The network of diffusion tubes has enabled us to identify hotspots, and these are the locations at which the AQMesh will be of greatest use because we will be able to study trends and look for the causes of elevated pollution levels at specific times of the day.
“Data from the AQMesh are provided on a website via the ‘Cloud’ so, looking forward, this technology has the potential to make a major difference to air quality improvements and to the transparency and availability of data. For example, it may become possible to integrate air quality monitoring with automatic traffic management.”
At 8pm on Monday 22nd February, Channel 4 Dispatches revealed that air pollution could be much more dangerous than previously believed. The Dirty Secrets: What’s Really In Our Air? programme features AQMesh pods being used in tests to prove high levels of nitrogen dioxide (NO2) at road traffic hot spots – and even from your gas cooker – which could be a contributing factor for breathing problems and medical conditions, particularly in children, across the nation.
Watch the 30 minute programme, available for the next 29 days.