Global Clean Air

Making the most of sensor data: How tracking performance of lower-cost sensors allows cities to reveal actionable insights about local air pollution

By Dan Peters / Published: February 23, 2022

Lower-cost air quality sensors can be a game changer for cities looking to understand and improve air quality at the neighborhood level. However, issues with accuracy have been a key barrier to their adoption. Our new paper shows how users can make the most of their data by evaluating sensor performance on a continuous basis.

Collocating sensors to track performance

As part of the Breathe London consortium, we installed 100 sensor devices across the city  to measure key pollutants including nitrogen dioxide (NO2) and particulate matter for more than two years. Lower-cost sensors like the ones we installed are more sensitive than reference-grade instruments to environmental factors like temperature, relative humidity, or even levels of other pollutants. That can make their measurements less reliable in some environments, or even in certain seasons of the year.

To make sure our data was both accurate and useful, the Breathe London consortium developed rigorous quality assurance procedures. For our NO2 dataset, the procedures included multiple methods to calibrate the sensors, as well as applying an algorithm to correct for sensitivity to ozone, which the sensor can mistake for NO2.

While most of our sensors were collecting measurements at new locations across Greater London, we also installed two “test” sensors alongside London reference-grade monitors for most of the project. By tracking when data from these “test” sensors deviated from the more expensive reference instruments, we had an indication of how sensors across our network were performing at different times.

In the left panel, the “test” sensor measurements show a large deviation from the collocated reference monitor (right), indicating a period when the sensor was not performing well.

This approach provided a reality check for our pollution data. If the sensor network reported high NO2 values but the “test” sensors were completely off track from the reference at that time, we could infer that the network result may have been affected by poor sensor performance and adjust accordingly. This kind of ongoing sensor evaluation is important. Without it, users could mistake erroneous sensor data as evidence of major pollution events or local hotspots.

Why performance matters

Our NO2 sensors performed well most of the time, producing data that revealed a variety of actionable insights, including:

  • Times of day and days of week with the highest pollution levels
  • Regional pollution episodes (for example, a multi-day period with high pollution caused by weather conditions)
  • Hotspot detection
  • Impacts of sources on pollution patterns at different locations
  • Long-term trends (for example, seasonal changes or year-over-year improvements)

Improving our understanding of air pollution in cities around the world

While the uncertainties associated with lower-cost sensors may make them unsuitable for some applications, our project demonstrates a way to generate actionable insights from sensors. The Breathe London network’s NO2 data shows that with rigorous quality assurance and ongoing evaluation of sensor performance, cities can utilize lower-cost sensors to better understand local air pollution. That can allow more communities to take advantage of this relatively new technology, even if they do not have the resources to purchase a network of more costly  reference-grade monitors.

Also posted in Academic, Monitoring, Science / Comments are closed

Why emission intensity matters

By lpadilla / Published: January 21, 2022

High-intensity emitters disproportionately pollute the air we breathe. Understanding where sources contribute the most potent emissions can help drive smarter clean air solutions.

Cutting the most damaging emissions from the air can be a bit like picking which foods to limit in your diet. You know the concept—fruits, vegetables, whole grains and lean proteins contribute far less to obesity than chocolate cake, cheesy pizza or greasy burgers. Healthy eating means paying attention not only to how much we consume but also the composition of each item.

The same can be true for controlling emissions of harmful pollutants like nitrogen oxide (NO), nitrogen dioxide (NO2) and small particles. Some “high-intensity” sources—like ships, diesel generators and heavy-duty trucks—produce more potent pollution than new, gasoline-fueled passenger vehicles.  In addition, conditions like stop-and-go traffic, larger cargo loads, and driving up hill can increase emission intensity, compared to freely flowing, lighter-duty traffic. Pollution varies from block to block and city to city, so understanding where sources contribute the most potent emissions can help us tailor more effective, local solutions. Our recent paper maps London’s air pollution and hotspots of emission intensity on an unprecedented street-by-street scale.

How to spot high-intensity emissions

In London, our teams used Carbon Dioxide (CO2), a key indicator of combustion, to determine the intensity of NO and NO2 pollution (NOx, in combination). Taking on-road air pollution measurements every second using mobile instruments, we identified local peaks in CO2, signaling recent emissions.  Then we calculated the emission intensity for these events as the ratio of NOx to CO2 concentrations.

Why emission intensity matters

Our measurements coincided with the implementation of Central London’s Ultra-Low Emissions Zone (ULEZ), where highly-polluting vehicles must pay a fee to enter the city center. This policy led to a cleaner vehicle fleet in and around the ULEZ and 35% lower total NOx emissions in the first year, even as overall traffic volume stayed about the same, by effectively reducing the emission intensity of individual vehicles. In fact, the ULEZ has been so successful that the Greater London Authority expanded it to an even larger area.

Emission intensity mapped in Central London. For more information on the image or to read the article, visit the journal Atmospheric Environment.

While the Central London ULEZ and its recent expansion are effective, air quality remains poor throughout London, and hot spots remain. By measuring emission intensity, we understand more about the overall causes of pollution than if we had relied solely on total concentration measurements. By digging deeper, we can show where higher-intensity sources, like heavy-duty diesel, are having a disproportionate impact on air quality. For example, we saw higher-intensity pollution along the Thames river near shipping piers, heavy construction sites and poorly-timed lights that caused traffic jams.

Crafting smart policies to combat air pollution

Equipped with local, street-scale emission intensity data, in addition to more typical total pollution measurements, policymakers in London and beyond can craft tailored solutions to cut air pollution and improve health. Some changes are easy, actionable and don’t require legislation—like fixing poorly-timed traffic lights or enacting anti-idling rules at passenger bus terminals. Other fixes—like limiting the number of warehouses that can be sited in one area to reduce truck traffic, staggering the timing and location of construction projects in order to reduce emissions from heavy equipment, electrifying buses or reducing the number of used, dirty vehicles in operation—would require more political will.

While we need to reduce all combustion-related emissions to achieve air quality and climate goals, using new methods to identify emissions intensity allows leaders to see where the dirtiest sources are, so they can focus initial efforts where tangible impacts are possible.

 

Also posted in Science / Comments are closed

Discover what’s causing air pollution in London with this interactive map

By Elizabeth Fonseca / Published: September 7, 2021

Ever wonder where air pollution in your neighbourhood is coming from?

We’ve been working on a new Greater London map that displays detailed information on the sources of health-harming air pollution. Search for or click anywhere on the map to get a breakdown of pollution sources – for both nitrogen oxides (NOx) and fine particulate matter (PM2.5) pollution – at that particular spot.

What does the map display?

The map uses data produced by Cambridge Environmental Research Consultants (CERC) using the ADMS-Urban model as part of the Breathe London pilot project.

Based on modelled data for 2019, the map:

  • Displays an estimate of annual average NOx and PM5 pollution levels in London for major different sources of pollution.
  • Allows users to see a calculation of the pollution that people breathe, depending on where they are in the city and separated out by source category.
  • Provides distinct visual ‘layers’ for more than 20 individual sources (e.g., taxis, Transport for London buses, commercial gas), as well as grouped sources (e.g., all diesel vehicles).

The modelled data, which takes into account factors like wind and weather, is available on a 10 metre grid across London and provides the annual pollution concentrations experienced at 1m above ground level.

Which sources are included?

  1. Road transport: Cars, buses, lorries, etc. and particularly those that run on diesel fuel.
  2. Other transport: Other means of transportation that don’t involve the road, such as planes, trains and ships.
  3. Commercial and domestic fuel: Heating and powering of indoor spaces like our homes, offices and shops by combustion of fuels such as gas, oil and wood.
  4. Industrial and construction: Waste management activities like energy from waste plants and ‘Non-Road Mobile Machinery,’ i.e., construction sites and machines like diggers, excavators and diesel generators.
  5. Miscellaneous: Other smaller sources like sewage treatment and smaller household sources
  6. Background: Pollution produced outside of London that has been blown in by the wind.

Pollution health impacts

The map displays two pollutants: NOx and PM2.5. NOx are a sum of nitric oxide (NO) and nitrogen dioxide (NO2) which, along with PM2.5, are the main air pollutants of concern in London. They are harmful to human health and are associated with adverse health outcomes like asthma, strokes and cancer.

London also has emissions inventories for NOx and PM2.5, meaning there is a detailed list of all the activities contributing to these pollutants across the city. The model that is behind the dataset requires these emission inventories.

This is the first time that modelled pollution sources data has been displayed in this detail across Greater London on an interactive public map. With a better understanding of which activities are causing pollution and where, leaders and communities can develop targeted solutions that clean the air and protect people’s health.

Please see here for a recorded demo on how to use the map, explain how the data was calculated and answer your questions.

Also posted in Government Official/Policymaker, UK / Comments are closed

New analysis reveals true ‘reach’ of London’s Clean Air Zone

By Oliver Lord / Published: August 4, 2021

By: Oliver Lord, Head of Policy and Campaigns, and Greg Slater, Senior Data Analyst

By incentivising cleaner vehicles, Clean Air Zones are a critical tool for improving air quality and addressing pollution from transport. Clean Air Zones are taking off across the UK – London, Bath and Birmingham have all introduced their own zones, and Manchester and Bristol are set to launch one in 2022.

Although these zones are deployed locally, our new data analysis reveals how the true ‘reach’ of Clean Air Zones goes far beyond their boundary – likely bringing air quality benefits to millions of people in London and across the country.

Clean Air Zones drive change

Clean Air Zones encourage cleaner vehicles by charging older, more polluting vehicles to enter the zones, often located in busy city centres.

In 2019 London launched its first Clean Air Zone for nitrogen dioxide (NO2) – known as the Ultra Low Emission Zone (ULEZ), which requires cleaner emissions standards for vehicles driving through central London. When looking at compliance rates, it’s easy to see how the ULEZ spurred an acceleration of cleaner vehicles. In February 2017, nearly 40% of all vehicles driving in what would become the ULEZ met the emissions standards. By the time the ULEZ debuted roughly two years later, that number had jumped to 73%.

Whilst the success of the central London ULEZ has been widely reported, it is less known that in March 2021 nearly the entire capital became an NO2 Clean Air Zone for heavy duty vehicles. That means all lorries, buses and coaches driving in Greater London must meet emissions standards or pay a fee. By the end of 2020, an average of more than 92% of heavy duty vehicles met these standards – an indication of how the industry was shifting to prepare for the restrictions.

Analysing the ‘reach’

Although the emission standards are for vehicles driving inside the Clean Air Zone, we suspected that most journeys don’t remain inside the zone – delivering health and clean air benefits beyond the boundaries.

To examine the ‘reach’ of Greater London’s Clean Air Zone for heavy duty vehicles, we analysed a dataset produced by INRIX[1] that represents trips in a sample week. Since the pandemic has been hugely disruptive since March 2020, we looked at a week from September 2019.

By focusing on trips that passed through Greater London’s Clean Air Zone, we found that heavy duty vehicles drove further outside of the zone than within – on average twice as much distance. The map below reveals how – in just one week – large vehicles that were subject to the emissions standards were consistently driving many kilometres outside of London.

We also wanted to understand how many people these vehicle journeys were potentially reaching. Again looking at heavy duty vehicles crossing through Greater London’s Clean Air Zone, we found that they passed through nearly 95% of major towns and cities in England and Wales, which together have a combined population of 18 million people.

This analysis reveals how people living and working outside Greater London’s Clean Air Zone, even as far as Cardiff and Stoke-on-Trent, also benefit from the cleaner vehicles and reduced emissions brought about by the zone. As a result, city-level policy and the introduction of Clean Air Zones can benefit the health of people throughout the UK.

[1]Data was procured from INRIX. INRIX has no affiliation with the analysis or results.

Also posted in Government Official/Policymaker / Comments are closed

As UK workers return to offices, here are tips for building managers to prevent a rise in energy costs and air pollution

By Elizabeth Fonseca / Published: July 26, 2021

Following COVID-19 lockdown measures, many people went from working in offices to being unemployed or furloughed or working from home. We don’t yet know what future working behaviour looks like in the UK, but there are strong indications that many people will continue to work from home, even if there are no longer pandemic-related concerns.

New research by Future Climate for Environmental Defense Fund Europe examines how this shift could impact air pollution from heating, cooling and powering homes and offices, offering recommendations for how offices can keep emissions from rising as workers return.

Pollution from homes and offices

The pandemic has laid bare one of the by-products of modern living: the air pollution created by our day-to-day activities. Air pollution has a detrimental impact on health and is attributable to the early death of thousands of people in the UK.

Much has been said about how the lockdown-related reduction in traffic and congestion in UK towns and cities led to lower levels of nitrogen dioxide (NO2) pollution. We have not heard as much about the pollution that comes from buildings – namely air pollution created by the way we heat and power our homes and businesses.

Across the UK, NO2 pollution from heating and powering buildings is one of the main sources of air pollution alongside road transport, manufacturing and construction. Proportions vary depending on where you are in the country and in some areas building emissions are the main source. For example, in central London buildings are the largest source of NO2 emissions – 10% higher than emissions from road transport.

An increase in home working

Data reveals that those working from home in the UK went up from 6% in January 2020 to 41% in April. Although many people were no longer going into offices, office energy consumption shrank by only 16% during that time.

With more people at home, the use of boilers in domestic settings also increases, resulting in higher NO2 emissions from residential buildings. The research by Future Climate estimates that NO2 pollution from the average home could increase by 3-5% on average. In London, where there is a higher proportion of home workers, the increase could be as much as 7%, which could result in higher gas bills as well.

Returning to the office

As restrictions ease and those of us who have been unable to work or have been restricted to working from home return to offices, people are looking at how we can do so safely.

Ventilation guidance – intended to make buildings safer to reduce the chance of virus transmission – could lead to a rise in energy usage if not managed well and, in turn, a rise in pollution. For example, the guidance advises facility managers to avoid energy-saving settings and to run ventilation units two hours before office use. Carbon Intelligence, sustainability experts that help companies move toward zero-carbon, estimates that these sorts of measures could increase energy demand in offices by 70-90%.

Additionally, since office energy consumption only went down slightly during lockdown measures, it is likely consumption will return to normal levels or higher – even before you consider the ventilation guidance.

Carbon Intelligence highlights short-term recommendations for facility managers to reduce heat and energy needs, operating costs and pollution, including:

  • Ensure that scheduling of heating and ventilation systems match the building’s occupancy, e.g. reducing operation during out-of-office hours.
  • Ensure that boiler combustion systems are calibrated to maximise efficiency at low firing rates during times of reduced demand.
  • In less occupied areas, consider providing comfort heating with standalone units (e.g. radiant heaters or fans) to avoid the need for central heating/cooling plant operation.

A healthier future

With many offices buildings still not back at full occupancy, this could also be a good time to think more long-term and invest in low-pollution heating systems. Heat-pumps, geo-thermal energy and solar collectors are all supported by the government’s non-domestic renewable heat incentive and have zero local emissions.

In the recovery from COVID-19, everyone wants safe ventilation and cleaner air to stay healthy. Changing dynamics likely mean more people working from home in the UK, while offices use the same or more heat and power even with fewer people. By taking short and longer-term measures to prevent a rise in air pollution, building and facilities managers can help protect people’s health.

Also posted in Business, Corporate Sustainability Professional / Comments are closed

London’s major roads are putting children at risk of developing asthma

By Oliver Lord / Published: May 4, 2021

Greg Slater, Senior Data Analyst, and Oliver Lord, Head of Policy and Campaigns

The pollution and health impacts from London’s busiest roads – the Red Routes – go far beyond the streets themselves.

As a result of the nitrogen dioxide (NO2) that comes solely from vehicle pollution on the Red Routes, our new analysis estimates 9% of the city’s children may be living in an area where they are at a significantly higher risk of developing asthma. The analysis shows the area of increased asthma risk from Red Route pollution is seven times the size of the roads themselves.

Londoners don’t have to live directly on the major roads to experience the increased risk from their pollution. The capital needs a new vision for the city’s most polluted roads, including a comprehensive traffic-reduction plan that reduces health inequities.

Transport pollution and asthma

Our previous analysis shows how the Red Routes have far higher levels of NO2 pollution than the average thoroughfare.

To examine this in more detail and shed light on the health burden for local communities, we looked at a new modelled dataset produced by Cambridge Environmental Research Consultants (CERC) as part of the Breathe London pilot project that isolates the vehicle NO2 pollution from the Red Routes and shows where this pollution travels in the air.

In recent years, there has been building evidence of an association between exposure to traffic-related air pollution and the development of childhood asthma. In their review of research into this topic, Khreis et al (2017) found that the risk of new paediatric asthma cases increased by 5% with every 4 µg/m3 of NO2 air pollution.

We applied these findings to the modelled dataset of Red Route pollution and found levels of 4 µg/m3 NO2 and higher – just from the Red Routes – covers an area seven times bigger than that of the roads themselves. The map below displays in black where the Red Routes alone are adding at least 4 µg/m3 of extra NO2 pollution, which could increase the risk of children developing asthma by at least 5%.

We estimate 9% of London children live in the area with at least 4 µg/m3 of extra NO2 pollution from the Red Routes. Our estimates indicate these children have a significantly increased risk of developing asthma unless action is taken to reduce vehicle-related pollution on the Red Routes. This is in addition to existing asthma cases, which can be aggravated by elevated pollution levels. The map also shows levels of NO2 at or greater than 2 µg/m3, which can carry health risks as well.

Zooming in to a more local level, the map below shows the north section of the Red Route Old Kent Road and the surrounding area. The colours demonstrate how the pollution spreads beyond the road boundaries, with dark grey representing at least 4 µg/m3 of NO2 pollution from the Red Routes. Here we see the model suggests areas close to the road are all in dark grey. Residential areas much further away are also affected by Red Route pollution.

And that’s just a small slice of air pollution that London children are likely exposed to. We have looked at the Red Routes in isolation to demonstrate how pollution from major roads travels in the city. However, there are of course other roads and pollution sources, as well as air pollutants associated with traffic emissions like fine particulate matter (PM2.5) that must also be accounted for a complete picture of the health impacts.

London needs action now to protect young lungs. The next Mayor of London should commit to a bold vision and urgent action plan to address the volume of vehicles on the Red Routes and to assess if the network is still fit for purpose.

Please see here for the methods behind this data analysis.

Further detail on the health impacts of the Red Routes can be found in our paper with Centric Lab, Rethinking London’s Red Routes: From red to green. You can also watch a relevant discussion here, which took place at a Centre for London webinar with health and transport experts. 

Also posted in Health, Public Health/Environmental Official / Comments are closed

London’s major roads are noisy, polluted and outdated. It’s time to make the Red Routes healthier and more equitable.

By EDF Web Team / Published: March 31, 2021

Oliver Lord, Head of Policy and Campaigns

London’s major roads – the Red Routes – cut across the capital and carry up to a third of traffic on a typical day. Like in many global cities, these busy, outdated roads create air pollution and environmental stressors that harm people’s health in different ways.

A new discussion paper from Environmental Defense Fund Europe and Centric Lab examines health inequities along the Red Routes and highlights why now is the time for a new, healthier vision for London’s major roads.

Prioritising motor traffic

A swathe of regulations and investment, or lack there of, over a long period of time have prioritised motor traffic in London. In the 1990s, the Government introduced its ‘Red Routes’ policy to designate ’clearways’ in the capital on which through traffic movements would gain greater priority over local journeys. The Red Routes – also known as the Transport for London road network (TLRN) – cut across the capital and carry up to a third of traffic on a typical day.

The prioritisation of motor traffic significantly impacts London’s environment and creates health inequities in the city. Motor vehicle dependency remains high amongst residents and the number of miles driven by commercial vans has risen exponentially in recent years. Moreover, the Red Routes network was established in a time mostly unrecognisable today – when diesel did not have a prominent use, estimates of how the city would grow were more conservative and e-commerce deliveries were unheard of.

Air pollution and health

Pollution Zone sign by Choked Up

Londoners living, working, visiting and going to school near to a busy road are exposed to far greater levels of air pollution than elsewhere in the capital. This is a particular case for the Red Routes. According to new modelled data by Cambridge Environmental Research Consultants as part of the Breathe London pilot project, in comparison to an average road in London levels of nitrogen dioxide (NO2) pollution are 57% higher and levels of fine particulate matter (PM2.5) are 35% higher on these roads. The Red Routes will also likely be some of the last areas in the UK to meet air quality thresholds as recommended by the World Health Organization.

Ruth Fitzharris, a London mother of a young son, has felt these dangerous impacts first-hand. In the past few years her son had 12 asthma attacks, two of them life-threatening. Ruth says she was informed by the head of a severe asthmatic clinic that air pollution was a significant contributory factor to her son’s condition. Additionally, her consultant pediatrician with specialism in respiratory medicine advised her to avoid main roads when possible.

Health assessment on Red Routes

Data analysis is needed to better understand the health impacts of the Red Routes and to identify who is at greatest risk. Centric Lab undertook a health assessment of the Red Routes network – the findings are presented in the discussion paper, alongside a data matrix available for download.

The health impacts of transport-related air pollution are multifactorial and systemic. To understand the full extent of how air pollution impacts a person’s life, Centric Lab considered proximity to pollution sources alongside other pollution types (e.g., noise and light), as well as intervening social and behavioural stressors. Examples of these stressors include feeling physiologically safe, legibility and socio-economic differences.

The health assessment brings to light people’s lived experience along the Red Routes. For example, it identified how the A12 between Poplar and Bromley By Bow is a particular concern for the neurodiverse community (e.g., people on the autism spectrum or with dyslexia), as air pollution impacts are compounded by complex, disorganised and noisy environments. Similarly, the A13 between Whitechapel and Limehouse can be overbearing for children owing to environmental stressors and high levels of air pollution affecting their early stages of development. The assessment concluded all parts of the Red Routes are a priority for intervention and action should be taken to make them significantly healthier and safer.

Time for change

As the capital strives for cleaner air and considers a firm action plan to decarbonise the city, data suggests the Red Routes policy is ripe for a review. Red Routes continue to be designated primarily areas for motor movement, conflicting with the growing number of people who live and conduct daily activities by these roads.

London is also at risk of being left behind in a global movement to transform polluted arterial roads in cities. Examples include transformation projects in Seoul, Barcelona and Paris, where major thoroughfares have either been repurposed or demolished to reduce the dominance of motor vehicles. Policymakers must come together to assess whether the Red Routes are still fit for purpose, so London can become a healthier and more equitable city.

You can read the full discussion paper here. You can watch a relevant discussion here, which took place at a Centre for London webinar with health and transport experts. 

Also posted in Environmental Justice, Health / Comments are closed

The Breathe London Blueprint is here to guide your city’s monitoring project and inspire clean air action.

By Elizabeth Fonseca / Published: February 9, 2021

A key question for any city considering using lower-cost sensors or mobile monitoring to measure air pollution is, “Can they provide reliable data and insights?”

The short answer is yes and more, as we describe in our Breathe London Blueprint. The Blueprint is a guide that provides essential lessons for cities interested in using hyperlocal monitoring to turn data into clean air action.

The pilot project

For two years we managed the Breathe London pilot project, an ambitious, collaborative effort to map and measure air pollution across the city.

With more than 100 lower-cost sensor pods and specially-equipped Google Street View cars, the pilot complemented and expanded upon London’s existing monitoring networks. The city’s existing regulatory network also provided an excellent opportunity to study the performance of lower-cost sensors and mobile monitoring to determine their reliability and accuracy.

Replicating best practices

Not all cities will have the resources that were available to us in London. That’s why we created the Blueprint guide to share key lessons and help cities replicate best practices, regardless of their starting place or resource level.

We provide guidance to help you get started, including understanding your city’s unique air quality landscape and building your team.

Once you’ve got a better idea of the existing landscape – and you see where data gaps exist – you can set clear goals and design a plan to achieve them.

Achieving your goals

The Breathe London pilot used hyperlocal monitoring to:

  1. Identify pollution hotspots,
  2. Measure the impact of an air quality intervention and
  3. Raise public awareness.

The Blueprint guide explains the approach we took on these three goals and what we found in the process.

Based on what we learned in Breathe London, we include tips for how you can get started on each goal – even if you don’t have as many monitors as we did.

Digging deeper

The Blueprint guide is complemented by the comprehensive technical report, which was written by the entire project consortium and provides a behind-the-scenes look at the practical details and methodology we used.

For anyone interested in digging deeper on the project specifics or the scientific learnings, the technical report is full of detailed scientific information. Topics include quality assurance and control, as well as how the consortium used a novel network-based calibration method.

Looking ahead

We hope the guide provides valuable lessons learned from Breathe London and serves as a blueprint for how to do something similar in your city, regardless of your starting point. Our London insights are already helping our Global Clean Air efforts, such as the work we’re undertaking with Mexico City to scope and shape a hyperlocal monitoring network.

By keeping a spotlight on the threat of air pollution to our health and well-being, data from hyperlocal monitoring is increasingly becoming a viable option to inform better, higher-impact clean air solutions.

To receive news and updates like this, please sign up for our Global Clean Air newsletter.

Image by ZDRAVKO BATALIC.

 

Also posted in Health / Comments are closed

Breathe London Data Reveals Big Drops In NO2 Pollution During Commuting Hours

By Catherine Ittner / Published: October 19, 2020

London businesses are starting to reopen and some nonessential workers, who have been working from home, are considering going back into their offices. But what impact might this have on air quality?

During the lockdown, air quality data from Breathe London shows that harmful nitrogen dioxide (NO2) pollution went down significantly during commute times – 25% in the morning and 34% in the evening.

To help maintain these lower levels of pollution as shops and offices begin to reopen, businesses should allow more flexible ways of working. A new survey confirms it’s what people want.

BL weekday covid

Less pollution during commute times

Before the lockdown, many people across the city followed similar schedules on weekdays. As a result, the Breathe London network of air pollution sensors often saw daily dips and peaks of NO2 – a gas produced by fossil-fuel combustion that is associated with heart and lung-related health impacts.

In the pre-lockdown patterns, the lowest levels of this pollution measured was in the wee hours of the morning (around 3-4 am), when most people are sleeping. After they wake up and start moving to school and work, many in their fossil-fuel powered vehicles, the monitors saw a pronounced pollution increase. This falls midday, but pollution rises again in the evening to a second spike as folks return to their homes.

After confinement measures went into place, Breathe London data shows that air pollution significantly decreased across the city, including in residential areas, indicating there have been benefits to Londoners’ health even away from busy roads.

To get a better sense of how lockdown and many people working from home was impacting air quality, we then zoomed in on weekday commuting hours. Across Greater London, NO2 pollution decreased around 25% during the morning commute (8-11am) and 34% in the evening (5-8pm). These pollution reductions were even greater in the city centre, where many businesses are located – 31% and 37% respectively in the Ultra Low Emission Zone.

More work flexibility and clean air action

As lockdown eases, people across the UK want more flexible working options and action to lower air pollution.

That’s the gist of a new survey, commissioned by charity Global Action Plan on behalf of Business Clean Air Taskforce, which finds that:

  • 87% of those currently working from home would like to continue to do so to some degree.
  • 72% of the public believe clean air is more important now because coronavirus can affect people’s lungs.
  • 74% want businesses to do more to improve air quality in the recovery.

Not everyone can work from home, so it’s important businesses provide the option for those who can – leaving the roads and public transport available for essential workers to travel safely.

Build back better

Data helps us understand how pollution changes across the city, and Breathe London data shows the confinement measures have helped lessen the pollution peaks typically associated with commuting.

To protect public health and prevent the return of higher pre-lockdown pollution levels, UK employers should build back better and give people what they want by offering more flexible work options.

For more information on how pollution levels changed since confinement measures went into place, please see the full Breathe London analysis.

This was originally posted to EDF Europe.

Also posted in Monitoring, UK / Authors: / Comments are closed

How we used machine learning to get better estimate of London’s NO2 pollution reduction

By Greg Slater and Dan Peters / Published: October 5, 2020

A new analysis for UK Clean Air Day from Environmental Defense Fund Europe (EDF Europe) finds nitrogen dioxide (NO2) pollution was 40% lower than expected across London during the initial COVID-19 lockdown.

But how do we know about pollution that didn’t happen? We used a machine learning model to predict what the concentration of NO2 would have been if lockdown restrictions had not come into effect. Here’s how it works.

Removing the weather impact

Meteorology and seasonal patterns have a big impact on air quality, which needs to be taken into account when measuring changes in pollution. For example, a windy day could improve air quality by dispersing pollutants that might have otherwise accumulated locally. Meteorological and seasonal variations like this make it difficult to directly compare one period to another – are changes in pollution due to a policy intervention or behaviour change, or is it just the weather?

We wanted to isolate the impact of lockdown measures on London’s NO2 pollution, which is produced from fossil fuels and is associated with heart and lung-related health impacts.

Using open-source tools developed by researchers at the University of York (Grange, 2020), and data from over 100 regulatory air quality monitors, we built a machine learning model to help us do this. London’s long-running monitoring network provides years’ worth of historic pollution data, which is used to train and test the model, alongside a series of meteorological and temporal variables.

We can then use this model – with time and weather information from lockdown dates – to predict the pollution levels we would have expected to see had lockdown measures not occurred. These predictions mirror seasonal and meteorological changes in observed pollution levels much more closely than an historical average, for example, which may vary due to different weather during that period.

As a result, with this method the difference between expected and observed levels can be more directly attributed to the impact of lockdown restrictions rather than random weather variations.

London lockdown expected vs observed chart

40% less pollution

The figure above shows a comparison between average expected and observed NO2 concentrations. The gap between what we expected to see and what we actually saw increases dramatically after 16th March, when social distancing was strongly advised. The figure shows the close alignment of trends between expected and observed levels, illustrating how both are similarly influenced by meteorological effects during the period.

Overall, we found a 40% difference from mid-March to mid-June 2020 – i.e. NO2 pollution levels were 40% less than what the model predicted during lockdown. This is the average change across London’s different monitoring site types, including those close to roads (kerbside and roadside) and farther away from busy streets (urban background and suburban).

Changes in meteorology over time typically complicate air quality intervention analysis, but a machine learning method like this allows us to better isolate changes associated with interventions, like lockdown measures. This method has been used successfully in other recent air quality research – for example, Grange and Carslaw (2019) – and we will continue to use cutting-edge methods like this to better understand how London’s pollution levels are changing.

This analysis complements our previous lockdown assessment using data from the Breathe London monitoring network. We used data from the regulatory monitors here rather than Breathe London because training the model requires a longer historical record.

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This was originally posted to EDF Europe.

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