New start, old problems: Two-fifths of British schools report above average NO2 levels in 2021. London ranks top for bad air, deprived areas suffer the most.

  • Schools: The air pollution levels around 41% of British schools have higher than average NO2 levels caused by car and factory pollutants
  • Regional impact: Larger numbers British schools struggle to manage NO2 standards, London remains top ranked for worst air pollution. 
  • Economic divide: Schools in socially deprived areas are more susceptible to higher levels of air pollution 

1st September 2021, London: A new academic year starts with fresh hopes but some lingering problems persist. Chiefly, high air pollution levels around schools. Cleantech platform Airly conducted a study based on available air pollution monitoring sources which shows NO2 levels were greater than WHO acceptable levels around 41% of UK schools. 

What is NO2 or nitrogen dioxide? It is a pollutant gas which increases the risk of asthma and exacerbates the symptoms of asthma in children, reduces lung function and increases the likelihood of inflammation of the airways. The main sources of NO2 are road traffic (fuel combustion) and heavy industry.


During pandemic-related lockdowns, air quality around schools improved but over the last 12 months, it has returned to the excessive ‘normal’. The charts below illustrate the problem by timeline. Notably, NO2 levels around schools in London have the highest levels across the UK. 


Entire UK:


41% of British schools exceeded the acceptable levels of NO2 in 2021. This is an improvement from 2019 when 49% of schools across the country had exceeded the norms. The significant drop in NO2 levels during the lockdown in spring 2020 and during the following summer vacation shows the extent to which human activity can impact NO2 levels.

Pollutants such as NO2 and PM10 affect not only health but also learning ability. Several studies from recent years prove that air pollution can harm cognitive intelligence, while  other studies have proven that reducing air pollution can significantly increase the memory of young people. 

Another finding from the Airly study shows that children living in the poorest parts of the UK are more exposed to higher levels of air pollution. The analysis of the mean PM10 pollution (the most common pollutant measured) around schools in the United Kingdom showed that there is a relation between the PM10 concentrations and the IMD Score of the neighbourhood. This graph presents the relationship between IMD Score and air pollution around schools, grouped in boroughs. Selected boroughs are highlighted.

These socially deprived areas have a greater presence of air pollution for a number of factors including the concentration of older cars, dense housing populations, the lack of green urban areas, part of the industrial revolution legacy and have worse aero sanitary conditions. 

What can schools do to improve the situation?  In order to reduce air pollution near schools, it is first and foremost necessary to know what level of pollution there is in the vicinity of the school. To measure this, it is necessary to monitor the air quality outside, to measure the air quality in the vicinity of the facility on an ongoing basis and to analyse the pollution peaks in order to effectively influence their flattening. Airly launched the #LetSchoolsBreathe campaign earlier this year, the aim of which was to provide 50 air quality sensors to schools in the UK so that they could monitor the air quality in their surroundings on an ongoing basis. After six months, each school is to receive a report analysing the concentrations of No2 and PM at schools and suggestions on what steps to take to improve the situation.


The next step may be to reduce car traffic near the school, rearrange the paths to the school to minimize the risk of contamination for students, or also increase the amount of green space near the schools both at the front and backyard.

EarthSense Collaborates with WSP to Investigate Air Pollution Around London Schools

EarthSense, the air quality expert, is collaborating with professional services and consulting firm, WSP to assess the air quality around a consortium of schools in London.

EarthSense Zephyr® air quality sensors have been deployed throughout a group of schools in the City of London due to the growing concern of parents and teachers about the impact of high levels of air pollution on pupils’ long-term health. Zephyr® sensors are situated in the main reception and outdoor areas of each site to help identify and mitigate sources generating spikes in air pollution.

The project sees Zephyr® air quality sensors recording concentrations of nitrogen dioxide (NO2) and particulate matter (PM2.5) in and around each location to establish the exposure levels pupils and staff experience during school times.

Using an active sampling mechanism which takes ambient air pollution measurements every 10 seconds via an inlet, followed by releasing the sample through a separate air outlet, Zephyr® air quality sensors provide WSP project managers with real-time NO2 and PM2.5 measurements which are viewed via the EarthSense web app, MyAir®. The web app provides users with quantified information about measured air pollutant concentrations, which can be viewed in an interactive map, downloaded, and analysed. Using this data, those involved in the project can easily identify spikes and trends in air pollution levels. 

Once dangerous NO2 levels are detected, air quality data from the sensors will be used to determine the requirement for, and gauge the success of, measures to reduce pollution. Once determined, informed pollution interventions can be implemented and supporting data can be used to keep parents of pupils and staff notified about pollution levels. Schools will now be able to advise parents and pupils on actions to take to reduce their exposure to poor air quality on their journeys to and from school.

Dr Peter Walsh, Technical Director at WSP stated: “The Zephyr® sensors have proven to be the optimal device for our clients’ needs as they are unobtrusive, relatively silent monitoring devices, and require minimal manual intervention. They have provided our client with a continuous feed of both ambient and indoor air quality data, and an instantaneous data download, via MyAir®, from within a classroom environment with no disruption to the pupils or class activities.”

Commenting on the project, Managing Director at EarthSense, Tom Hall adds: “We initially started working with WSP to carry out a study on a traffic management system in the Midlands and it’s great to see our partners using our products and services across a variety of other industries impacted by air pollution.”                                                                                                                                    
Tom continues: “It’s important that we continue to work on projects like these as London experiences higher levels of pollution than anywhere else in the UK. With almost nine million people residing in the city, in conjunction with the lack of open green spaces available, emissions from the increased number of vehicles and underground transport get trapped in built-up areas and can enter the respiratory system of those nearby.”