We check air pollution by measuring concentrations of nitrogen dioxide and PM10 and PM2.5 particulate matter. PM10 and PM2.5 are particles smaller than 10 and 2.5 microns in diameter, respectively.
We have continuous monitors on Gonville Place, Montague Road, Newmarket Road, Parker Street and Regent Street. These calculate hourly average pollution concentrations.
There are also about 70 ‘diffusion tubes’ recording nitrogen dioxide concentrations around the city. These do not show day-to-day fluctuations related to traffic levels or weather conditions. But they give us a good indication of concentrations in the area and help us notice any changing trends.
You can see a map of the monitoring stations at the bottom of this page.
UK-Air provides data for the continuous monitor on Regent Street. Air Quality England provides data for the other 4 continuous monitors.
Air pollution data
We do not consider air-quality data measured in 2022 to be fully representative of post-Covid 19 levels. There was a significant increase in pollutant levels in 2022 compared with levels measured in 2021 and a continued rise is expected in 2023 – this is based on an initial analysis of traffic data in early 2023. All air-quality assessments should continue to use 2019 data as a baseline for a further year, after which we can reassess and might have a fuller picture of ‘new normal’ levels post-Covid 19.
Ricardo AEAT have ratified these data. An appropriate correction factor has been applied to the PM10 data where required.
Defra says an annual average from diffusion tubes below 60µg/m3 is a good sign that short-term nitrogen dioxide targets are being met. Levels in Cambridge are below this.
The diffusion tube data have been bias-adjusted.
Annual report on air quality in Cambridge
The Local Air Quality Management framework requires us to publish an annual status report. It must detail that year’s monitoring results, an assessment of findings, and measures that we have taken to improve air quality since the last report.
Air quality objectives
We are working to meet the following national targets for air quality in Cambridge:
- The annual mean concentration of nitrogen dioxide should not exceed 40µg/m3.
- The 1-hour mean concentration of nitrogen dioxide should not exceed 200µg/m3 more than 18 times per year.
- The annual mean concentration of PM10 particulate matter should not exceed 40µg/m3.
- The 24-hour mean concentration of PM10 particulate matter should not exceed 50µg/m3 more than 35 times per year.
When air pollution exceeds these concentrations, we must create an air quality management area and develop an action plan to reduce the pollution.
Air quality management
We designated the area inside the ring road as an air quality management area in 2004. This was mainly because of high levels of nitrogen dioxide caused by traffic. The area extends along some radial roads outside of the ring road.
- Air quality management area map [PDF, 3.5MB]
- Air quality action plan
- Find out more about how we are improving air quality
Air quality monitoring station maps
- Blue markers: Continuous monitors
- Green markers: Diffusion tubes
Low-cost air-quality sensors
In 2019 the government gave us grant funding to trial some low-cost air-quality sensors. We used them to monitor air quality in and around the Mill Road area, while the bridge was closed for rail-improvement work for eight weeks in the summer.
To support this work, the Smart Cambridge programme gathered data about traffic movements on Mill Road and the diversion routes.
The trial found that the low-cost sensors are a useful indicator of trends in air quality. But they are less accurate than the continuous monitors we use elsewhere to provide absolute measurements of individual pollutants.
We will continue to use the sensors to monitor trends in air quality as required on other projects.
The monitoring was part of a joint project with the county council, the Greater Cambridge Partnership and the University of Cambridge.
