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.
Air pollution data
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.
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.