Under the Environment Act 1995 we are required to monitor air quality in our area.
The UK Government has an Air Quality Strategy which sets out national air quality objectives. We are required to assess air quality against these objectives.
The main source of air pollution in our area is from traffic, like cars lorries buses and so on. Vehicle exhausts let out pollution like oxides of nitrogen, carbon monoxide, carbon dioxide and fine dust particles.
This can be made worse where traffic is slow moving through old narrow streets or near town centres.
The ones that can most affect our health are the nitrogen oxides like NO2 (nitrogen dioxide), and fine dust particles especially the ones which can be breathed deep into our lungs - called PM10 and PM2.5.
Monitoring air pollution
In order to check the air quality in our district, we sample air pollution at certain locations, by passive sampling.
Passive Sampling
This is where we measure NO2 (Nitrogen Dioxide). Using diffusion tubes.
These are small, clear plastic tubes which are placed on post two metres above ground at the side of a road for a month. The top of a tube has a cap which contains a steel gauze and a reactive chemical material, the bottom of the tube is open. This allows the air to contact the reactive material within the tube, and also protects the gauze from the weather.
The chemical material at the top of the tube reacts with the Nitrogen Dioxide (NO2) in the air and converts this to Nitrate (NO-3). The Nitrate is then trapped in the steel gauze. At the end of the month, all the tubes are replaced and those collected are sent to a laboratory to be examined.
At the moment we have diffusion tubes at 26 roadside locations across the district at key locations such as our schools.
The results can be viewed Essex Air Quality
If you are an air quality professional the data in the spreadsheets is raw, uncorrected data.