For pollutants with only daily limits (PM10, PM2.5, O3), we have used the same trigger system
used to predict levels for the UK Daily Air Quality Index. The WHO SO2 Guideline is specified as a ten minute mean,
but our instruments are set to take 15 minute measurements. We have converted the WHO 500 ug/m3 ten minute mean into
the equivalent 366 ug/m3 15 minute mean, and are reporting to this in line with the recommendations of the UK Expert
Committee on Air Quality Standards.
Please note that the PM2.5 Guideline for the UK has been determined using the
UK average PM2.5:PM10 ratio of 0.7, as per the WHO guidance, rather than the 'global' ratio of 0.5
which is indented
for developing countries. For UK conditions this means that the daily WHO Guideline for PM2.5 is 35ug/m3.
You can find out more information about each location (monitoring site) by clicking on its dot on the map.
Once selected you can find out further information by clicking the 'Site Details' link above.
Click the 'Statistics' link above to see results from this site compared to national limit values. Past pollution episodes can be seen by clicking on the
Alternatively, click on the button below to see a graph of this week's pollution levels.