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Show WHO Guidelines (2005*): (More Information)
*updated WHO 2021 standards coming soon

2005 Guidelines	Ozone	Nitrogen Dioxide	Sulphur Dioxide		PM2.5 Particles	PM10 Particles
Period	Running 8 hourly mean	Hourly mean	15 minute mean	24 hour mean	24 hour mean	24 hour mean
Units	µg m-3	µg m-3	µg m-3	µg m-3	µg m-3	µg m-3
Exceedance point	100	200	333	20	35	50
For pollutants with only daily limits (PM10, PM2.5, O3), we have used the same trigger system which is 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.

Air pollution levels for Tuesday 24 December 2024, 15:00-16:00GMT


Low (1-3)	Moderate (4-6)	High (7-9)	Very High (10)	Predicted	No Index	Closed

How is the Air Pollution Index calculated?

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This map shows the daily air quality index from LAQN pollution analysers. Not all analysers on the network are contacted every hour, so some sites may show 'no data'. Data have undergone automatic validity checks.

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 'Episodes' link.

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