# The Air Quality Standards (Wales) Regulations 2007, Part 1: Group A pollutants: human health-based limit values and alert thresholds


Population of zone (thousands)
If concentrations exceed the upper assessment threshold
If maximum concentrations are between the upper and lower assessment thresholds
For nitrogen dioxide and sulphur dioxide in agglomerations where maximum concentrations are below the lower assessment thresholds
(1) For NO2 and PM10 to include at least one urban-background station and one traffic-orientated station; this requirement also applies to benzene and carbon monoxide provided that it does not increase the number of sampling points.
0—249
1
1
not applicable
250—499
2
1
1
500—749
2
1
1
750—999
3
1
1
1,000—1,499
4
2
1
1,500—1,999
5
2
1
2,000—2,749
6
3
2
2,750—3,749
7
3
2
3,750—4,749
8
4
2
4,750—5,999
9
4
2
6,000 or more
10
5
3

---
Source: https://www.legislation.gov.uk/wsi/2007/717/schedule/6/part/1 (the official version)
Page: https://openlegislation.uk/air-quality-standards-wales-regulations-2007/schedule-6/part-1
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.