# The Air Quality Limit Values (Wales) Regulations 2002, Paragraph

Extent: E+W

The following upper and lower assessment thresholds will apply:
SULPHUR DIOXIDE
(a)
Health protection
Ecosystem protection
Upper assessment threshold
60% of 24-hour limit value (75μg/m3, not to be exceeded more than 3 times in any calendar year)
60% of winter limit value (12μg/m3)
Lower assessment threshold
40% of 24-hour limit value (50μg/m3), not to be exceeded more than 3 times in any calendar year)
40% of winter limit value (8μg/m3)
NITROGEN DIOXIDE AND OXIDES OF NITROGEN
(b)
Hourly limit value for the protection of human health (NO2)
Annual limit value for the protection of human health (NO2)
Annual limit value for the protection of vegetation (NOx)
Upper assessment value
70% of limit value (140μg/m3, not to be exceeded more than 18 times in any calendar year)
80% of limit value (32μg/m3)
80% of limit value (24μg/m3)
Lower assessment value
50% of limit value (100μg/m3, not to be exceeded more than 18 times in any calendar year).
65% of limit value (26μg/m3)
65% of limit value (19.5μg/m3)
PARTICULATE MATTER
(c)
24-hour average
Annual average
Upper assessment threshold
60% of limit value (30μg/m3, not to be exceeded more than seven times in any calendar year).
70% of limit value (14μg/m3)
Lower assessment threshold
40% of limit value (20μg/m3, not to be exceeded more than seven times in any calendar year).
50% of limit value (10μg/m3)
LEAD
(d)
Annual average
Upper assessment threshold
70% of limit value (0.35μg/m3)
Lower assessment threshold
50% of limit value (0.25μg/m3)
BENZENE
(e)
Annual average
Upper assessment threshold
70% of limit value (3.5μg/m3)
Lower assessment threshold
40% of limit value (2μg/m3)
CARBON monoxide
(f)
Eight-hour average
Upper assessment threshold
70% of limit value (7 mg/m3)
Lower assessment threshold
50% of limit value (5 mg/m3)

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Source: https://www.legislation.gov.uk/wsi/2002/3183/schedule/2/part/I/paragraph/wrapper3n1 (the official version)
Page: https://openlegislation.uk/air-quality-limit-values-wales-regulations-2002/schedule-2/part-I/paragraph-wrapper3n1
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.