The Air Quality Standards (Scotland) Regulations 2007

PART 1Assessment thresholds for Group A pollutants

Benzene

Annual average
Upper assessment threshold70% of limit value (3.5 μg/m3)
Lower assessment threshold40% of limit value (2 μg/m3)

Carbon monoxide

Eight-hour average
Upper assessment threshold70% of limit value (7 mg/m3)
Lower assessment threshold50% of limit value (5 mg/m3)

Lead

Annual average
Upper assessment threshold70% of limit value (0.35 μg/m3)
Lower assessment threshold50% of limit value (0.25 μg/m3)

Nitrogen dioxide (NO2) and oxides of nitrogen (NOx)

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 threshold70% of limit value (140 μg/m3), not to be exceeded more than 18 times in any calendar year80% of limit value (32 μg/m3)80% of limit value (24 μg/m3)
Lower assessment threshold50% of limit value (100 μg/m3), not to be exceeded more than 18 times in any calendar year65% of limit value (26 μg/m3)65% of limit value (19.5 μg/m3)

PM10

24-hour averageAnnual average
Upper assessment threshold60% of limit value (30 μg/m3), not to be exceeded more than 7 times in any calendar year70% of limit value (14 μg/m3)
Lower assessment threshold40% of limit value (20 μg/m3), not to be exceeded more than 7 times in any calendar year50% of limit value (10 μg/m3)

Sulphur dioxide

Health protectionEcosystem protection
Upper assessment threshold60% of 24-hour limit value (75 μg/m3), not to be exceeded more than 3 times in any calendar year60% of winter limit value (12 μg/m3)
Lower assessment threshold40% of 24-hour limit value (50 μg/m3), not to be exceeded more than 3 times in any calendar year40% of winter limit value (8 μg/m3)