The Air Quality Limit Values (Scotland) Regulations 2003 No. 428

SCHEDULE 3 UPPER AND LOWER ASSESSMENT THRESHOLDS AND EXCEEDANCES

PART I UPPER AND LOWER ASSESSMENT THRESHOLDS

1.1  The following upper and lower assessment thresholds will apply:–

(a) SULPHUR DIOXIDE

	Health protection	Ecosystem protection
Upper assessment threshold	60% of 24-hour limit value (75 μg/m3), not to be exceeded more than 3 times in any calendar year	60% of winter limit value (12 μg/m3)
Lower assessment threshold	40% of 24-hour limit value (50 μg/m3), not to be exceeded more than 3 times in any calendar year	40% of winter limit value (8 μg/m3)

(b) NITROGEN DIOXIDE AND OXIDES OF NITROGEN

	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 (140 μg/m3), not to be exceeded more than 18 times in any calendar year	80% of limit value (32 μg/m3)	80% of limit value (24 μg/m3)
Lower assessment value	50% of limit value (100 μg/m3), not to be exceeded more than 18 times in any calendar year	65% of limit value (26 μg/m3)	65% of limit value (19.5 μg/m3)

(c) PARTICULATE MATTER

	24-hour average	Annual average
Upper assessment threshold	60% of limit value (30 μg/m3), not to be exceeded more than seven times in any calendar year	70% of limit value (14 μg/m3)
Lower assessment threshold	40% of limit value (20 μg/m3), not to be exceeded more than seven times in any calendar year	50% of limit value (10 μg/m3)

(d) LEAD

	Annual average
Upper assessment threshold	70% of limit value (0.35 μg/m3)
Lower assessment threshold	50% of limit value (0.25 μg/m3)

(e) BENZENE

	Annual Average
Upper assessment threshold	70% of limit value (3.5 μg/m3)
Lower assessment threshold	40% of limit value (2 μg/m3)

(f) CARBON MONOXIDE

	Eight-hour average
Upper assessment threshold	70% of limit value (7mg/m3)
Lower assessment threshold	50% of limit value (5mg/m3)