ANNEX II U.K. Determination of requirements for assessment of concentrations of sulphur dioxide, nitrogen dioxide and oxides of nitrogen, particulate matter (PM₁₀ and PM_2,5), lead, benzene and carbon monoxide in ambient air within a zone or agglomeration

A. Upper and lower assessment thresholds U.K.

The following upper and lower assessment thresholds will apply: U.K.

1. Sulphur dioxide U.K.

	Health protection	Vegetation 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 critical level (12 μg/m3)
Lower assessment threshold	40 % of 24-hour limit value (50 μg/m3, not to be exceeded more than three times in any calendar year)	40 % of winter critical level (8 μg/m3)

2. Nitrogen dioxide and oxides of nitrogen U.K.

	Hourly limit value for the protection of human health (NO2)	Annual limit value for the protection of human health (NO2)	Annual critical level for the protection of vegetation and natural ecosystems (NOx)
Upper assessment threshold	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 critical level (24 μg/m3)
Lower assessment threshold	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 critical level (19,5 μg/m3)

3. Particulate matter (PM₁₀/PM_2,5) U.K.

a The upper assessment threshold and the lower assessment threshold for PM2,5 do not apply to the measurements to assess compliance with the PM2,5 exposure reduction target for the protection of human health.
	24-hour average PM10	Annual average PM10	Annual average PM2,5 a
Upper assessment threshold	70 % of limit value (35 μg/m3, not to be exceeded more than 35 times in any calendar year)	70 % of limit value (28 μg/m3)	70 % of limit value (17 μg/m3)
Lower assessment threshold	50 % of limit value (25 μg/m3, not to be exceeded more than 35 times in any calendar year)	50 % of limit value (20 μg/m3)	50 % of limit value (12 μg/m3)

4. Lead U.K.

	Annual average
Upper assessment threshold	70 % of limit value (0,35 μg/m3)
Lower assessment threshold	50 % of limit value (0,25 μg/m3)

5. Benzene U.K.

	Annual average
Upper assessment threshold	70 % of limit value (3,5 μg/m3)
Lower assessment threshold	40 % of limit value (2 μg/m3)

6. Carbon monoxide U.K.

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