These statistics show how the pollutants measured at monitoring sites have fared in comparison to the UK air quality objectives.

Pollutant	Objective	Value	Achieved?

The table below sets out the government's air quality objectives for the most commonly monitored types of pollution. It is these objectives against which the results above are calculated.

Pollutant	Air Quality Objective		To be achieved by
	Concentration	Measured as
Nitrogen dioxide	200 µg m-3 not to be exceeded more than 18 times per year	1 Hour Mean	31 December 2005
	40 µg m-3	Annual mean	31 December 2005
Particles (PM10) (gravimetric)
All authorities	50 µg m-3, not to be exceeded more than 35 times per year	Daily Mean	31 December 2004
	40 µg m-3	Annual mean	31 December 2004
Particles (PM2.5) (gravimetric) *	25 µg m-3 (target)	Annual mean	2020
All authorities	15% cut in urban background exposure	Annual mean	2010 - 2020
Sulphur Dioxide	350 µg m-3, not to be exceeded more than 24 times per year	1 Hour Mean	31 December 2004
	125 µg m-3, not to be exceeded more than 3 times per year	24 Hour Mean	31 December 2004
	266 µg m-3, not to be exceeded more than 35 times per year	15 Minute Mean	31 December 2005
Ozone *	100 µg m-3 not to be exceeded more than 10 times per year	8 hourly running or hourly mean*	31 December 2005