Climatologically / Topographical peculiarities
Winds in the city are predominately from a west and southwesterly direction; hence the motorway and radial routes to the south and west of the city
contribute to the city centre's air quality.
Main sources of emissions
Cars are the main form of transport into the city centre and congestion is an increasing problem for the city. Traffic is the main contributor of
emissions of CO (88.6%), PM10 (54.2%) and NOx (50.2%) for the city. The main problems for air quality are roadside locations in the city centre and along
main radial routes into the city. These areas of the city have been designated Air Quality Management Areas (AQMA).
Air Quality situation with regard to main pollutants NO2, PM10, O3, SO2, CO
The dominant source of nitrogen dioxide is motor traffic; accounting for 95% of measured levels, 60% of this is attributed to heavy vehicles.
Even at non-roadside locations, the contribution of road traffic to the ambient levels of NO2 is dominant.
Current measuring and modelling suggests that PM10 levels in Leicester did not exceed 40µg/m3 in 2004.
Ozone incidents regularly occur in Leicester in the summer months but because of its secondary and Tran-boundary nature, it is unlikely that any
cost-effective action can be taken at local level to affect the excess ozone levels in Leicester.
Leicester has in its entirety been a Smoke Control Area for over 20 years and as a result sulphur dioxide levels have fallen by a factor of around
10 since the early 1960's. In addition, there has been the progressive reduction of the statutory maximum sulphur content of diesel fuel.
Monitored carbon monoxide levels in Leicester are well below the 10mg/m3 objective. The main source of carbon monoxide in the UK is road transport,
which accounts for around 75% of total emissions, 71% being derived from petrol vehicles.
Are limit values met or exceeded
In 2003 CO levels in the city are well below the 10mg/m3 objective parameters. Similarly, the air quality objectives for SO2 and PM10 will be
achieved in Leicester. The only exceedences of National Air Quality Objectives in Central Leicestershire are due to the level of nitrogen dioxide in
close proximity to the major road network; the dominant source being vehicle exhaust emission. Both the annual mean objective of 40µg/m3 and the 1-hour
objective of 200µg/m3 are likely to be exceeded. For O3 there were 38 exceedences of >1000 µg/m3 daily maximum 8 hour running mean in 2003 and similar
exceedences in 2004.