Introduction to Stage 1 Air Quality Assessment
Introduction to our Air Quality plans
Part IV of the Environment Act 1995 placed new responsibilities on local authorities to assess and review air quality in their areas. National standards have been set based on the recommendation of the Expert Panel on Air Quality Standards (EPAQS). These standards are now published in the National Air Quality Strategy (NAQS) along with objectives that are to be achieved by the end of the year 2005. The aim of the NAQS is to reduce the level of specified pollutants in ambient air. The standards and objectives are outlined in Table 1.
The NAQS adopts a phased approach to achieving the standards by 2005. Three stages exist which act as a filtering process to permit local authorities to comply with the strategy.
Stage 1.
Collection of information on the main sources of pollution.
Stage 2.
Measurements and computer modelling to identify areas within the authority that may exceed objectives.
To be completed by end of 1999.
Stage 3.
Detailed investigation to identify local hot spots where it is probable that objectives will not be met by 2005.
To be completed by end of 1999.
Each authority must complete stage 1. This stage is an emission inventory that identifies the major sources of pollution in an their area. If certain conditions exist the authority must progress to and complete stage 2. If stage 2 identifies further certain conditions then an authority must progress to stage 3. If after the completion of all three stages it appears that the standards are likely to be breached then an authority must declare a Air Quality Management Area (AQMA) and devise action plans to allow compliance with the standards.
Table 1 Air Quality Standards
| SUBSTANCE | AIR QUALITY OBJECTIVE LEVELS |
| Carbon Monoxide | 10 ppm or less, when expressed as a running 8 hour mean |
| Lead | 0.5 ug/m3 or less, when expressed as a annual mean |
| Benzene | 5 ppb or less, when expressed as a running annual mean |
| 1,3-Butadiene | 1 ppb or less, when expressed as a running annual mean |
| Nitrogen Dioxide | 150 ppb or less, when expressed as an hourly mean, and 21 ppb or less, when expressed as an annual mean |
| Sulphur Dioxide | 100 ppb or less, when expressed as the 99.9th percentile of 15 minute means |
| Particulate Matter (PM10) | 50 ug/m3 or less, when expressed as the 99th percentile of daily running maximum running 24 hour means |
ppb = parts per billion
ppm = parts per million
ug/m3 = micrograms per cubic metre
"Running means" are averages that are expressed over a moving rather than a fixed period.
*A percentile means the standard must be met for a percentage of time. For example a 97th percentile means the standard must not be breached for 97% of the time. This is to allow time off for events like bonfire night.
