Executive Summary

The UK National Air Quality Strategy (NAQS) gives the following objective for PM₁₀ to be achieved by the end of 2005:

• 24-hour running mean of 50 mgm-3, measured as the 99th percentile.
  

The European Union 'Daughter Directive' gives the following limit values for PM₁₀:

• Stage 1, to be achieved by 1 January 2005: annual mean limit value of 40 mgm-3 and 24-hour limit value of 50mgm-3, not to be exceeded more than 35 times a year (approximately equivalent to a 90th percentile of 50mgm-3).
  
• Stage 2, to be achieved by 1 January 2010: annual mean limit value of 20 mgm-3 and 24-hour limit value of 50mgm-3, not to be exceeded more than 7 times a year (approximately equivalent to a 98th percentile of 50mgm-3).
  

The stage 2 limit values are indicative and will be reviewed in the light of information on health and environmental effects, technical feasibility and experience in the application of Stage 1 limit values in Member States.

The source apportionment of airborne particulate matter in the United Kingdom has recently been comprehensively reviewed by the Airborne Particle Expert Group in their first report. A new receptor modelling technique has been developed which has given new quantitative insights into the sources of PM in the UK. The receptor modelling technique was extended to provide forecasts of concentrations for comparison with the NAQS objective and EU 'Daughter Directive' limit values for PM₁₀. Projections of PM₁₀ concentrations for 2005 were calculated by multiplying the individual contributions to daily particle concentrations by emissions reduction factors derived from model studies. The forecasts of emissions changes presented within the APEG report were for a 'business as usual' scenario, defined as the likely impact of current national and international policies on current emissions.

This report describes the further development of these receptor modelling and forecasting methods that has been carried out by air quality experts at AEA Technology NETCEN on behalf of the Department of the Environment Transport and the regions.

The projections that have been calculated for a business as usual scenario indicate that significant exceedances of the National Air Quality Strategy objective for PM₁₀ are likely in 2005. Projected 99th percentiles are well in excess of 50 mgm-3 for urban background monitoring site locations in major cities and concentrations are also likely to be in excess of the objective in many smaller urban areas, particularly for years with elevated secondary particle concentrations, such as 1996.

The picture is similar for the EU 'Daughter Directive' indicative Stage 2 limit values for 2009, with exceedances in many areas likely with the business as usual scenario. Projected concentrations in 2004 are expected to be lower than the EU 'Daughter Directive' Stage 1 limit values at most urban background locations, with the possible exception of central London, particularly for years such as 1996.

Concentrations at the roadside are expected to be higher than at nearby background locations. Concentrations higher than the EU Stage 1 limit value are therefore expected at the roadside of heavily trafficked roads in urban areas in 2004. Concentrations at sites with significant industrial source contributions to measured ambient PM₁₀ concentrations are also expected to be at risk of exceeding this limit value.