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Trends - Air Quality Indicators

Modelled Scenarios

The images below show maps of predicted Welsh PM10 and NO2 concentration in 2010 and 2020. Baseline pollutant concentrations are lower than illustrated in Section 5 and decline further by 2020. These maps incorporate the impact of currently agreed national and international policies on air quality, as derived from emission inventory projections.

The results for a core package of measures known collectively as 'combined measure R' are illustrated here. This includes three components:

  • Measures to reduce NOx and PM10 emissions from cars and light good vehicles (Euro 5 and 6) and heavy-duty vehicles (Euro VI).
  • A programme of incentives to increase the penetration of low emission vehicles into the national vehicle fleet
  • Measures to reduce SO2 and NOx emissions from international shipping through the International Maritime Organisation.

Measure R reduces concentrations in 2010 but the impact is greater in 2020. This is because the introduction of new vehicles with lower emissions takes several years to substantially replace the fleet of older vehicles on the road. Further key results for Wales are summarised here:

The impact of the measures has been examined in terms of the reduction of the number of exceedences of air quality objectives for PM10. In Table 1, we include results from the maps of background concentrations illustrated below.

Population-weighted annual mean concentrations have been calculated; these represent the average pollution levels experienced by the population. The health benefits of the measures were then estimated by applying dose response functions derived from epidemiological studies. In Table 2, the resulting health benefits are quantified in terms of both hospital admissions and changes in life expectancy associated with PM10. It is clear that he impact of PM on life expectancy dominates the cost/benefit analysis in Wales and, indeed, throughout the UK.

Table 1. Percentage of road length & population in Wales exceeding air objectives
PM10 provisional annual mean objective for 2010 of 20 µg m-3

Metric/year 2010 baseline 2010 measure R 2015 baseline 2015 measure R 2020 baseline 2020 measure R
Road Length 52.6 44.4 30.2 14.5 22.0 5.5
Population 12.4 9.7 6.3 3.6 4.8 2.2

Table 2. Summary of health benefits for measure R, 2020 for PM10 in Wales*

Respiratory hospital admissions 11
Cardiovascular hospital admissions 11
Life years gained 69,000 - 132,000

*Population followed for 100 years. Range represents different assumptions concerning the time lag between changes in concentration and impact.

Click on the image below to open a larger version in a new window.

Map showing future NO<sub>2</sub> modelled scenarios
Map showing future PM<sub>10</sub> modelled scenarios