Air pollution in Swedish towns and cities must decrease

Several Swedish towns and cities have problems with air pollution today, despite lower emissions. New research at SMHI shows that it may be difficult to fully achieve clean air objectives also in the future. The results confirm that it is primarily local emissions caused by road traffic that need to be restricted.

Emissions of air pollutants from road traffic have decreased both in Sweden and Europe, mainly thanks to improved cleaning and better fuels. Nevertheless, levels of air pollution are still high in many towns and cities, where they exceed EU air quality standards and national environmental objectives.

A new report from SMHI shows what is required for Sweden to achieve the EU standards and Sweden’s environmental objective for clean air. Calculations have been made for emission trends in recent years and up to the year 2020.

The research results confirm that it is emissions from Swedish road traffic that are most significant to the pollutants that cause problems in Swedish traffic environments. Emissions in Europe, which are transported to Sweden via the atmosphere, do not affect this type of pollution to any great extent.

“Swedish traffic is the predominant cause of the poor air quality in our towns and cities. Local measures will therefore be important in achieving good air quality. Consequently, we can improve our air quality in Sweden ourselves,” says Gunnar Omstedt, an air environment researcher at SMHI.

Examples of calculated extreme levels of large particulate matter, PM10, for different locations and streets. The results show levels for the years 2004 and 2020. The red line signifies European air quality standards, and the green line the Swedish environmental objective for clean air.
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Future development

The analysis encompasses calculations which show where the emissions come from. The expected future development of pollutants caused by road traffic is also reported: nitrogen dioxide, large particulate matter (known as PM10) and small particulate matter (PM2.5).

The studies into nitrogen dioxide indicate that emissions will decrease, and there are fairly good conditions for achieving the EU standards by the year 2020. There is, however, a risk that levels will remain high over the next 10 years if the percentage of diesel vehicles continues to increase.

When it comes to the large particles, PM10, there is little chance of achieving the norms and environmental objectives within the next 10 years. With these particles it is primarily road wear that causes the problems in Sweden. Measures such as lower traffic levels and less use of studded tyres are needed here.

“All in all, achieving the objectives for larger particles in Sweden appears to be a concern. With nitrogen dioxide it is also important to follow developments using air quality monitoring in street canyons,” says Stefan Andersson, an air environment researcher at SMHI.

However, the prospects look brighter for achieving the objectives for small particles, PM2.5, which are mainly transported and formed in the air over a longer period. Levels of small particulate matter in Sweden are largely dependent on emission levels in Europe.

Air quality calculations have been performed for 11 Swedish towns and cities, on streets with air problems. The calculations are made using SMHI’s models, MATCH for long-distance transport and SIMAIR for local emissions. The future calculations are based on previously developed emission scenarios, for Europe and Sweden, based on assumptions about new technology with lower emissions.

The research project has been carried out on behalf of the Swedish Environmental Protection Agency.