Exhaust fumes

Exhaust fumes contain many hazardous chemicals

Helsinki air quality is most adversely affected by emissions from transport, because these emissions are released low near the breathing height. Exhaust fume concentrations are also at their highest in busy areas during peak hours, so large numbers of people are exposed.

Exhaust fumes contain gaseous and particulate impurities. The gaseous impurities include nitrogen dioxide (NO₂), nitrogen monoxide (NO), carbon monoxide (CO) and diverse volatile organic compounds (VOCs) including benzene.

Fine particles in exhaust fumes (PM_2.5) mainly consist of back coal and other organic compounds such as polycyclic aromatic hydrocarbons (PAH). The particles also contain some metallic compounds. The main source of particulate matter in transport is diesel vehicles.

Nitrogen limits exceeded in busy street canyons

The exhaust emissions from transport still cause high nitrogen dioxide (NO₂) concentrations in the busy street canyons of the inner city. In recent years, however, these concentrations have been decreasing. No excess to the annual limit of NO₂ was observed in the Helsinki Region Environmental Services Authority’s measurements in 2020.

The local large concentrations of nitrogen dioxide and exceeding the limit value are caused by car emissions, especially from diesel cars. The proportion of diesel cars started to increase quickly after the tax reform that came into force in 2008. At the time, the direct nitrogen dioxide emissions grew as a consequence of technical solutions made to reduce particle emissions.

It is estimated that the nitrogen oxide emissions of diesel cars made now and in the future will be lower also in actual traffic. This will be achieved through new kinds of testing methods and statutory testing cycles that force car manufacturers to reduce emissions.

Read: Monitoring air quality

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14.07.2021 13:09