In the City Strategy, the objective is to lower the emissions of the transport system further and also reduce the emissions harmful to health significantly. The air quality in Helsinki has improved over the last few decades, and it is fairly good at an international level. However, the annual limit of nitrogen dioxide, specified in the EU’s Air Quality Directive, is in danger of being exceeded in the city centre’s street canyons. The reason for this is the exhaust emissions from traffic, in particular diesel vehicles. Air quality is also worsened by inhalable particles, i.e. dust, especially in spring and in the vicinity of large construction sites. There is also still a risk that the limit value for street dust will be exceeded. In dense detached house areas, the air quality is decreased by small-scale burning of wood in fireplaces and sauna stoves. In the Helsinki Metropolitan Area, small particle emissions from fireplaces are even greater than those from traffic.
The purpose of the City’s Air Quality Plan is to reduce nitrogen dioxide emissions from traffic so that the emissions will fall below the annual limit as soon as possible. In addition to decreasing exhaust gas emissions, the plan’s other focus areas are street dust and small-scale burning of wood. The plan contains a total of 48 measures to be implemented in 2017–2024.
In 2020, the air quality in Helsinki was good or satisfactory most of the time. The concentrations of nitrogen dioxide (NO2) and street dust (PM10) were exceptionally low in 2020 as a result of the weather conditions and reduced amount of traffic. Small particle (PM2.5) concentrations were also slightly lower than usual. However, the air quality worsened to passable or poor in areas with busy traffic at times.
Nitrogen dioxide concentrations decreased
In total, the nitrogen dioxide concentrations in 2020 were approximately a third lower than in the last few years. No values exceeding the limit value were measured in 2020. The concentrations have decreased due to the car stock and the Helsinki Region Transport (HSL) bus fleet becoming lower-emission. The mild and windy weather conditions of winter 2020 also contributed to the decrease in exhaust gases in the city air.
Efforts to prevent street dust must be continued
The amounts of inhalable particles (PM10) were clearly below the limit values in 2020. The street dust season was easier than usual starting from early spring due to the reduced amount of traffic as well as the exceptionally warm and snowless winter.
The PM10 limit values have not been exceeded since 2006, but the WHO guideline value for street dust continues to be exceeded year after year.
Continuous efforts towards preventing street dust and developing methods to reduce it are highly important. Street dust can be reduced by mitigating the amount of traffic and promoting the use of non-studded winter tyres. In autumn 2020, Helsinki campaigned for the use of non-studded winter tyres.
Construction sites and small-scale burning of wood worsened the air quality locally
The impact of large construction sites on local particle concentrations has been measured in recent years. In 2020, measurements were carried out in Jätkäsaari. Efforts are being made to prevent dust emissions in cooperation with contractors, and new methods are being developed in the HOPE project coordinated by Helsinki, among others.
Efforts are being made to find ways to decrease emissions from small-scale burning of wood by means such as research projects in which the City is involved. Additionally, residents have been extensively provided with information on ways to influence how cleanly wood burns. The burning method and the dryness of the wood have a major effect on the formation of emissions.
Eyes on the future
In 2020, the amount of traffic decreased in Helsinki due to the coronavirus pandemic. This was also widely evident in the form of better air quality. It remains to be seen what type of permanent impact things such as increased telecommuting will have on the amount of traffic and air quality in Helsinki.
Street dust remains a challenge despite the number of low-emission cars in the car stock increasing, which is why promotion of the use of non-studded winter tyres and dust prevention will continue to be essential measures in the future. Emissions from wood-burning will continue to worsen the air quality in detached house areas in the future.