How do I use and interpret the annual air quality map?

How do I use?

The annual indicative air quality map currently shows the modelled nitrogen dioxide, fine particle and thoracic partivle concentrations from 2024 and 2025. Nitrogen dioxide mostly comes from traffic exhaust gases and fine particles from particles transported from outside the country’s borders, local traffic, and wood burning and in addition, the concentrations of thoracic particles consist largely of road dust resuspended by local traffic. 

• By default, the annual map shows the annual average.
• The colour scale on the right side of the annual map shows the numerical value of the concentration at the changing point of the colour.
• If you click on a specific location, the annual average for that particular location is shown.
• You may view the annual map from further away or close up by clicking on the plus (+) or minus (-) sign in the left top corner of the air quality map.
• The buildings become visible when you zoom in. Buildings are not visible if the map of the entire area is opened.
• In addition to the annual concentration, you can select the average concentrations for winter (December–February), spring (March–May), summer (June–August) or autumn (September–November) under ‘Whole year’. Selecting a season on the map will show the average concentration for that period.
• When the buildings are visible, clicking on a specific location will display the monthly averages for that location. In addition, you can see how concentrations vary on weekdays and weekends during the day at that location.
• You will see the average for the full year when you have selected the entire year. For example, if you have selected winter as the season, you will see the monthly values for winter and the daily variation on weekdays and weekends during the winter months.
• Under information, there is a link to these instructions and pages with tips on air quality for residents and urban planners.
• You can download the map for yourself from the button in the top corner.
• The map works best with the Chrome browser. 

How do I interpret?

On the right side of the map, there is a colour bar indicating the air quality. The colour green refers to good air quality and the closer you get to red, the poorer the air quality is. Also, the lower the concentration, the better the air quality.  

The map shows the nitrogen dioxide concentrations in exhaust gases from car traffic. If their concentrations are high, then the concentrations of fine particles caused by traffic are also elevated. 

In addition to exhaust gases, car traffic causes street dust and noise as well. 

Additionally, the map shows the concentrations of fine particles. In the Helsinki metropolitan area, the concentrations of fine particles in the outdoor air are affected by emissions from traffic and wood burning. Furthermore, a significant amount of fine particles is transported to the metropolitan area from outside the country’s borders. Due to their small size, fine particles remain in the air for a long time and can be carried by air currents for thousands of kilometers. Long-range transport accounts for more than half of the fine particle concentrations on average, even in the busy traffic areas of the metropolitan area.

The map also shows the concentrations of thoracic particles, which consist largely of road dust. They are formed from the wear of the road surface, traction sanding materials, tyres and brakes, as well as particles transported by wind and vehicle tyres, for example from construction sites. Concentrations of thoracic particles are particularly high in spring, when particles accumulated over the winter are resuspended into the air from drying streets by traffic and wind.