WFS API

From the dataset abstract

The dataset shows the areas where the annual limit value for nitrogen dioxide (40 µg/m3) has exceeded or has been in danger of exceeding.

In 2022 it was estimated that the annual limit value of nitrogen dioxide will no longer exceed nor it is in danger of exceeding in Helsinki metropolitan area. For that reason a new yearly data will not be published.

The exceeding area was assessed and updated annually, at the end of the year in question. The assessment was carried out not only on the basis of the monitoring results for that year, but also taking into account the monitoring results and weather conditions of previous years.

The data is in a geographic dataset format (.shp and WMS interface). It can be downloaded from the map service at kartta.hsy.fi (under “Latauskori”) and from these pages as a Shapefile.

Via the WMS interface, data is available from 2004 onwards.

Nitrogen dioxide concentrations and exceeding the limit value are affected by traffic emissions and the ventilation of the area. Concentrations of air pollutants are higher on streets lined with tall and continuous buildings. The dilution of air pollutants is weaker in such areas.

Read more about the impact of traffic on air quality and measures to improve air quality.

WMS API: https://kartta.hsy.fi/geoserver/wfs, layer: No2_ylitysalueet_VVVV

Attribute data:

• katu: street name
• raja_arvo: limit value: indicates whether the annual NO2 limit value is exceeded or in danger of being exceeded in the area in question
• arviovuosi: year of assessment of the exceeding area

Preview and download data in HSY's map service.

Source: Pääkaupunkiseudun typpidioksidin vuosiraja-arvon ylitysalue