WHO PM2.5 guideline exceeded in 15 of 33 Finnish municipalities in 2025
The WHO 2021 PM2.5 annual guideline of 5 µg/m³ was exceeded in 2025 in 15 of the 33 Finnish municipalities that published an annual mean. The cleanest of those was Rovaniemi at 2.4 µg/m³, and the highest figure was Mariehamn's 6.6 µg/m³.
This is 33 municipalities, not the whole country. Finland has 308.
The 2025 ranking
A municipality's figure is the 2025 median of its stations, to 1 decimal. Ranking and WHO comparison use 2025 only. Municipality names follow the dataset, which is why Mariehamn and Jakobstad appear in Swedish.
| Municipality | 2025, µg/m³ | Stations |
|---|---|---|
| Rovaniemi | 2.4 | 1 |
| Sotkamo | 3.3 | 1 |
| Siilinjärvi | 3.7 | 4 |
| Tornio | 3.7 | 2 |
| Kokkola | 3.9 | 2 |
| Tampere | 3.9 | 3 |
| Raahe | 4.1 | 1 |
| Oulu | 4.2 | 1 |
| Raisio | 4.4 | 1 |
| Hollola | 4.5 | 1 |
| Kouvola | 4.5 | 1 |
| Kuopio | 4.5 | 5 |
| Jakobstad | 4.5 | 1 |
| Harjavalta | 4.6 | 2 |
| Joensuu | 4.6 | 1 |
| Jyväskylä | 4.7 | 2 |
| Rauma | 4.7 | 1 |
| Varkaus | 5.0 | 1 |
| Lahti | 5.1 | 3 |
| Savonlinna | 5.1 | 1 |
| Hämeenlinna | 5.2 | 1 |
| Lappeenranta | 5.3 | 5 |
| Lohja | 5.3 | 1 |
| Kotka | 5.4 | 2 |
| Pori | 5.4 | 1 |
| Espoo | 5.6 | 3 |
| Kemi | 5.6 | 1 |
| Imatra | 5.8 | 1 |
| Helsinki | 5.9 | 6 |
| Turku | 5.9 | 1 |
| Porvoo | 6.0 | 1 |
| Vantaa | 6.1 | 2 |
| Mariehamn | 6.6 | 1 |
Varkaus at 5.0 µg/m³ does not exceed the guideline: an exceedance is a rounded value greater than 5.0. The 15 that exceeded were Lahti 5.1, Savonlinna 5.1, Hämeenlinna 5.2, Lappeenranta 5.3, Lohja 5.3, Kotka 5.4, Pori 5.4, Espoo 5.6, Kemi 5.6, Imatra 5.8, Helsinki 5.9, Turku 5.9, Porvoo 6.0, Vantaa 6.1 and Mariehamn 6.6.
The same 15 exceed on the unrounded medians, so the count does not turn on the rounding.
None of the 33 exceeded the EU 2030 target of 10 µg/m³ or the EU limit of 25 µg/m³. Even the highest figure, 6.6 µg/m³, is well below both.
The single-station municipalities
In 20 of the 33, the figure comes from one station. Both ends of the ranking are among them, and in both cases it is worth knowing which station.
Rovaniemi's 2.4 µg/m³ comes from one monitor, Ranua Suhanko Palovaara. It sits 42 km from the centre of Rovaniemi and 31 km from the centre of Ranua — closer to the neighbouring municipality, which is also what it is named after. The station in central Rovaniemi, Rovakatu, has a complete 2025 measurement period but no PM2.5 reading. So Rovaniemi's figure is a reading from a forest site, not from the city itself.
Mariehamn's 6.6 µg/m³ likewise comes from a single station, Ålandsvägen.
For contrast, Helsinki's 5.9 µg/m³ is the median of six stations. Its highest, Kustaa Vaasan tie at 6.8 µg/m³, does not set the municipality figure — the figure is a median, not the highest station. Mäkelänkatu has a complete 2025 measurement period but no PM2.5 reading.
How the figures are calculated
The variable is aq_pm25_avg, the Finnish Meteorological Institute's PM2.5 annual mean. A
municipality's value is the median of its stations for that year, to 1 decimal. With one station,
that station is the municipality value.
A station counts only when its measurement period is marked complete and an annual mean can be computed. The 2025 set is 33 municipalities and 61 stations. Five rows marked complete carry no value, because fewer than 75% of the year's hours are valid. There is no minimum station count and no population floor.
The WHO annual guideline is 5.0 µg/m³, the EU 2030 target 10 µg/m³ and the EU limit 25 µg/m³.
What the figures do not say
Finland has 308 municipalities. 61 have an air quality station, and 36 have published a PM2.5 annual mean in some year. In 2025, 33 did. A municipality that does not measure is neither clean nor dirty here — it is simply not on the list.
The set also grows year by year: in 2021 it was 21 municipalities and 33 stations, in 2025 it was 33 and 61. So rankings from different years cannot be compared, and this article cannot tell you whether air quality in Finland has improved or worsened.
Check it yourself
The figures for all 33 municipalities are downloadable as CSV above: pm25-kunnittain-2025.csv. Rows are ordered by the 2025 median, cleanest first, with each municipality's station count. The chart is drawn from this same file, so the article and the figure cannot disagree.
The API gives the same ordering:
https://suomiatlas.com/api/v1/air-quality/kunta-ranking?pollutant=aq_pm25_avg&year=2025.
It returns the same 33 municipalities in the same order.
Source: Finnish Meteorological Institute (FMI), open data (CC BY 4.0). All 33 figures were checked against Suomiatlas's published API on 31 August 2026.
Analysis: Suomiatlas. Questions and corrections: [email protected]