Air quality in Oslo varies both seasonally and geographically. All parts of the city have good air quality in summer, but air quality in winter varies throughout the city. The city of Oslo is located in a large pot formation in the enclosing surroundings. The lower-lying parts of the city are most exposed to air pollution. On the hillsides, on the other hand, air quality is generally good also in winter.
This topography of Oslo contributes often to inversion in the winter. Inversion causes high levels of local pollution in the centre of the city and along the main roads.
Here you can see a typical pollution distribution in the centre of Oslo.
In these areas, there is moderate to poor air on 30-45% of all days in winter, but on only up to 3 percent of all days in winter have very poor air quality.
There is no industry in Oslo. Thus the main contribution of the air pollution comes from the traffic (50%-70%). In the winter wood heating of old houses also contributes (up to 50% in the centre).
Table for the forecasting classes (national standard)
||No health effect
||100 - 150
||35 - 50
||35 - 60
||Asthmatics may experience health effects in these areas,
especially during physical activities.
||150 - 200
||50 - 100
||20 - 35
||Asthmatics and people with serious heart
and bronchial diseases should avoid longer outdoor stays in areas with high air pollution.
||Asthmatics and people with serious heart and bronchial diseases should avoid areas
with very high air pollution. Healthy people may experience incidentally irritations
in the mucous membrane and unpleasantness.