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Environment status

Air quality statistics

The air quality in Oslo has shown a significant improvement the last 50 years and is better than many other cities in the world. Even though several measures have been implemented in order to improve the air quality, exceedances of the legal limits may still occur. Road traffic and wood fired ovens are the main source of air pollution in Oslo.

Air quality

Both short- and long term exposure to nitrogen dioxide and particulate matter has adverse effects on people with pre-existing respiratory illnesses. Studies have shown that there is a causal relationship between long term exposure to air pollutants and the development of respiratory illnesses.

The legal limits for air pollution are in effect in order to ensure adequate air quality on Oslo.

Particulate matter

Particulate matter are small airborne particles which are commonly separated in two size fractions; PM10 are particles smaller than 10 µm, while PM2.5 are particles smaller than 2,5 µm. The main sources of PM2.5 are derived from combustion (wood fired ovens and exhaust from vehicles), while PM10 is derived from the wear and tear of; pavement, tires and brake pads. Construction sites may also contribute to particulate emissions locally.

As of 1.1.2005 limits for particulate matter were in effect. There has been a strong focus on meeting these limits in Oslo through measures. Previous years compliance the PM10 limits were a challenge, while the last years these limits have been met.

The observed decrease in the amount of particulate matter is mostly due to the implementation of fees for studded tires, environmental speed limits and road dust prevention measures. Exceedances of the daily limit are most commonly associated with the use of studded tires and of wood fired ovens during dry and cold periods in the winter.

In 2016, laws on the limits for particulate matter were made stricter. As a consequence, unless additional measures are put in place, it is likely that heavily trafficked areas in Oslo will fail to meet these new limits.

These new stricter limits will not completely eliminate the adverse effects associated with long in terms of exposure to air pollutants. This is especially true for particulate matter.

Hence the city council have set ambitious goals that are below the limits suggested by the health authorities. However, in order to meet these goals additional measures must be put in place.


Graphic presentation PM10 – yearly limit:
The graph shows the average concentration per year of PM10 (particulate matter smaller than 10 micro meters) at different monitoring points in Oslo. The yearly limit value for PM10 is 25 µg/m3 (micrograms per cubic metre), as an average over one year. Data marked with (*) have less than 75% data coverage, or were out of service during that period, and as such cannot be directly compared with the other data points.

See graph showing yearly limits of particulate matter PM10 in Oslo sorted by monitoring site (PDF 0,1 MB)
 

Graphic presentation PM10 – daily limit:
The graph shows the number of exceedances of the 24 hour limit value of PM10 (particulate matter smaller than 10 micrometres) in Oslo. The limit value for PM10 is 50 µg/m3 (measured as an average over 24 hours), this limit should not be exceeded more than 30 days per year. Data points marked with (*) have less than 80 % data coverage, or were out of service during that period, and as such cannot be directly compared with the other data points.

See graph showing hourly limits of particulate matter PM10 in Oslo sorted by monitoring site (PDF 0,1 MB)


Graphic presentation PM2,5 – yearly limit:
The graph shows the average concentration of PM2,5 (particulate matter smaller than 2,5 µm) at the different monitoring stations in Oslo. The yearly limit value for PM2.5 is 15 µg/m3 (microgram per cubic meter), measured as a yearly average. Data points marked with (*) have less than 75 % data coverage or were out of service during that period.

See graph showing yearly limits of particulate matter PM2,5 in Oslo sorted by monitoring site (PDF 0,1 MB)

Nitrogen dioxide

Nitrogen dioxide (NO2) is a gas. The main source of Nitrogen dioxide in Oslo is derived from exhaust, especially from diesel vehicles.

Yearly limits

Measurements show that the yearly averages of NO2 has been steadily decreasing, especially after 2013. This is the case along heavily trafficked roads. In 2018, for the first time since 2010, all monitoring sites in Oslo  met the yearly limits for NO2, as described by the pollution revelations.

However, the values are very close to the legal limits. The main reason for the observed decrease in NO2 is most likely due to a  cleaner vehicle fleet in combination with, relatively, warm winters. Additionally, since 2017. there has been a slight decrease in the number of cars passing the toll ring (which in turn coincides with the implementation of time- and environmental tolls)

See statistics on nitrogen dioxide – yearly limits

Graphic presentation:
The graph shows the average concentration per year of nitrogen dioxide (NO2) at the different monitoring points in Oslo. The yearly limit value for NO2 is 40 µg/m3 (micrograms per cubic metre), as an average over one year. Data marked with (*) have less than 75% data coverage, or were out of service during that period, and as such cannot be directly compared with the other data points.

See graph showing yearly limits of nitrogen dioxide in Oslo sorted by monitoring site (PDF 0,1 MB)


Hourly limits

The number of exceedances of the limit value for hourly mean concentrations of NO2 shows a large degree of annual and local variation. The pollution regulations allow for up to 18 hours of concentrations exceeding 200 µg/m3 per year.

Exceedances of the hourly limits occur most commonly during the winter, and especially at low temperatures in combination with low winds. Under these conditions the cold air may trap the polluted air, this increasing the local concentration of NO2.

See statistics on nitrogen dioxide – hourly limits

Graphic presentation:
The graph shows the number of exceedances of the limit value of Nitrogen dioxide in Oslo. The hourly limit value is 200 µg/m3 (measured as an average over one hour), this limit should not be exceeded more than 18 hours per year. Oslo has 12 monitoring sites that measure the concentration of Nitrogen dioxide. Data points marked with (*) have less than 80 % data coverage, or were out of service during that period, and as such cannot be directly compared with the other data points.

See graph showing hourly limits of nitrogen dioxide in Oslo sorted by monitoring site (PDF 0,1 MB)

Oslo will likely continue to exceed the NO2 limits unless more preventive measures are implemented.

Tropospheric Ozone

The levels of tropospheric ozone in Oslo are low.

The main source of tropospheric (the lowest layer of the earth’s atmosphere) ozone is long-range transport from continental Europe.

The limit for ozone (the eight hour average ozone concentration) is calculated as an average over a three year period where the concentrations cannot exceed 120 µg/m3 (or 0.07 ppm) during an 8 hour period for more than 25 days a year.

The eight hour average ozone concentration limit is not exceeded in Oslo.

Graphic presentation:
The graph shows the number of days with Ozone (O3) concentrations over 120 µg/m3 (measured over an 8 hour period), and should not be exceeded more than 25 days per year. Data points marked with (*) have less than 80 % data coverage, or were out of service during that period, and as such cannot be directly compared with the other data points.

See graph showing the number of days with Ozone in Oslo sorted by monitoring site (PDF 0,1 MB)