September 7 is the International Day of Clean Air for Blue Skies, designated by the UN General Assembly in 2019. According to the UN, the designation should reflect the global community’s growing awareness of the risks of air pollution and should emphasize the need for a greater effort to improve air quality, to safeguard the health of people and the environment.

“In large parts of the world, air pollution is still a major problem that leads to poor health, diseases and death,” says Joana Soares. She is a senior scientist at the climate and environmental research institute NILU.

Air pollution is caused by gases and particles released into the atmosphere from a variety of human activities, such as inefficient burning of fuels or open burning of waste, agriculture, and farming. There are also natural sources that contribute to air pollution, many of which are influenced by human activities such as forest fires, soil dust and salt in sea spray.

Soares explains that particulate matter (PM10 and PM2.5) and nitrogen dioxide (NO2) are the air polluting components that contribute most to air pollution in Norway (see fact boxes). In addition, ozone (O3) is an important contributor to air pollution in warmer places.

All Nordic capitals do well, but Oslo is worst among them

The European Environment Agency (EEA) regularly publishes a ranking of several European cities that provides information on air quality, categorizes the air quality, and ranks the cities from the least to the most polluted, based on average levels of fine particulate matter (PM2.5) the last two years.

The reports are prepared by the European Topic Center on Human Health and the Environment (ETC HE). The Norwegian climate and environmental research institute NILU, which has collaborated with the EEA for 30 years, heads and coordinates the international collaboration at ETC HE.

A new research report from ETC HE proposes a new way of ranking European cities that also includes other air pollutant components such as nitrogen dioxide (NO2) and ozone (O3).

“The ranking has been somewhat controversial. Still, the new methodology will give us a more complex picture of the situation, where cities that are particularly exposed to particulate matter do not fare worse than cities that have more of the other components,” says Joana Soares. She is one of the authors of the report together with other researchers from NILU, EEA, and the Czech Hydrometeorological Institute (CHMI).

According to the ranking in the report, Oslo is the Nordic capital with the most air pollution. In total, Oslo ends up in 66th place out of 760 cities, well behind Copenhagen in 47th, Helsinki in 20th, Stockholm in 10th and Reykjavik in 6th place.

“Much of the reason why Oslo ends up so far behind the others has to do with geography. Stockholm and Copenhagen, for example, are open cities, with more wind. Even with the same number of sources of pollution, the lack of wind in the Oslo basin will mean that you get accumulation of pollutants in the atmosphere due to longer stagnation periods,” says Soares.

Cold winters with a lot of wood burning and the sprinkling of gravel and salt on the roads also contribute to elevated levels of particulate matter in Oslo. The Norwegian capital is still in the top 10 percent of cities in Europe.

Among the Norwegian cities included in the ranking, Tromsø is the least polluted in 15th place. Bergen is in 18th place, Trondheim in 21st and Stavanger and Kristiansand in 28th and 29th place respectively.

Important international cooperation

EEA, through ETC HE and its predecessors, has for ten years produced research to assess air pollution and its health damage (environmental burden of disease, EBD).

“This international cooperation is particularly important to follow up the European Commission’s goal of reducing so-called attributable deaths from air pollution by more than 55 percent from 2005 to 2030,” says Soares.

She explains that cooperation across national borders, together with international legislation, helps drive emissions down.

European Topic Centers (ETC) are consortia of institutions from the various countries that are members of the EEA. Each theme center is assigned to solve various challenges and tasks within a given environmental area in the EEA’s strategy and management plan.

The ETCs form interdisciplinary networks where experts from European countries meet and collaborate to find sustainable solutions for their thematic area. This collaboration in turn contributes to building up local expertise on environmental and climate change and sustainable sector policy in the countries.

“We come together from similar institutes, with different strengths. Through the ETC collaboration, we can complement and help each other and get the research out to the European countries through the EEA,” says Soares.

Back to pre-covid levels

During the Covid 19 pandemic, when restrictions meant that more people drove less and worked from home, the researchers could see a clear decrease in air pollution. This particularly applied to NO2, which is mainly caused by emissions from road transport.

“For NO2, there was a very visible reduction. For particulate matter, it was not as clear because it is also linked to industry and agriculture, which continued during the pandemic,” explains Soares.

Unfortunately, the levels quickly shot up again after the restrictions disappeared. Now, the levels are roughly where they were before the pandemic. The exception is NO2, which after a steep upward curve has gone down a bit again.

“There were probably many people who, right after the pandemic, were still skeptical about using public transport again. They may have chosen to drive their own cars for a while, but now they are back to their old travel patterns,” Soares speculates.