Despite expectations to the contrary, the energy crisis has so far not significantly affected air quality in Slovenia. Although raised values of the harmful polluting particles PM10 were recorded in recent days, the Environment Agency (ARSO) says this is typical for sunny winter days without wind.

"The data are not yet definitive, but preliminary figures show the air was less polluted with particles last year than in 2021, mainly due to weather conditions, which have substantial impact on how pollutants in the air are diluted," Tanja Koleša, ARSO's air quality expert, told the STA.

There was for instance more rain in the months when the concentration of particles in the air is higher. December last year was wetter than December 2021, which means that particulate matter was being washed out of the atmosphere. Apart from rain, wind influences particle concentrations as well.

Thus the same energy sources and the same amount of emissions from small heating systems, transport and industry can result in lower concentrations of particulate matter if the weather is favourable. The opposite happens if there is a temperature inversion - the atmosphere is stable, emissions are held close to the ground and cannot be diluted into the atmosphere.

This January was very wet as well and the air pollution levels were extremely low compared to the same month in previous years despite people using individual heating in the face of the energy crisis. In Ljubljana the limit values were exceeded ten times in January 2022 and only twice in January 2023.

The capital is as a rule among Slovenian cities affected the most by air pollution. The leader is Murska Sobota, where values at one measuring spot are exceeding the other "leading" pollution spots in the country by a factor of four. ARSO is still trying to determine the reason for this.

Last year the limit value for PM10 was exceeded in Murska Sobota 39 times, while the allowed number of such days in a year is 35. Two measuring spots in Celje had 13 such days, one in Koper recorded 12 and three in Ljubljana recorded 11.

According to the agency, particle concentrations are high mainly in the morning and evening, and they decrease somewhat during the day. Hourly particulate matter values and the air quality index can be monitored on ARSO's website.