In the three cities, the Air Quality Index (AQI), which measures a range of pollutants, exceeded 150, which is considered unhealthy.
In Paris and Los Angeles, it was 44 and 34, respectively.
The extreme pollution in the three Balkan capitals coincided with the drop in temperatures.
In the Serbian capital Belgrade, the concentration of particles 2.5 microns in diameter or less (PM2.5) reached 98 micrograms per cubic metre. It is more than 19 times higher than the World Health Organization's annual recommendation.
PM2.5 particles pose a serious health risk if inhaled for prolonged periods of time as they are small enough to enter the bloodstream.
In Sarajevo, the capital of neighbouring Bosnia, the situation has worsened over the past few days, especially in the evenings, due to the tens of thousands of homes using coal and wood for fuel.
In some parts of the city, the concentration of PM2.5 particles exceeded 300 micrograms per cubic metre.
Experts say Balkan cities suffer from chronic air pollution for several reasons, pointing mainly to the burning of fossil fuels - coal in particular - in various forms and outdated technology.
They say the start of the heating season exacerbates the problem.
"With the burning of low-quality coal and wood, and which is particularly characteristic of our region, the burning of all kinds of waste - old furniture, clothes, plastic - and in the worst case the use of engine oil for heating, we get the picture. Combined with heavy traffic in big cities, this means extreme pollution," says Dejan Lekic from the National Environmental Association in Belgrade.
According to a 2019 UN study, air pollution is responsible for 20% of premature deaths in 19 Balkan cities.
People living in the region lose up to 1.3 years of their lives on average due to air pollution, the study shows. | BGNES
