The concentration of fine particles in Sarajevo in the afternoon was 47 times higher than the World Health Organization's threshold.

The city's air quality index hit 320, according to IQ Air data, which measures global air pollution -- anything above 300 is deemed dangerous.

Pollution peaks are frequent in Sarajevo, a city of more than 400,000 people, surrounded by mountains and where temperatures plunge in winter.

"The biggest issue is individual heating," said Anes Podic, head of the environmental organisation Eko-Akcija, adding that between 30,000 and 40,000 households use solid fuels, mostly wood.

"They burn damp wood in very poor quality stoves, and we end up with very high emissions."

But the government "doesn't want to solve the problem", he said, and "as a consequence, we are often topping (pollution) black lists, alongside much larger cities of 10, 20 or 30 million inhabitants".

The effects of pollution on local residents are well documented, including in the region.

According to a UN study published in 2019, air pollution was responsible for 20 percent of all premature deaths registered in 19 Balkan cities.

Balkan residents lose up to 1.3 years of life as a result of air pollution, the UN study indicated.

"I feel the symptoms but I am so used to it, it's almost a daily thing," local resident Ognjen Grujic, 46, told AFP.

Air pollution, worsened by climate change, increases the risk of suffering form respiratory diseases, cardiovascular diseases, diabetes and cancer.

"In Sarajevo, one out of 12 deaths is a result of lung cancer," Podic said.

According to certain experts, it has similar, possibly even greater effects than smoking or alcohol consumption.

In Sarajevo, mountains are the only escape.

"It's very hard to breathe and to live in Sarajevo during these smog episodes," said 66-year-old retiree Senada Dzaka.

"Sometimes it stays like that for several days in a row and it makes people depressed. It would be really difficult to live if we didn't have the option go to the mountain," she said from the top of Mount Trebevic, gazing at the city wrapped in a thick cloud of smog.