On Thursday, a dense fog blanketed Sarajevo, leading to flight cancellations, children being advised to stay indoors, and a halt to outdoor construction activities.

Winter in Sarajevo frequently brings intense pollution, primarily due to heating needs and vehicle emissions. The city’s location in a mountain-enclosed valley often traps pollution, leading to prolonged periods of poor air quality without wind to disperse it.

Several flights were grounded at Sarajevo airport, and commuters faced slow-moving traffic due to limited visibility during the morning rush. Many residents donned face masks to shield themselves from the hazardous air.

According to the Swiss air quality firm IQAir, Sarajevo’s air was deemed “unhealthy” on Thursday. The city regularly ranks among the worst globally for air pollution.

Authorities took measures on Wednesday, banning heavy trucks over 3.5 tonnes from the city center and prohibiting vehicles that fail to meet EU environmental standards. Additionally, outdoor construction and public gatherings have been suspended.

Experts have warned that exposure to PM2.5 – fine inhalable particles with a diameter of 2.5 micrometres or smaller – has led to a rise in respiratory infections as well as cancer, cardiovascular diseases and premature deaths in Sarajevo, other major cities in Bosnia and elsewhere in the Western Balkans.

Many Balkan countries have a poor record in environment protection despite promises to improve the situation as they seek to move closer to EU membership. Balkan rivers are often clogged with garbage and recycling is almost non-existent, while many cities have seen rampant construction diminishing green areas.

The air in Belgrade, the capital of neighbouring Serbia, also was deemed “unhealthy for sensitive groups” on Thursday.