People ride a cable car up Mt. Trebević as Sarajevo is obscured by a layer of fog and pollution. Temperature inversion, which occurs when air at high altitudes becomes warmer than the air below, often keeps smog trapped in the city below.

Smoke billows from the chimney of a bakery during a heavily polluted day in Sarajevo. Widespread burning of wood, poor quality coal, tires, plastic and rubbish contribute to periods of poor air quality during the winter.

A woman takes photos in Sarajevo’s iconic “Pigeon Square” on a day when the city was one of the most polluted in the world, with an Air Quality Index (AQI) rating of 350. During the winter, Sarajevo often reaches the position of world’s most polluted city, outranking usual placeholders like New Delhi, Kolkata, Beijing and Dhaka.

Smog hangs over Sarajevo on a heavily polluted winter day. The city’s geography, located in a basin surrounded on all sides by mountains that make up part of the Dinaric Alps, contributes to often lengthy periods of poor air quality during winter months.

A street along the Miljacka river during a heavily polluted day in Sarajevo. Older cars with high C02 output from the 70s or 80s are still common on Bosnia’s roads, one of several contributing factors to days of poor air quality in the city. On especially polluted days, local emergency regulations limit the use of some cars that don’t meet more modern emissions standards.

A paraglider takes off from Mt. Trebević as smog hangs over East Sarajevo.

Pollution hangs in the air near Sarajevo’s Academy of Fine Arts.

People take photos at a holiday lights display with heavy pollution hanging in the air at the Skenderija center in Sarajevo.

Smoke rises from the chimney of a house in the Hrid neighbourhood of Sarajevo. The city has a high concentration of individual households, many older and still relying on traditional stoves or fireplaces for heating. Many poor households burn low quality fuels such as coal or plastics, contributing to higher levels of pollution.

People wait at a bus stop on a day when Sarajevo ranked among the most polluted cities in the world with an AQI rating over 300.

A view of Sarajevo covered in a layer in smog seen from Čavljak, a popular outdoor area 10km outside the city.

A neighbourhood in the hills above Sarajevo on a heavily polluted day. Individual households stretch into the hills on either side of the city, where many lower income families live and rely on poor quality fuels burned in stoves or fireplaces for heating.

Signs of logging on Mt. Trebević above Sarajevo. Use of wood for heating contributes to deforestation and illegal logging throughout Bosnia.

A shed stocked with wood next to an old Yugo on the outskirts of Sarajevo. Use of wood for heating along with high numbers of old cars on Sarajevo’s roads both contribute to poor air quality throughout the year.

Smoke rises from a chimney on a heavily polluted day in Sarajevo.

Smog hangs in the distance of Sarajevo in this view down Maršala Tita street in the city centre.

A tram waits to depart at a stop across from Sarajevo’s City Hall on a heavily polluted night.

Smog hangs in the air over a neighbourhood above the Miljacka river in Sarajevo.

People walk down Maršala Tita street on a heavily polluted evening in central Sarajevo.

Smoke rises from a block of apartments in central Sarajevo. Many of the city’s large apartment blocks use oil fired boilers for their central heating systems, contributing to especially poor air quality in neighbourhoods with a high concentration of apartments.

People cross Sarajevo’s iconic Latin Bridge on a heavily polluted morning.

Smog envelopes Saint Joseph’s Catholic church in central Sarajevo.

A man walks his dog along the banks of the Miljacka river on a heavily polluted evening in Sarajevo.

Cable cars rise out of a layer of fog and pollution on Mt. Trebevic, above Sarajevo. During periods of heavy pollution, the price of a return ticket is halved to encourage residents to spend time in the fresh mountain air.

People picnic and take in the views near a mountain hut on Mt. Trebević as a layer of smog blankets Sarajevo below. The mountain often becomes incredibly crowded on weekends, with visitors spending time in the sun and fresh air of the mountain.