The capitals of Bosnia, Macedonia, Kosovo and Bulgaria have been encased in heavy smog in recent days, with air pollution reaching dangerously high levels in parts of the region. The winter months bring the worst air quality, due to excessive use of coal, excessive traffic, poor spatial planning and the use of solid fuels for heating homes.

See more at: http://www.balkaninsight.com/en/gallery/balkan-cities-enveloped-in-smog-as-air-pollution-soars-12-05-2018