Heavy layer of fog, covering entire city of Sarajevo is seen, from a high point on Mt. Trebevic, on December 4, 2018. - Bosnia and Herzegovina's capital has been covered in smog for past several days. Measurements taken by local air pollution measurement stations have shown variations between 190 and 300 microgrammes of hard matter particles per cubic meter of air, which puts Sarajevo among 5 most polluted cities in the world. (Photo by ELVIS BARUKCIC / AFP)