photographers are calling it 'haze'

 @kovaldesign: it comes from aircraft exhausts

 @baggyferret: funny enough, but the town behind the hills is told to be one of the most polluted in Poland, despite being surrounded by mountains and hectares of forest. I suppose its geological location may contribute to that, where mountain acts as a barrier, holding the fumes. And lets not forget, south of the country is heavy industry, similar to Ruhr Area in Germany (see this old Poland map for reference www.lib.utexas.edu/maps/europe/poland_ind_1977.jpg)

 @kovaldesign: for a complete picture you need to know the polutant, i'd bet it's nano aluminium and barrium, strontium particles...check the water too and local peoples blood your answer will be clear, unlike the air! it is very blue don't you think?

 @baggyferret: It may be the case, but you don't expect me to go and check But it may simply be too much saturation after I put the photos through editing program.

 @kovaldesign: it is the case, need proof? find me a long range clear photo after 2010.....