"The dirty secret in Sofia's backyard - the coal dust that only comes at night", 10 May 2017

...In 2013, the European Environment Agency’s report on air pollution found that four of Europe’s five cities with the most consistently high levels of particulate matter (dust so small it enters deep into our lungs and stays there) were Bulgarian. Our small town of Pernik topped the list as the dirtiest one...Nothing seems to have improved since 2013...There’s...a now abandoned lignite open-pit, which used to fuel the power plant. No reclamation works have been carried out in this mine, the heap soil was left on site without any protection measures, making it very easy for the wind to carry the dust away. Until recently, this was an official mine under the concession of Recoal AD, a Belgian majority shareholder company. In 2005, the Bulgarian state signed a 10 year concession agreement with Recoal for the lignite field within the town of Pernik. In 2015, the agreement was not renewed, Recoal arguing that the costs of the facility were too high. They left without the compulsory land rehabilitation.