Soaring concentrations of hazardous fine particles in Central Europe have been traced back to parched farmland left to gather dust to the east in the Ukraine. In spring 2007 levels of particulate matter (known as PM10) reached almost 30 times the European average in parts of Slovakia, Poland, the Czech Republic and Germany. Air quality specialists looking into the event now believe the dust originated from fallow land on Ukrainian farms and was carried west by unfavourable winds.