Because of high industrialization and the lack of wind due to being closed between mountain ranges air pollution remains a severe problem in Northern Italy. Even if smog levels have decreased dramatically since the 1970s and 1980s, in 2005 a team of researchers at the Royal Netherlands Meteorological Institute reported that Northern Italy was one of Europe's most polluted areas in terms of smog and air pollution due to its climatic and geographic conditions, which cause the stagnation of pollutants.[10]