PARIS, FRANCE - DECEMBER 16: The Eiffel Tower and the city of Paris surrounded by high levels of air pollution seen from the Generali balloon on December 16, 2016 in Paris, France. The alternating traffic circulation is again being established on Friday in Paris and its suburbs because of pollution. The police and authorities have decided to deploy this system once again, with only vehicles with certain number plates being able to circulate and a reduction of speed of 20 km/h over the entire road network. (Photo by Chesnot/Getty Images)
