PARIS, FRANCE - MARCH 23: A general view of the Parc des Princes and the peripheral road surrounded by high levels of air pollution on March 23, 2015 in Paris, France. Paris authorities have introduced emergency measures to help control pollution levels, such as alternate driving days in Paris, limiting cars to 20 kilometres per hour and vehicles with number plates ending in an even number will be banned from the roads of Paris and surrounding suburbs. (Photo by Xavier Laine/Getty Images)
