Major world cities are facing serious pollution issues, because with more people almost always comes more pollution. The "Paris Breathes" campaign is looking to reverse some of the air pollution caused by its high volume of cars by instituting one car-free day a month in many neighborhoods. The campaign launched in May 2016 after a very successful test run on September 27, 2015. On that day, there was a 40% drop in nitrogen dioxide levels in some parts of Paris. As part of the campaign, more than a dozen sections of the city go car-free the first Sunday of every month. Certain zones will be car-free for specific periods of time, ranging from four to 10 hours on those days. A few of the neighborhoods will only go car-free once a month for the summer months. Paris mayor Anne Hidalgo hopes the campaign will significantly decrease the air pollution and smog in the city. These first Sundays also coincide with free admission days to the city's national museums. We've collected some awesome videos on this topic. Watch them now to learn more.