Air pollution levels have plunged in cities across Bolivia as the country marked a nationwide car-free day in which all non-emergency vehicles were banned from city streets. As Bolivia's middle-class population has increased over the past 10 years so has the number of cars clogging city streets. The car-free event started 18 years ago in Cochabamba, one of Latin America's five most polluted cities, and has gradually taken root across the country. By 2011, it had become so popular that Bolivia's legislature declared a yearly Day of the Pedestrian and Cyclist in Defence of Mother Earth". Families love it. Jesus Romero, who lives on the northern edge of Cochabamba, said: "We really enjoy that it is so quiet and peaceful without any cars around, and that's there's space in the streets for the kids to play." Deyanira Lpez, 14, highlighted another benefit. "Our city is very beautiful but you just don't see it because of all the cars," she said. Andres Clares, 16, agreed, saying: "I really like walking at least one day without cars. It's quieter and the air is so much fresher." In a typically noisy city, the sudden silence is striking. This year the event's catchphrase is "leave your green footprint in Cochabamba". Six eco-stations are focused on different themes in coordination with local businesses and charities. "These educate about the air, animals, water, recycling, protected areas and trees," said Gaviota Borda, head of the municipal department of environmental protection.