In some of the dirtiest places on Earth, author and environmentalist Andrew Blackwell found some beauty. His book, Visit Sunny Chernobyl, tours the deforestation of the Amazon, the oil sand mines in Canada and the world's most polluted city, located in China. — npr.org

“Both L.A. and Mexico City have improved but in Mexico City, the change has been a lot more,” said Luisa Molina, a research scientist with the Massachusetts Institute of Technology, who has done extensive pollution comparisons. Mexico “is very advanced not just in terms of Latin America, but around the world. When I go to China, they all want to hear the story of Mexico.” — nytimes.com