L.A. gets a bad rap for its car culture. But it turns out that Americans' addiction to milk, cheese, and other delicious dairy products plays just as big a role in the city's smog problem these days. Scientific American reports that there are 300,000 cattle in the L.A. area, and the bacteria feasting on their waste create the same tiny particles of pollution that make smog particularly nasty.
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Sarah Laskow is a reporter based in New York City who covers environment, energy, and sustainability issues, among other things. Follow her on Twitter.