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. 2016 Mar 1;124(3):A56. doi: 10.1289/ehp.124-A56

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graphic file with name ehp.124-A56.g001.jpg — Remotely sensed data indicate that levels of NO₂ decreased in North America and other high-income regions between 1996 (left) and 2012 (right), likely as a result of assorted policy and economic factors. Other areas fared worse, with levels in industrialized China more than doubling.

Source: Geddes (2016)²