A string of wildfires darkened skies Wednesday and Thursday in the Pacific Northwest, where residents of the normally lush, green region experienced the world's worst air pollution.
Seattle and Portland, Oregon, were first and second, respectively, in the global ranking of places with the poorest air quality, according to IQAir, a Swiss company that measures air pollution.
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The quality was worse than in places like Beijing, New Delhi and Lahore, Pakistan, which more frequently struggle with air pollution.
On Wednesday afternoon, the Puget Sound Clean Air Agency urged residents to stay indoors.
