Two years ago researchers outfitted an electric Toyota RAV4 with a set of test instruments and drove back and forth near four Los Angeles County freeways between 4:30 a.m. and 6:30 a.m., sampling the air. 
The results confirmed that in the early morning, concentrated plumes of air pollution from freeways can travel more than a mile downwind, exposing more residents than previously thought to harmful pollution levels.
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