A truck engine is tested for pollution exiting its exhaust pipe as California Air Resources field representatives (unseen) work a checkpoint set up to inspect heavy-duty trucks traveling near the ... more 
A truck engine is tested for pollution exiting its exhaust pipe as California Air Resources field representatives (unseen) work a checkpoint set up to inspect heavy-duty trucks traveling near the Mexican-U.S. border in Otay Mesa, California September 10, 2013. REUTERS/Mike Blake less 
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Reuters | Photo By � Mike Blake / Reuters / Reuters
Mon, Sep 23, 2013 8:55 AM EDT