STEVE INSKEEP, HOST:
Good morning. I'm Steve Inskeep. The mountains that loom over Tehran look different almost every day. Partly, it's the weather. Partly, it's the smog. You can choke on the air in that giant city. But on Monday, commuters were gasping with surprise. Hassan Rouhani rode the subway. The president of the oil-rich state took mass transit to work. He brought along the foreign minister, taking a moment off from nuclear negotiations. They were together marking Iran's national clean air day. It's MORNING EDITION. Transcript provided by NPR, Copyright NPR.