Ann Carlson: When L.A.'s air was both a punchline and a poison

Ann Carlson discusses her new book "Smog and Sunshine: The Surprising Story of How Los Angeles Cleaned Up Its Air." Smog was once as much a symbol of L.A. as palm trees — a bane to public health and a national punchline on Johnny Carson's "Tonight Show." An expert in environmental law, Carlson chronicles the decades-long battle that transformed the air from toxic to breathable, and what today's rollbacks threaten to undo.