Huffington Post: A couple of years ago, my extended family gathered for Thanksgiving in Los Angeles. Looking across a splendid vista over the city, my 40-something nephew asked me, "Is it true that 40 years ago you couldn't see the hills on the other side?" Progress, I thought, that he really had no idea how smoggy it used to be. And that's a source of satisfaction for one who spent his career working to clean the air.
But progress brings a new burden: to tell the history of how the air got cleaned up. And to...