“Norco, twenty-five miles upriver from New Orleans, is the site of a massive Shell Oil refinery. Throughout the day, natural-looking clouds, nicknamed ‘Norco cumulus,’ hover over the site, created by the comingling of moisture and volatile hydrocarbons that originate in the process of refining gasoline, jet fuel, cooking oil, and other products. In 2009 the EPA ranked Louisiana as one of the top ten polluters of air and water in the United States.” —Richard Misrach