Click here to see Tümer's photos. Photo: Laurie Tümer. In a segment this fall, Good Morning America simulated pesticide exposure in a New York City classroom. Using a powder visible only under black light, the program showed how far chemicals could spread through an activity as simple as child's play. The eye-opening exercise wasn't news to Laurie Tümer. The photographer has been making images that expose the presence of synthetic pesticides since 1998, when she suffered near-fatal poisoning after her New Mexico home was sprayed. While recovering, Tümer discovered a muse in the work of Richard Fenske, an environmental scientist …