No dogs, food or beverages are allowed on the artificial turf field at the  Silver Terrace Playground at Silver Avenue and Ledyard Street, Thursday January 3, 2008, in San Francisco, Ca. A group of neighbors in Potrero Hill are fighting a plan to install artificial turf at the playfield at their local recreation center, raising concerns that the synthetic material could have negative health and environmental effects.(Lacy Atkins  San Francisco Chronicle) Photo: Lacy Atkins, SFC