Plastic toys and child care products are being tested by a Chicago lab for the presence of chemicals that will be illegal after Dec. 1 in San Francisco.

They line the nursery section children's toy stores like brightly colored candies: rubber duckies for bathtime, chewable rings for teething, soft-covered books for pawing and mouthing. Parents shopping for their babies can be forgiven if they assume that everything on those shelves is 100% child safe. So why did the city of San Francisco issue a ban last week on the sale of certain plastic toys aimed at children under 3? And why are activists warning holiday shoppers in the most alarming terms against buying them? "Sucking on some of these teethers and toys," says Rachel Gibson of Environment California, a nonprofit, "is like sucking on a toxic lollipop."