WASHINGTON — Senator Amy Klobuchar, D-Minn., introduced legislation to strictly limit levels of harmful toxins in baby food. The Baby Food Safety Act, co-sponsored by Tammy Duckworth in the Senate and Raja Krishnamoorthi and Tony Cárdenas in the House, is a response to a government study that found products from leading national brands contain dangerous levels of heavy metals. “Even small amounts of metals can have an effect on little babies,” Klobuchar said. The bill would give new mechanisms to the U.S. Food and Drug Administration to enforce regulations.