F.D.A. Approves a Challenged Food Dye
FDA plans to approve permanent use of artificial food coloring Red No 2 although some of agency's own scientists say there are questions about whether it may cause cancer, birth defects or fetal death; agency says it has completed new fetal toxicity tests which it says show no harmful reproductive effects; consumer groups, including Ralph Nader's Health Research Group, and Center for Science in Public Interest, have protested FDA's decision; illus of researcher Dr Jacqueline Verrett who says evidence against Red No 2 is strong (M)