We know that children are not simply little adults. With their quick heartbeats, fast-growing organs and enviable metabolism, the young absorb proportionally more pollutants than those who are older. Exposures to minute amounts of hormones, environmental tobacco smoke or pollutants early in the life of an animal or human embryo can deform reproductive tracts, lower birth weight and increase the chance of developing cancer. And yet results from an independent chemical testing laboratory released last week found a probable human carcinogen, 1,4-dioxane (also known as para-dioxane), in some common children's shampoos at levels higher than those recommended by the U.S. Food and Drug Administration. The Environmental Working Group, a research and advocacy organization that ran the study, estimates that more than a quarter of all personal-care products sold in the United States may contain this cancer-causing agent...