Millions of Americans may be putting a cancer-causing ingredient in their mouths every day. Triclosan, an ingredient in Colgate Total toothpaste, has been linked to cancer-cell growth and disrupted development in animals, leading many consumer companies to phase it out and Minnesota to ban it in many products. But Colgate Total uses it to stave off gum disease and cites the Food and Drug Administration’s approval of the toothpaste 17 years ago as evidence that it is safe. Pages describing the FDA’s process only became available this year and show that the agency uses company-backed science (!) to declare products safe. In the meantime, newer studies have detected triclosan in the urine of 75 percent of 2,517 Americans tested. A 2012 study linked triclosan to reduced fertility in mice and a 2013 study linked it to lowered sperm production in rats.