There are more than 50,000 chemicals in use in industrial processes and in consumer products that we know very little about from a safety perspective—meaning safe for our health, and safe for the planet. Why? Because, as Scientific American writes, "The 1976 Toxic Substances Control Act does not require chemicals to be registered or proven safe before use."
Regular readers of this site have hopefully come across some of the No More Dirty Looks pieces, where Alexandra Spunt and I offer advice about safe alternatives to the chemical-filled consumer products we all use, every day, and we do it, and we wrote our book of the same name, because it's exactly these kinds of data gaps we find so troubling.
Scientific American has a great infographic up on their site showing that of those 50,000 chemicals, about 300 have been tested for safety, and five have been restricted. No matter how you do that math, it's deeply disconcerting.