We are diving into the Toxic 10 ingredients commonly found in mainstream toothpaste (that no one asked for!) Next up: Propylene Gylcol. A synthetic chemical compound used as a surfactant, it’s also used in antifreeze, paints and enamels. It’s found in toothpaste to smooth out the texture. Highly toxic to humans, this compound is known to irritate the skin, eyes, lungs and mucous membranes. Fun..