Kim Boekelheide with TreeHugger hero Meg Kissinger
Toxins are from biological sources only. They are "a poisonous substance produced by living cells or organisms." Snake venom is a toxin; Bisphenol A or artificial chemicals are Toxicants. Pedant that I am, my post Today's Toxin: Atrazine, the Weed Killer in your Water is embarrassing.
When used non-technically, the term "toxin" is often applied to any toxic substances. Toxic substances not of biological origin are more properly termed poisons. Many non-technical and lifestyle journalists also follow this usage to refer to toxic substances in general, though some specialist journalists at publishers such as the BBC and The Guardian maintain the distinction that toxins are only those produced by living organisms.
But if a prominent toxicologist thought it important enough to make it his first slide, maybe those " non-technical and lifestyle journalists" should attempt to get it right.