The same guy tipped me to a thing I'd not have guessed exists.
A food additive adored by health food enthusiasts and reputed to treat a number of ills when ingested orally....
https://www.amazon.com/Diatomaceous-Earth-Food-Grade-10/dp/B00025H2PY/ref=sr_1_5is also a pesticide suitable for home insect control and (if you are careful to get the food grade stuff) safe for direct application to your pets as a flea powder.
https://www.amazon.com/Bonide-Products-121-037321001218-Diatomaceous/dp/B00PWX6H8O/ref=sr_1_21Yes, those are literally the same product. 99+% pure diatomaceous earth with no additives, fillers or diluents. Uh, since that's actually silicon dioxide, I really have no idea what the 'Organic' claim in the first product description means. That's not 'organic' in ANY interpretation of the word I understand.
Apparently this is also sold in a "pool grade" or "filter grade" purity for some other applications, and those should NOT be used for either of the above two applications because it contains impurities (which can be poisons) or bits that might not be finely enough powdered - which could possibly act like tiny bits of fiberglass if inhaled. Food grade product is free of both.
I had known about diatomaceous earth for pest control for some time, but hadn't appreciated how COMPLETELY harmless the food grade variety really is to us mammals.
This is just silicon dioxide - which is to say, a type of powdered rock one hundred percent inert with respect to our digestive enzymes and body chemistry. I have no idea what benefits the foodies think they're getting out of this, they might as well be swallowing a marble. This stuff is safer than garden dirt.
Except to chitinous insects. The powdered bits are sharp and just a bit harder than an insect's shell. Once a bug gets some of this powder on its shell, whenever it moves the stuff abrades the shell - until it wears thin enough for water to evaporate through and the bug dehydrates. Kills 'em dead in an average of 3 hours. It's not a 'poison' as we understand the term, because its action is purely mechanical.
But we mammals can eat it by the spoonful if we want. It's hydrophilic, and with water sticking to it the sharp abrasive bits aren't exposed. Because our digestive system isn't bone-dry, it gets wet and that makes it inert. It can't do anything to us. Well, except make us excrete water so we have to drink a bit more.