Note it's not a chemical agent; its bacterial spores that infect and kill mosquito larvae! I'm pretty sure they're not harmful to anything that isn't a mosquito, blackfly, gnat, or midge. Though midges are important to pond ecosystems as a source of food for fish and dragonflies and stuff? Idunno, ask this guy's wife.

I will ask her and report back...

I can imagine her having some long explanation about the unknown risks of man spreading this substance, even if its not a chemical agent. I lean on the edge of listening to Grandpa Simpson on these kind of things: https://i.imgur.com/MdjduDH.png