Pyro is found in oak galls, but most pyro today comes from a kind of bean pod. Gallic acid is extracted and concentrated by heat into pyrogallol. Like many natural substances, pyro is toxic if ingested. After you have use your pyro developer, it is already mostly oxidized, and in any case is safe for the drain. (Pyrogallol is also used in hair coloring, which also gets rinsed down the drain after it has done its job, but you don't see many threads about it)
Spinach, if concentrated , as raw gallol is concentrated to pyrogallol, is lethal as well. What did you do with that left over spinach?
It is right and proper learn about the chemicals you use, and to dispose of chemicals correctly. Its not good to buy in to over reactions regarding certain substances, that lead to unreasonable policies regarding use and disposal.
Chlorine bleach is truly nasty, caustic, toxic in all but the most minute quantities, and highly reactive chemical, but everyday households use it in vast quantity, and nobody worries about it.
Don't drink bleach, dont drink hair dye, and don't drink your developer. In other words, use your head, for something besides a funnel, and we will all be ok.
