So what you're asking me to believe is that this chemical, which does not occur naturally and which is biologically active, indeed quite toxic to some species,

So what you're asking me to believe is that this chemical, which does not occur naturally and which is biologically active, indeed quite toxic to some species, and which we are manufacturing and introducing into the environment in massive quantities, has no deleterious effects on animals or humans? Wouldn't that be pretty much a first? I mean, I'm not an expert here, but is there any other molecule of which all that is true? I certainly can't think of any. It's possible that humanity has just gotten very lucky in chancing on a compound that does something useful for us with no side effects (on animals or humans, that is -- as cmrdporcupine points out, there are effects on plants which weren't the intended targets -- but let's leave those aside). I can't rule out this possibility completely. But do you see why some of us think the standard of evidence should be extremely high?