> I'm not sure anyone really knows just how little imidacloprid will > have negative effects on bees. That is precisely the point. Now that we can detect what were unimaginably small amounts of substances only a decade ago, we are starting to realise that even a few stray molecules of some things can have very significant efffects. > From what our counterparts in France > say, even plants grown from seeds that were treated with imidacloprid > killed bees. I don't know how to do the math for this, but it has to > be smaller than 20 ppb, I'd bet money that a French beekeeper would > take issue with 6 ppb. Actually, it *was* a French beekeeper who was suggesting 6 ppb a few years back, in the face of strong resistance, but I suspect that even that tiny amount may prove to be huge when the compound is fully understood. The question of concentration in flesh of toxins due to passage up a food chain or concentration in water due to evaporation is meaningful, but perhaps an understanding that places emphasis on concentration, rather than the basic nature of the substance in question may detract us from possible trigger-type, key-like or catalytic action mechanisms that may be less dependant on concentration that on the shape and other characteristics of the molecule. Conceivably there could be substances for which zero tolerance must actually mean zero -- ie. not one molecule! I'm not seriously suggesting that the substances currently under discussion here are, in fact, such compounds, but then again... what do we really know? allen