First I'm hoping this is in the right section. There is a big debate in the high plains of the Rockies and the Pacific Northwest about coal being transported by rail in open top hopper cars. The debate seems to center on coal dust and bits of coal making its way into the water ways. As far as I can find the reason that the environmental groups says that this is a bad thing is that the coal will then cause elevated levels of heavy metals in the water ways, and these metals will enter into the food chain. My question I was hoping that could be cleared up is what is the process that causes a bound heavy metal in a stable matrix to be leached or made mobile in some form that it can enter the food chain. I'm drawing a complete blank. The cynical part of my brain just believes that this is an end run around to get coal plants to shut down. Hit the fuel, kill the plant. However that is a part of this thread that doesn't really need to be discussed here, maybe over in current events.