OK.. I use to work for an environmental engineering firm...we delt with a lot of water pollution issues..

According to Perry's Chemicle Handbook.. Lead as a metal is insoluable in water. Certain Lead Salts are (Lead Oxide)..but to a degree where it would take a like a billion years for that 2" cunk of pencil lead that I lost up on the Sky to leach into the water..

On the OTHER hand.... if there are lots of Nitrates loating around in the water, as a result of Agriculture and Lawn fertilizer run off, Cows $H1tting in the river, etc... you can get these nice litte Lead Nitrates forming... which are VERY soluable in water. And are a good way to poisen a river system.. They have a lot of problems with Lead Nitrates leaching out of old mines in the Rocky Mountains... Hence all the crapped up streams in the Rockies. (laugh every time I see a Coors ad, talking about pure Rocky Mtn. water.)

So anyways.. This is yet another reason to try and protect out waterways form Industrial and Agriculture pollution..

I would worry more about the Nitrates than the lead...