I used to have a link to a study on pollution from lead fishing weights lost in rivers, can't seem to find it right now. Anyway, it said the main concern was waterfowl ingesting small weights like split shot. At the temperature of river water the lead dosn't disolve into the water and was not an environmental problem.

Looking for something to worry about? Look here.
http://www.oregonlive.com/news/oregonian...93220242139.xml