Lead was banned from Shotgun shells years ago and maybe it makes sense to do the same for weights?
Not really. There is lots of lead in shotgun shells. You just aren't permitted to use lead shot in shotgun shells when hunting migratory waterfowl because the lead shot settles in shallow bodies of water and is ingested by feeding waterfowl. In most cases you can use lead shot for upland game birds.
As typhoon said, lead in the Fraser isn't a huge risk as waterfowl aren't likely to ingest a 3 oz betty from the bottom of a large, swiftly moving, river.