Lead is not a hazard as long as it is sealed in the stand. This is one of those environmental alarms that is wildly overblown in many circles. It is a very stable metal which must be ingested in order to cause harm. Short of eating it or inhaling lead dust, it isn't going to hurt anyone. Lead dust inhalation IS a serious health hazard in closed shooting ranges, but most people don't use their listening rooms for target practice. And it was removed from gas for the same reason-- dust inhalation. As an aside, anyone who still has amalgam fillings (lead/mercury) in their teeth is strongly urged to have them removed and replaced with epoxy-- this is a real health threat.
As far as a damping material inside a tube, lead is vastly better than steel shot but not much better than sand. Damping is a function of how much kinetic energy is dissipated as frictional heat, and steel isn't going to absorb much energy at all. Both lead and sand do, though. If you're really concerned about the health risks of lead, use sand, but WEAR A MASK when handling it and then seal the stand-- inhaled free silica is a cancer agent (at least in the case of long-term exposure), and without a mask I would say it's probably more dangerous than just pouring in lead shot.
