The risks associated with lead poisoning stem from soluble organic lead compounds entering (or being formed in) the body. Elemental lead does not readily form these compounds when it is in "lumps" such as bullets or pellets, even if ingested whole. Very finely divided lead does react to form soluble organic compunds more readily and it is here where the risks are.
Finely divided lead is generated by abrasion of skin against bullets or pellets so handling these can leave fine lead on the skin. Wash your hands after handling lead, and particularly before eating or smoking. Most bullets have a coating of wax or other lube which provides something of a barrier between skin and the lead itself. Many muzlzle loading balls and airgun pellets have no such barrier layer.
The other major source of finely divided lead for shooters is on indoor ranges. The heat and pressures created inside the chamber cause some of the lead to vaporise and this rapidly condenses into very fine particles as the gasses exit the barrel. This is particularly hazardous as inhalation of same will deposit very fine lead particles in the lungs where they enter the bloodstream. This is why indoor ranges shouhd have forced ventilation flowing down the range and away from the shooter. That grey dust which is found in all indoor ranges is fine lead particles which have condensed out from the muzzle gasses. This is also the source of that hard grey deposit found inside moderators. So when shooting on an indoor range allow a little time for those particles downrange to settle out or be swept away by the ventilation. I do not believe thast airguns generate much in the way of lead vapour except when impacting hard surfaces such as in pellet traps but this will condense and settle rapidly, presenting more of a contact hazard than an inhalation hazard.
Do not eat on the range. Do not smoke on the range. Wash your hands after shooting as they will pick up this dust when changing targets or moving items about the range.
Lead casting has obvious risks from lead vapour. Ventilate well and preferably in the open air.
If soluble lead compounds enter the body they will migrate to the bone marrow and remain there for a very long time so the body burden is cumulative.
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