The effects of the vinyl paint fumes can be horrible in short-term, the thinners are common with many of the thinners in aerosol type spray paints along with some other extremely nasty contents.
If your dipping one jig at a time from a small jar.. it will take a while, but you will eventually feel the effects. Mass dipping with larger quantities exposed will hit you faster, and 10 times harder. Without proper ventilation, or anything malfunctioning in your respirator equipment.. you will be *high* enough where you will actually have to think about breathing to do it properly after moving away from the chemicals.
Long term effect there is nervous system issues… Lack of feel(touch, impact, etc), amongst endless other possibilities of damaging your nerves.
Lead has its own list of issues which can be easily looked up on the internet… but dont stop at lead, be sure to look up Linotype poisoning, and any other common ingredient in *lead*. Most lead is nowhere near pure lead. It can poison you, cause health issues short and long term. One has to use great care if working with lead regularly. Common sense would say that one not exposed often for long periods of time shouldnt have the same ill effects of a person working with it regularly for years.
Most any chemical can be harmful. The amount of exposure makes a huge difference. Nobody thinks of gas fumes being bad because we only smell them while filling our gas tanks at the station… we would think of it differently if we were working at the refinery constantly exposed to higher than normal concentrations of the product.
As I said earlier.. I am not trying to scare anyone from making jigs… just be sure to use some extra precautions even if it seems excessive. A $50 respirator can go a long ways.