Thanks for your input! Has been a topic which I have been researching recently as well. Bought some maybe-antique cups
I think the largest threat is for "normal" people, with "normal" ware.
For example, people mix tea with spoons, use utensils, that means heavy wear and tear, people eating off the ware and wearing the glaze out, using dishwasher,scraping ware with heavy scrubbing, chipping with heavy use, etc.
No one is going to die from using an antique cup once a year for a special tea ceremony.
But i stay away from antique and pseudo antique ware for daily use.
The problem is also that a lot of the kilns are old and not serviced right, so even if the glaze is ok, there is contamination in the kiln itself, and sometimes, when the manufacturers mix pigments improperly or transport in used and old containers, you get heavy metals.
Lead is very popular in glazes in China because it is the cheapest, simplest flux. Glass ( for the sake of simplicity, Silica ) melts at very high temperature, so you need to add flux to help it melt in the kiln.
Lead is a traditional flux used for thousands of years, it is the best, cheapest flux, very easy to use.
Only way to make lead glazes safe is with proper mixing, firing and testing.
That is expensive...
I love using lead in my glazes, especially raku, but because of health concerns, I stopped using it 20 years ago.