In article ,
Charles Spitzer wrote:

neither the glaze nor the tile may be safe. there's a lot of glazes that
aren't food safe (contain lead, cadmium, etc) and could leach metals from
either a basic or acid solution in contact with it. you'd have to find out
what is in them from the manufacturer, and they probably don't know since
tiles typically don't have a msds.

Anybody selling a kitchen tile laced with toxic heavy metals is just
asking for litigation...