I have always been told that once fired to a smooth surface
they are entirely non toxic. Like asbestos or lead based
paint, the problematic chemical contained within enamels is
only dangerous when the enamel is a powder and can become
airborne or the lead is free to be absorbed by touch.
Mostly that’s true. The exception would be enamelware that’s
designed for food use, or other environments where there may be
exposure to acidic environments. These (such as fruit juice,
etc.) can leach the lead content back out of the glass (enamel).
Same is true of lead based colors in ceramic glazes. It’s
prehaps helpful to remember that while lead lowers the fusing
temp of the enamel, as well as increasing the refractive index of
the glass, thus making the enamel more “brilliant” and glassy, it
ALSO lowers the hardness and durability of that enamel. Recall
how fine leaded crystal will etch some when washed with harsher
dishwasher detergents, while ordinary glass will not do so as
Hope this helps.