Glazes have historically contained heavy metals, and this is one area where a specific claim is worth more than a general reassurance.
Why They Were Used
Lead lowers the temperature at which a glaze melts and produces a bright, smooth, glossy surface. Cadmium gives strong reds, oranges and yellows.
Both work well, which is why they were standard for a long time.
Both can leach out of a fired glaze into food, particularly acidic food, and both are harmful. Lead is of particular concern for children and in pregnancy, with effects on neurological development.
What Regulation Requires
- Limits on how much lead and cadmium may leach from food-contact ceramics
- Testing against defined standards, using acidic solutions
- Enforcement by food safety authorities in most countries
- Which means compliant commercial dinnerware is tested
- And the risk sits mainly outside that system
Where a range states that materials are tested for daily food contact, of the kind claimed at https://famiware.net/, the useful follow-up is which standard was tested against, since a named standard can be checked and a general claim cannot.
Where the Real Risk Sits
Not with mainstream new dinnerware from a regulated market.
Antique and vintage ceramics, which predate the limits. Handmade or craft pieces from producers who may not test. Imported decorative items sold as ornaments rather than tableware. Highly decorated pieces where the decoration is on the food surface rather than under the glaze.
And any piece where the glaze is damaged, since a crazed or worn surface can release more than an intact one.
The Practical Rules
Treat anything marked decorative or not for food use as exactly that.
Do not use antique or unknown-origin ceramics for acidic food, hot drinks or daily use, particularly for children.
Retire pieces where the glaze has crazed, worn through or chipped on a food surface.
Home Test Kits
Widely sold, and they detect surface lead rather than measuring leaching under standard conditions.
A positive result is worth acting on; a negative one is not a certificate.
Ask for the Standard
A named test is information; the phrase lead-free on its own is not.
Buy From Regulated Sellers
Which is most of the answer.