I have heard somewhere that the earthenware pots contain lead, which can cause brain-damage.
Is this information correct?
Skeptics Stack Exchange is a question and answer site for scientific skepticism. It only takes a minute to sign up.Sign up to join this community
Traditional glazes used on earthenware pots used to contain lead. This lead can leach out and cause lead-poisoning.
cider allowed to stand in glazed earthenware pots (to make hard cider) was rapidly impregnated with lead
In fact, lead poisoning was known as "Potter's Disease".
However, with the banning (in the US) of lead in glazes the threat is reduced:
The reduction of lead in gasoline, controlling the use of lead pigments in paints and printing inks, and banning of lead-based glazes on pottery and ceramic ware (Wallace et al. 1985) have resulted in a reduction of both industrial and population exposure to lead
However, in 2010, the US FDA released a Consumer Update: Some "Lead-Free" Pottery Can Still Taint Food.
In it, they warn that some pottery labelled "lead-free" may still contain significant levels of lead, because of contamination of old kilns.
Pottery made with earthenware must undergo glazing, a process in which a thin, glass-like coating is applied and fused onto the surface of the clay. This seals the pottery's pores, allowing it to hold food or liquid.
The glaze fuses to the pottery when it is fired in a kiln, a special oven used to bake clay.
“In the past, potters have usually used lead glazes," says Kashtock. "Today, many of the potters in Mexico have switched to non-lead glazes. However, they may be using old kilns that were once used for firing lead-containing glazes."
Kashtock says that while these potters believe they are making a lead-free product, the kilns they are using may be contaminated with lead residues from prior firings of lead glazed pottery. “‘Lead-free’ glaze can then become contaminated during the firing," he says.
It goes on to explain that some glazes containing lead are actually safe, as they do not leach lead into food.