lead-glazed pottery Behind that pretty glaze, a hidden danger.

Potters’ use of lead is still a problem

New study reveals that lead levels remain high, and pottery is a major cause

The next time you serve up sliced limes to accompany a meal of tacos, beware the bowl you put them in.


Mexican potters continue to churn out products with a lead glaze, a 400-year-old practice that can have extremely harmful effects, particularly for children. The problem with the limes is that a lead glaze and acidic foods don’t go well together: the acid draws out the lead, contaminating the food.

Awareness of the danger of lead glazes has been around for a long time, and there’s even a regulation that prohibits its use. But as with many other rules and regulations, laws and legislation, it goes unenforced.

In November, the journal Annals of Global Health published the results of a study that reviewed articles published from 1978 to 2010 that contained blood lead level (BLL) data in the Mexican population. In the absence of any kind of formal testing program, the study, Blood Lead Levels in Mexico and Pediatric Burden of Disease, offers the only comprehensive research available.

There was some good news in the results: BLLs are down since leaded gasoline was phased out in 1997. However, levels are still very high at 5.36 ug/dL (micrograms per deciliter of blood), and that was in urban areas. Numbers for rural areas are expected to be much higher. (Prior to the prohibition of leaded gasoline, the study found BLLs in Mexico were 8.85 ug/dL in urban areas and 22.24 in rural ones.)

Testing conducted in Morelos in 1996 found average BLLs of 8.2 in children but some individual cases recorded measurements as high as 15. And for the artisanal potter it’s worse — as high as 20 ug/dL.

In the United States, 5 ug/dL became the upper limit in 2012 for children under six after it was reduced from 10.


What does this mean in health terms? The study’s analysis of the possible effects of the lead exposure concluded that more than 15% of the population will experience a gradual decrease of more than five IQ points. When BLLs get up to around 35, IQ loss can be as much as 10 to 20 points.

If that’s not bad enough, lead has also been linked to other issues such as cognitive impairments and attention capacity.

So what do the potters think of all this?

Not a lot. A lead-free glaze will work on small pieces, according to potters spokeswoman María Angela Ortiz Santamaría of Tlayacapan in Morelos. But on larger ones such as cooking pots the glaze isn’t shiny enough and people won’t buy them. “We did it once and lost almost 40% of our production,” she said.

Ortiz said they tell their customers that they should fear teflon instead because their forbears never used to get cancer. “We’ve always cooked in earthenware pots and nothing has ever happened,” and offered the opinion that other dangers were posed by the chemicals used on vegetables and in poultry production.

Changing attitudes and understanding around the use of lead has been the subject of efforts by the American non-governmental organization Blacksmith Institute in collaboration with Fonart, the Mexican government agency charged with promoting artisans and their products. But by all accounts, they’ve made little progress.

However, a new glaze has been developed that might change things. There had been an alternative to lead-based glaze but it required a higher temperature — 1,200 C — than most traditional kilns can provide.

The relatively new boron-based glaze can be fired at traditional temperatures and while some potters have been impressed with the results, less than 100 have made the change. According to estimates there are probably 40,000 active potters.

One other health effect with some current significance has been identified, says the Blacksmith Institute: correlations have been made between successful lead-reduction efforts and a decrease in violent crime.

Another reason, perhaps, for encouraging the use of the new glaze, as if another were needed.

Sources: El Universal (sp)

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