Mexico is set to publish a revised standard on lead in glazed pottery this year, as part of a plan to control the toxic metal’s presence in consumer products.
Pottery in Mexico is typically fired at low temperatures and coated with a glaze made of lead and other minerals. Lead has been the preferred choice for artisanal potters for centuries, because it will fuse at much lower temperatures than alternatives require.
The negative health effects of this practice were highlighted in a 2017 study, which found that around 200 micrograms per litre (?g/L) of lead leached from pottery into the food and water cooked and stored within it. The US banned pottery imports from Mexico that aren’t labelled ‘lead-free’ two decades ago.
But despite efforts by NGOs and the government to encourage lead-free substitutes, pottery has been flagged in the Mexican health authority’s national chemicals policy proposal as “one of the [population’s] main sources of exposure to this heavy metal”.
The health authority says “research currently available nationwide” estimates that one million Mexican children under the age of five have lead poisoning, according to the health authority. This equates to one in 11 children under five in the country.
The 2016 standard on glazed pottery currently in place sets maximum migration limits for lead, ranging from 2 milligrams per litre (2mg/L) for small hollow jars to 0.5 mg/L for pieces that will come into contact with food or drinks.
But this standard is “useless and ineffective”, according to Sofía Chávez Arce, director of the NGO Casa CEM, because it sets migration limits instead of total lead content limits, which “might” protect the end user, but won’t help the workers involved in manufacturing, or their families and surrounding communities. Additionally, with tens of thousands of artisanal family pottery shops in the country, “surveillance is impossible”.
The government is also battling with a long-established tradition. It has tried to promote a boron-based alternative to the lead glaze, but many potters still prefer lead.
The health authority’s proposal did not outline what its new standard or law will look like, but said it expects to publish it this year. Ms Chávez says it should set limits for total lead content in pottery instead of migration limits, and it should address the lead oxide supply chain that supplies the trade.
Several different standards regulate lead in consumer products in Mexico (see box), but there is no overarching law or regulation.
“I think all lead limit standards should be reviewed for inconsistencies … and set into one comprehensive law,” Ms Chávez said. “As of now they are very confusing, some [are] obsolete and some contradictory.”
A lack of surveillance and enforcement are also massive problems, she added.
Pottery is the health authority’s first priority, followed by updating standards on lead paint used in children’s toys and games and then paint used in homes, according to its proposal.
The proposal also sets out plans for a national chemicals law that would place the burden of proof on companies to show substances they import or use in the country are safe, and would allow the government to restrict or ban those that pose an “unacceptable risk”.
Lead in consumer products
A number of Mexican standards have been set for lead in consumer products in recent years, including:
NOM-003-SSA1-2006, published 4 August 2010: prohibits paints with a lead content higher than 600 parts per million (ppm), and sets out labelling requirements for leaded paints;
NOM-252-SSA1-2011, published 15 May 2012: sets migration limit of 90 mg/kg for lead in toys and school supplies, as well as limits for other heavy metals;
NOM-004-SSA1-2013, published 2 May 2014: says the use of lead compounds “should be avoided” in paints, coatings, inks, glazed pottery and cosmetics.
NOM-231-SSA1-2016, published 25 October 2016: sets migration limits for lead and cadmium in pottery. For lead, limits range from 2 mg/L for flat pieces and small hollow jars to 0.5 mg/L for pieces that will come into contact with food or drinks.
Chemical Watch, 16 April 2020