South Africans are potentially being exposed to pottery and ceramics that are coated in glaze containing lead, a toxic heavy metal which can damage multiple organs when consumed, according to a team of scientists, including from the South African Medical Research Council (SAMRC).
It is estimated about 7.8m children in South Africa under 14 have lead poisoning, which is about 53% of all young people in that age range. This means they have more than five micrograms of lead per 100ml of blood, the clinical threshold for lead poisoning set by the National Institute for Communicable Diseases.
SAMRC scientists have found several sources of lead exposure over the past two decades, writes Jesse Copelyn in Spotlight.
These include lead-based paints (which can chip and generate lead dust, which is then inhaled), certain traditional ayurvedic medicines that contain lead; fishing sinkers (which are sometimes melted down, producing toxic fumes); lead ammunition (which can generate lead dust when fired, and may contaminate hunted game meat), and gold mining waste facilities, which can contaminate the surrounding soil.
The recent paper on ceramics, published in the journal SciELO (Scientific Electronic Library Online SA), adds to a growing body of evidence that cookware and crockery may also play a role.
Toxic pottery
Research for the paper was conducted in 2018 when SAMRC scientists bought 44 randomly selected plates and bowls from six large retail chain stores in Johannesburg. After testing the glaze, they found almost 60% of the items contained more than the maximum amount of lead recommended by the UN, which is 0.009% of total content.
The average item contained about 47 times this amount.
Glaze is a liquid coating applied to ceramics to make them shinier and more durable. Once coated, the ceramic is fired, leaving it with a glossy sheen.
Lead is often used in the glazes to add extra colour and increase water-resistance, but if the ceramic isn’t heated at a high enough temperature, the glaze won’t completely solidify.
In the case of ceramic crockery, this means lead may run off into food or water prepared in these dishes, particularly if they are used for cooking or holding acidic foods.
This is what has happened throughout parts of Mexico, where children have higher amounts of lead in their blood if they live in households where food is prepared in lead-glazed pottery, a result which researchers have found repeatedly.
To test whether lead is leaching from the South African ceramics, the SAMRC researchers left an acidic solution in the plates and bowls. When they returned 24 hours later, elevated lead levels were found to have run off one of the items.
Angela Mathee, head of the SAMRC’s environment and health research unit and the paper’s lead author, said: “Our concern is that particularly for people who keep their ceramic ware for a long time, with knocks and cracks and wear and tear over the years, it’s possible the product could start leaching, even if it weren’t at the time of purchase. This is untested.”
A second caveat is that of the 44 bowls and plates, only one was originally made in South Africa, and it is this item that released lead.
Additionally, even if lead-based ceramics don’t leach, the production of these items may still cause harm
The African-made piece of crockery had a coating containing more than 100 times the amount of lead legally permissible under a 2009 law, despite the tests being conducted nine years after it was passed.
The Mexican solution
In Mexico, a ban on lead glaze has long gone unenforced, but NGOs in parts of the country have responded by assisting artisanal potters to switch to lead-free glazes and to develop higher-temperature kilns to prevent metals from leaching.
This has been coupled with public awareness campaigns about the harms of lead-based pottery and a certification programme for potters using lead-free coatings.
Though this is the first time lead has been found in ceramic glazes in South Africa, other kinds of kitchenware products have previously been shown to contain lead. In 2020, researchers published a study in which they bought 20 cooking pots from informal traders and artisanal manufacturers across the country. Each pot was made from recycled aluminium.
They found lead in every pot, and some also contained dangerous amounts of arsenic – a known carcinogenic. The researchers cut up the pots and boiled a piece from each one in an acidic solution.
They found 11 out of the 20 pieces leached more lead than the maximum permissible limit set by the EU. The experiment was repeated twice more on the same metal pieces with similar results.
The authors concluded that artisanal aluminium pots are a possible source of lead exposure in the country. The issue may extend past individual households, as the SAMRC has documented the use of artisanal aluminium pots in school feeding programmes.
Are regulations on lead being ignored?
South Africa has already taken legislative steps to deal with lead coatings. In the 2000s, alarming studies found lead-based paints covering homes and playground equipment in public parks across several cities. In response, a law came into effect in 2009 that made it illegal to sell household paint or glaze that is more than 0.06% lead.
Draft regulations published in 2021 will further slash this limit to 0.009% in line with recommendations by the UN. These will only become enforceable once the finalised regulations are gazetted.
See more from MedicalBrief archives:
Lead poisoning still a serious threat but no plans to address problem in SA
Lead pollutants more harmful than thought – Norwegian/Columbian study
Lead bullets at shooting ranges a health risk, should be phased out