Heavy metals in ceramic glaze can pose a risk to health

Coloured glazes of ceramic kitchenware may contain heavy metals like lead or cadmium. On contact with food, these toxic substances may be released from ceramic to varying degrees. The amounts of lead and cadmium which migrate from the ceramic to food is dependent not only the quality of the glaze but also more particularly on the temperature at which the ceramic was fired, the type of food and the duration of contact. The European Directive, which regulates the release of lead and cadmium from ceramics, is currently being reviewed. This prompted the Federal Institute for Risk Assessment (BfR) to re-examine the valid maximum levels. BfR President Professor Dr. Dr. Andreas Hensel comments, "Risks to health from extreme lead uptakes from food stored for longer periods in lead-permeable ceramic containers cannot be completely ruled out today either." Even if the current provisions are complied with, there may be circumstances under which heavy metals may be released into food at levels which, particularly in the case of lead, can no longer be considered safe. BfR, therefore, recommends lowering the statutory maximum levels for the release of lead and cadmium from ceramic objects. Consumers should not store foods for longer periods in ceramic containers.

Up to 4 milligram lead per litre (mg/l) may be released from ceramic containers which make full use of the permitted release level for lead. Depending on the calculation model, lead uptake may considerably exceed the provisional tolerable weekly intake (PTWI) of 0.025 mg per kilogram body weight and week derived by the World Health Organisation (WHO). “Even if it can be assumed that stipulated levels are not exceeded to this high degree every day or lifelong, these are additional and, above all, avoidable exposures“, commented Hensel.

According to BfR the same applies to the heavy metal cadmium whereby the PTWI of 0.007 mg/kg body weight and week is exceeded to a far lower degree. Nevertheless, there are groups of persons who almost reach the limit value for cadmium because of their eating habits and lifestyle. Any additional intake, like for instance from ceramic kitchenware, should, therefore, be avoided. The Institute comes to the conclusion that if the current maximum levels are maintained for the migration of lead and cadmium from ceramic objects to foods intake levels may be reached in individual cases which, especially in the case of lead, can no longer be considered safe. It is not clear how many and how often consumers are affected by high heavy metal intakes of this kind. Particularly with regard to the sensitivity of children, BfR recommends lowering the maximum levels for the release of lead and cadmium from ceramics.

Lead is a naturally occurring heavy metal which is widespread in the environment, not least because of industrial processes. It ranks amongst the strong environmental toxins and accumulates in the organism. Lead is present as an admixture in numerous products like batteries, some paints, glazes down to cosmetics. When ceramics are used normally, it is unlikely that the maximum possible lead amounts are taken up daily or even lifelong. However, if sour foods in particular are stored for longer periods in heavy metal-permeable ceramic containers, the lead amount released may reach critical levels. There are incidences of lead intoxication from fruit juices stored in lead-permeable ceramic jars even today.

Acute lead intoxications manifest themselves through symptoms like vomiting, intestinal colic, constipation down to kidney failure. Children are especially at risk as the developing body reacts even more sensitively to lead. In children elevated lead exposure can lead to irreversible neurological damage including disruptions of brain functions. Chronic intoxications go hand in hand with weakness, loss of appetite, nervosity and weight loss.

Like cadmium, lead is a heavy metal which is widespread at low levels. Cadmium and its compounds, as dust and in aerosols, are classified as carcinogenic substances. Aside from batteries, the metal is mainly used in coloured pigments and for the production of plastics. Cadmium also accumulates in the body via the food chain where it builds up in the liver and kidneys. Once it has been taken up by the body, cadmium is only eliminated very slowly.

Cadmium intoxications initially manifest the symptoms diarrhoea and vomiting. They may lead to liver and heart damage, kidney and circulatory failure. At low doses over a longer period, they go hand in hand with non-specific symptoms like exhaustion, headaches and neurological disorders.

Further information on this subject can be accessed on www.bfr.bund.de under Commodities/Materials in contact with foods.

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