Acute copper poisoning

Copper was once a favoured metal for food containers and cooking utensils. Its high conductivity facilitated rapid heating and led to its use in kitchenware as well as in kettles and pans used, for instance, by jam makers. The copper was usually tin-plated as even trace amounts of copper can lead to oxidation and discolouration problems in a wide range of foods.

For those reasons, as well as the potential toxicity of copper, it was replaced by other materials notably stainless steel in processing operations and aluminium and stainless steel in kitchens. The Australian Food Standards Code places a upper limit of 5.0 mg/kg of copper in beverages and other liquid foods and 1.0 mg/L in water.

A letter published in the Medical Journal of Australia, 17 May 1999, shows that care must still be taken to avoid copper in domestic or near domestic situations. The journal correspondents describe an incident in Western Australia in which 15 children suffered what appears to have been acute copper poisoning characterised by vomiting and nausea.

The children became ill after drinking lime cordial which had been prepared the night before in an old urn. The children developed symptoms within minutes of drinking the cordial and recovered within an hour.

Analysis of the lime cordial which was still in the urn failed to reveal the presence of any pathogenic microorganisms but it did reveal a copper concentration of 300 mg/L. Since acute poisoning can occur with oral ingestion of 10-30 mg of copper in copper salts, even a small intake of the lime cordial could have led to the symptoms observed.

The correspondents draw attention to the danger of using old urns for preparing acidic drinks if a copper element is still in the vessel.

Food Safety and Hygiene
Prepared by Keith Richardson and Beverley George
Food Science Australia
PO Box 52, North Ryde 1670. Tel +61 2 9490 8397 Fax +61 2 9490 8499