Several metals are toxic and if ingested in sufficient quantities can give rise to food poisoning. The symptoms, mainly vomiting and abdominal pain, usually develop within an hour. Diarrhoea may also occur. Metals may be absorbed by growing crops, or contaminate food during processing. Acid foods, such as fruit, should not be cooked or stored in equipment containing: antimony (enamel coatings); cadmium (refrigeration apparatus); cooper (pans); lead (ceramics, earthenware and lead crystal) or zinc (galvanised metals). Soft water may absorb lead from old pipes.
Tin and Iron
Acid foods may also cause problems if stored in tin-plated iron cans for too long. The acid foods react with the tin-plate and hydrogen gas is produced. Iron and tin are absorbed by the food which may become unfit for human consumption.