RINSING the dishes meticulously may be a mistake since it could get rid of valuable chemicals in the detergent, according to an Australian public health specialist.

Conor Reilly, head of the school of public health at the Queensland University of Technology, says that in Tasmania, detergent residues left in milk containers were found to add a chemical containing iodine to children's milk, and resulted in a reduction in endemic goitre, a condition caused by iodine deficiency. Similarly, the tin used in food cans and stainless steel saucepans has been found to make up for a deficiency of chromium in children's diets.

Mr Reilly warns in a report in New Scientist that an obsession with the purity of food means essential trace elements are being lost from the diets of Western societies.