Food Safety Focus (5th Issue, December 2006) – Food Incident Highlight

Malachite Green Found in Freshwater Fish

With the recent concern over veterinary drug residues in food, the CFS had stepped up surveillance on freshwater fish in local markets for the presence of malachite green (MG) and several other veterinary drug residues. Of 17 freshwater groupers tested, 13 from untraceable sources were found to contain MG. The CFS had maintained close liaison with the Mainland authorities over the issue.

Under the current administrative arrangement, freshwater fish exported from the Mainland to Hong Kong should come from one of the registered fish farms and should be accompanied with health certificates. With the registration system in place, the source of the affected fish could be effectively traced.

MG is a synthetic dye used to colour materials such as cotton and paper. It had been commonly used worldwide in aquaculture as early as 1930s because of its effective antifungal properties. It had been used for treating parasitic, fungal and protozoan diseases in fish. One of the MG metabolites, leucomalachite green, would persist in fish tissues for a long period of time. With the legislative amendments in place since August 2005, MG should not be present in any food sold in Hong Kong .

Based on the levels of MG and/or nitrofurans residues found in the affected fish samples, usual consumption of the affected fish is unlikely to pose significant health risk. The public is advised to maintain a balanced diet.