Malachite Green and Nitrofurans Residues
Found in Freshwater Fish Imported from the Mainland


The Centre for Food Safety (CFS) conducted a survey on a variety of freshwater fish commonly found in Hong Kong. Multiple freshwater fish samples were collected from the local market for analysis of malachite green and several other veterinary drug residues.

Analysis Results and Actions Taken by the CFS

Among the some 70 freshwater fish samples tested by the CFS, 15 samples were positive for malachite green (13 freshwater grouper samples, 1 silver carp sample and 1 mud carp sample). According to the latest results, among the malachite green tainted samples, 4 freshwater grouper samples and the silver carp sample were also positive for nitrofurans residues. So far, chloramphenicol was not detected in all the samples. Close liaison has been maintained with the Guangdong and Beijing authorities to follow up the situation. The export of freshwater fish from the two affected registered fish farms to Hong Kong has been suspended.

What is Malachite Green?

Malachite green is a chemical dye which has been used worldwide in aquaculture for a long period as an antifungal agent. The main concern in food is its cancer causing potential.

In Hong Kong, the maximum level of malachite green should be 0 μg/kg in any food (including live fish) under the Harmful Substances in Food Regulations, Cap.132AF.

What is Nitrofurans?

Nitrofurans is a family of antimicrobial agents which can be used as veterinary drugs. The main concern of nitrofurans in food is that a type of nitrofurans may cause cancer in experimental animals. However, for the type of nitrofurans detected in this survey, there is inadequate evidence that it can cause cancer in humans.

Based on the levels of nitrofurans residues found in the affected freshwater fish samples, risk assessment suggested that the risk to health is low upon usual consumption of the fish.

Advice to Trade and Consumers

  1. Traders are advised to stop the sale of freshwater grouper until the situation has been rectified.
  2. Under the current arrangement, freshwater fish exported from the Mainland to Hong Kong must come from registered fish farms supplying fish to Hong Kong and are accompanied with health certificates. The CFS would mark and seal those imported freshwater fish without health certificates.
  3. Based on the levels of malachite green/nitrofurans residues detected, risk to health is low upon usual consumption of the fish. There is no cause for undue alarm.
  4. The public is advised to maintain a balanced diet.

Further information

Further information about malachite green can be obtained from the following webpages: