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Malachite green in aquacultured fish

(Last updated December 2005)

In mid-2005, Food Standards Australia New Zealand (FSANZ) led a national survey of chemical residues in fish produced by aquaculture. Food regulatory agencies in all Australian States and Territories participated as part of the newly developed Coordinated Survey Plan. Of 56 antimicrobials and other chemicals examined, the only chemicals detected were malachite green and/or its metabolite, leucomalachite green, which were present in ten of the sixty samples taken. At the levels these residues were found in fish, the public health and safety risk is considered to be very low. However, malachite green and its metabolite are not permitted in fish sold in Australia for consumption.

What is malachite green?

Malachite green is a synthetic dye used to colour fabric and paper. It is also used to treat fungal and protozoal infections of fish and fish eggs. It is not registered for use in aquaculture and the Australia New Zealand Food Standards Code does not allow malachite green residues to be present in fish sold for human consumption.

Is malachite green harmful?

FSANZ has completed an assessment of the potential public health and safety risk posed by malachite and leucomalachite green residues in Australian farmed and imported fresh fish. Malachite green has been tested in long-term studies in experimental animals – in these studies, there is some equivocal evidence of carcinogenicity in mice at high dose levels. The available data do not indicate that malachite green presents a carcinogenic risk for humans. At the very low dose levels detected in fish (less than 0.14 milligrams per kilogram), the public health and safety risk is considered to be very low.

Why did FSANZ conduct the survey of chemical residues in farmed fish?

Prior to the survey, several overseas food regulators had reported the presence of unapproved antimicrobial chemicals in aquacultured fish. To examine the situation in Australia, all States and Territories participated in a national survey managed by FSANZ. The aim was to determine if antimicrobial residues and other substances were present in local and imported aquaculture products.

How was the survey conducted?

FSANZ conducted a tender and appointed a suitably accredited laboratory to undertake the analytical survey of aquacultured finfish. Food regulatory agencies in all States and Territories collected a total of sixty fish samples from around Australia. These samples represented the aquacultured fish available for consumption in Australia from late April until late June 2005. The laboratory tested for over fifty substances and their metabolites, including nitrofurans, chloramphenicol, sulphonamides, tetracyclines, malachite green, penicillins, macrolides, trimethoprim, quinolones and polychlorinated biphenyls (PCBs). Additional testing for a range of heavy metals and nutrients is currently underway.

What were the results of the survey?

The only antimicrobial residues to be detected were those of malachite green and/or its metabolite leucomalachite green. The residues were found in a total of ten samples – three out of the nineteen fish samples grown in Australia and seven out of the forty one imported fish samples. The levels detected were less than 0.14 milligrams per kilogram. The rate of non-compliance was similar for both domestic and imported fish.

What action are food regulators taking?

In those States or Territories where malachite green residues were detected in domestically farmed fish, further investigations are being conducted to determine the scope of malachite green usage in the industry, including taking additional samples.

FSANZ is also working closely with the jurisdictions and the Department of Agriculture who have taken appropriate follow-up investigative and enforcement actions to ensure that aquaculture businesses and fish available for sale complies with the provisions of the Australia New Zealand Food Standards Code. As of 26 September 2005, The Department of Agriculture (formerly AQIS) have initiated random testing for malachite green in imported aquacultured fish.

 

 

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