HEALTHNET

What is Malachite Green?

Malachite Green (MG) is a synthetic chemical commonly used as an industrial dye. The name comes from the similarity of its colour to the semi-precious stone malachite.

(Posted on 15 September 2005)

What is Malachite Green?

Malachite Green (MG) is a synthetic chemical commonly used as an industrial dye. The name comes from the similarity of its colour to the semi-precious stone malachite.

The chemical has potent anti-fungal and anti-parasite activities, and has been widely used in fish farms and hatcheries to treat external fungal and parasitic infections. It is both cheap and effective. When added into the water, it penetrates deeply into fish body tissues. Prior to the 1990s, it was just part of normal business in aquaculture everywhere.

MG is converted to Leucomalachite Green (LG) once inside the body of the fish. LG is a lipophilic chemical, which means that it tends to be concentrated in fatty tissues. This partly explains its effectiveness as a drug in water, but the same quality also accounts for its toxicity. Like many environmental toxins, nature has not yet evolved a way to get rid of the industrial chemical, and it stays in the fish indefinitely.

Use of Chemicals in Fish Farms

The past few decades have witnessed the depletion of most wild fisheries. Farmed fish and shellfish now supply over 30% of all the seafood consumed worldwide today and fish farming has become a competitive business. Drugs and chemicals are used widely, and are not effectively controlled, as stated in a report from the National Academy of Sciences in 1991. Different countries also have different standards and different lists of approved drugs for use in fish farms. The U.S., for example, approves of the use of the antibiotics Terramycin, Sulfamerazine, orometopum and sulfadimethoxine as well as the fixative parasiticide formalin and the anesthetic Finquel. Europe approves over 15 drugs and Japan 24. MG is still extensively used, especially in less developed parts of the world.

Can Malachite Green cause cancer, and why the fuss now?

There is no solid evidence that MG can cause cancer in human beings. In recent years, however, scientists have used more sophisticated methods to test for DNA adducts in cultured cells to measure a chemical's potential to damage our genetic material. It was found that both MG and LG can induce DNA adducts in liver cells of rats. This finding, together with the fact that the chemical structures of MG and LG are similar to other known carcinogenic dyes, such as gentian violet, makes regulatory agents more wary towards MG in our food chain.

The Department of Health in the UK therefore concluded that both MG and LG are "potential in-vivo mutagens" in 1999 (The US has banned its use since 1991 and Canada in 1992). In 2002, China also banned the usage of malachite green in food production. However, the chemical might still be added to tanks or used as disinfectants as the fish is transported.

Aquaculture has become the fastest-growing food industry and a competitive global business. Apart from health risks to guard, and there are interests to protect. As laboratory methods to detect traces of MG and LG are more available, some countries have started to test for the chemical in imported farmed fish. News that food products containing traces of MG and LG, sometimes from developed countries such as Britain and Canada, have repeatedly hit the headlines.

Have my health been affected by eating tainted fish?

It is highly unlikely to accumulate enough MG from fish in the diet to reach toxic levels (unless, as Dr. York Chow said, one takes more than 290 Kg of tainted fish a day). However, adverse effects of environmental toxins from various sources might add up to affect our health in future. After all, the cause of cancer is multi-factorial, and such should also be our approach to the prevention of cancer. Avoid suspected carcinogens in our diet as much as we can afford-better safe than sorry.

Source: Quality HealthCare