Love fish? Then you probably don't want to read this

Do you know you could be eating fish that has formalin, a preservative that causes cancer? Recently, Kerala food safety department officials seized nearly 9,600 kg of fish preserved in formalin at a border check post in Kollam district. The seized fish included 7,000 kg of prawns and 2,600 kg of other species. The seizure was part of Operation Sagar Rani launched by the state last month. Toxic fish has been seized not only in several other parts of Kerala but in other states too.

Recently, a video shared widely on social media claimed fish sold in markets located in the coastal belt of Karnataka were laced with poisonous chemicals. Formalin-laced fish weighing more than 5,280 kg were seized in Kohima Nagaland this month. These were imported from Andhra Pradesh. Early this month, Kerala officials seized and returned 6,000kg sardines brought to Edappazhanji fish market in Thiruvananthapuram from Hyderabad after they tested positive for high formalin content.

In March, a team of scientists and students of Patna University's zoology department randomly collected samples of dead fish from different city markets and found all of them had formalin.


What is formalin?
Formalin is derived from formaldehyde which is a known cancer-causing agent. It is used to preserve bodies in mortuaries. It can also increase shelf life of fresh food. While fromalin can cause nausea, coughing and burning sensation in eyes, nose and throat in the short term, it can cause cancer if consumed over a long period of time.

Why is fish laced with formalin?
Fish is a highly perishable commodity. If it isn’t maintained at the proper temperature of 5 degree Celsius, it gets spoilt. To avoid that and increase its shelf life, the sellers now use chemicals such as formalin and ammonia. If the point of sale is far from the place of catch, formalin is used as a preservative. Meanwhile, ammonia is mixed with the water that is frozen to keep fish fresh.

How to find if your fish is toxic?
A few scientists of Central Institute of Fisheries Technology have devised an “easy, efficient and inexpensive method” to test if the fish have been adulterated. The working principle is similar to a litmus test. A paper strip is rubbed on the fish’s surface and then a drop of reagent, which contains several chemicals, is added to it. The paper will change colour depending on the adulterant. If formalin is detected, the white paper strip will change to blue in 30 seconds and depending on the content of ammonia, it will change to green or blue in two minutes.