Micro-plastics in the fish I eat

Researchers from the Indian Institute of Science (IISC) found out that pollutants like micro-plastics may be causing growth defects in fish, including skeletal deformities

The other day, as I stepped out of my car to buy fish from a fisher folk on the bank of river Mahanadi, a waste carrier vehicle engaged by the local Municipality rushed towards me in high speed. It would have killed me had the fish seller not shouted to warn me about the incoming danger. Saved from the road accident, as I walked on to buy my favourite Rohu fish, fresh from river Mahanadi, I hardly had any idea of another danger that stared at me: micro-plastics in the body of the fish. This might not be an immediate danger to my life but is surely a slow-onset disaster posing a lot of threat to not only human health but that of other species, and the ecosystems they are part of. Of course, micro-plastic is not the only pollutant that invades a fish or waterbody. They could be contaminated by heavy metals and other pollutants. In this piece, I am touching upon the micro-plastic menace, that’s growing out of bounds and has already posed a great challenge before all of us.

Fish from the reservoir

A latest scientific study has got me especially worried particularly because I and my family love to have river fishes. Researchers from the Indian Institute of Science (IISC) have, in this study, found out that pollutants like micro-plastics may be causing growth defects in fish, including skeletal deformities, in the Cauvery River. An important aspect of this study was to find out pollution of water from different locations at the KRS Dam with varying speeds of water flow: fast-flowing, slow-flowing, and stagnant. Water speed is known to affect the concentration of pollutants. Such pollutants, including micro-plastics, could impact the health of people and planet. A researcher involved in the above study opines, polluted water can cause diseases including cancer. 

We have all observed that our rivers have changed over the decades, but there is hardly any data to show all the dimensions of these changes. This study, led by Prof. Upendra Nongthaomba, throws a completely new dimension of the change our rivers have faced. He is a worried man as his favourite fish destination gives him shockers. Reports published about this study quotes the professor saying how he cherished going to the backwaters of the Krishna Raja Sagara [KRS] Dam and having fried fish on the Cauvery River bank. Things have changed now as physical deformities have been noticed in fishes, which could be due to the degraded quality of water. Hence the study. 

Dammed rivers, unhealthy fishes

What Prof. Nongthaomba worries about his favourite fish and its habitat is something that worries me as well: about my favourite fish and its habitat. It concerns me more because the kind of deformities that the professor can see in his favourite fish may not be visible to me. I am not an expert on that, so are other people who relish the fish from my river. 

More so because movement of the fish is restricted by a dam and thus chances of pollutants affecting the fishes are more. 

The fish I bought was sourced from the Hirakud dam. This is the only large dam on the lifeline river of two states – Odisha and Chhattisgarh – which has submerged an area of 746 square kilometres thus creating one of the largest human-made lakes in the world. Besides being used for other purposes, the water in this reservoir has created a huge fish reserve for both fisher folks and traders in Odisha. Thousands of people eke out of fishing in this reservoir on a daily basis. Pollution from coal mines, thermal power plants, steel and sponge iron industries, cities and towns – from the upstream locations in both Odisha and Chhattisgarh enter into this reservoir. There is hardly any study available on the impact of all these pollutants on the water of the reservoir, let alone that on the health of the fishes we eat. That’s the reason the study in the KRS dam worries me further. 

The speed of the flow, which could make a lot of difference to contamination of the fishes, is to be noted specifically. In the first part of the study that Prof. Nongthomba and team did, and in which they analysed the physical and chemical parameters of water samples, the slow-flowing and stagnant sites threw more worrisome results than the other two types of sites. In the places water was flowing too slow or was stagnant, the dissolved oxygen (DO) levels were much lower than they needed to be. Further, water in such sites had well-known bio-indictors of water contamination such as Cyclops, Daphnia, Spirogyra, Spirochaeta and E. coli. They study went beyond this to find out that the wild fishes exposed to slow and stagnant waters were found with skeletal deformities, DNA damage, early cell death, heart damage, and increased mortality.

The researchers found out that these problems in the fishes occurred mostly due to micro-plastics and chemicals. Micro-plastics, used in our households as well as in industrial activities have already penetrated deep into our freshwater and marine ecosystems. Chemicals such as the cyclohexyl isocyanate that are commonly used in both agriculture and pharmaceutical industries, were the other form of pollutant that have impacted the fish samples studied. The impact of eating these fishes for us humans is not yet known completely. The researchers however say long term impacts cannot be ruled out. 

Big dangers of slow moving micro-plastics

Studies have confirmed that dammed rivers post many threats to fish health and diversity. This new study sends new signals to worry about. Earlier, in this column, I have written how our rivers carry huge loads of plastic pollution to the oceans. Globally there has been much talks on the plastics in the oceans. 

Contamination of freshwater ecosystems due to plastics, especially micro-plastics, is yet to pick up the way it should have. 

That perhaps because people think these ecosystems, especially rivers, have worked more as carriers of micro-plastics into the sea rather than being polluted at their own flow and sediment levels. This perception has to change. A new study compels us to do so. 

In what’s being called the first of its kind study, researchers from the Northwestern University and the University of Birmingham in England dug out something called hyporheic exchange. This is a process in which surface water mixes with water in the riverbed and thus can trap lightweight micro-plastics that otherwise might be expected to float. Trying to find out where do a lot of these plastics from the urban sewer systems and waste dumps go, the researchers have found out that in headwaters, micro-plastic particles moved at an average rate of five hours per kilometer. But during low-flow conditions, these could take up to seven years just to move only one kilometre. That means, during this time, and in these areas, the fishes and other species in the water may ingest micro-plastics and this might degrade ecosystem health. 

Both the above studies try to warn us at least one thing: don’t contaminate the freshwater ecosystems with plastics and other wastes. Micro-plastics contamination of the fishes we eat is certainly not worrying us a lot at the moment because we don’t see a disaster happening to our own health due to this anytime soon. Human brains are tuned to respond fast and get pained more by rapid disasters rather than slow onset ones such as this. However, the slow onset disasters such as consumption of fishes, contaminated by micro-plastics or chemicals, destroy us by a bit on a daily basis. This weakens our resilience to health and environmental hazards, including the ones caused due to climate change. We need to wake up to the deadly cocktail of reducing water in our rivers – due to dams or otherwise – and increasing pollution.