Microplastics in the Ganga River - How Dangerous is the Situation?
Microplastics are recognized as a main source of marine pollution. The plastic products and waste materials dumped in the Ganga River break down and are eventually broken down into micro particles and the river finally transports large quantities downstream into the ocean. Untreated sewage from many cities along the Ganga River’s course, industrial waste and religious offerings add pollutants into the river as it flows through numerous thickly inhabited cities. In this article, Dr Rina Mukherji talks about two recent studies that have revealed the high prevalence of microplastics in the Ganga River basin, and pointed to the risks involved to freshwater biodiversity in the region.
Two recent studies have revealed the high prevalence of microplastics in the Ganga River basin, and pointed to the risks involved to freshwater biodiversity in the region. The first of these studies, “Quantitative Analysis of Microplastics along River Ganga” by Toxics Links, was done by examining the waters of the Ganga River off Haridwar, Kanpur and Varanasi at several points in the respective cities, and documenting the kinds of microplastics present in the waters.
The second study, “Risk Assessment of Plastic Pollution to Migratory Species in the Mekong and Ganga River Basins” done for the United Nations Environment Programme (UNEP) and the Convention on Conservation of Migratory Species of Wild Animals (CMS) examined the waters at several points of the Mekong and Ganga basins. The Toxics Links study in the waters off Haridwar, Kanpur and Varanasi, found 40 different kinds of microplastics, with the composition and prevalence in tune with prevalent industries and activities in the cities and towns concerned. The CMS/UNEP study, on the other hand, went further in actually determining the risks to specific species on the basis of a risk matrix in the concerned river basins of the Ganga and the Mekong.
What are Microplastics?
However, to understand the significance and scope of these studies, especially focussing on the Ganga, which is known to be the second most polluted river in Asia, it is important to know the nature and menace posed by microplastics. Microplastics (MPs) are defined as small fragments of plastics, smaller than 5 mm that make their way into the aquatic and general environment. Microplastics can be either:
Primary: These include microbeads found in cosmetics, personal care products, plastic pellets used in industrial products, and plastic fibres used in textiles.
Secondary: These are formed when larger plastics break down through weathering, wave action, or wind abrasion, weathering and exposure to sunlight.
Since microplastics are not biodegradable, they continue to accumulate in the environment, polluting marine and freshwater ecosystems, and can pose a major hazard to several reptilian, piscean, and avian species. Fish, crustaceans and birds are known to often ingest microplastics floating on the water surface, mistaking them for food. This can result in neurological and reproductive toxicity, ultimately proving lethal. Ingestion of microplastics by smaller species can result in them working their way up the food chain, from tiny zooplankton to the largest predators.
Findings Regarding the Ganga Waters
As per the analysis by Toxics Links, there were 40 types of polymers found in the three locations under study. In all locations, ethylene vinyl alcohol (EVOH), polyacetylene, phenol isopropylated phosphate (PIP), polyvinyl chloride (PVC), and polyvinyl alcohol (PVAL) were found to be predominant.
EVOH is known for the best barrier resistance to gases such as oxygen, nitrogen, and carbon dioxide. This makes it particularly suited for packaging food, drugs, cosmetics, and other perishable products. When compared to other common films, EVOH is considered to have superior barrier properties. Polyacetylene, which is a conductive polymer, has no commercial application but is used as a doping agent in manufacturing electronics and thin films. It is found very commonly. Polypropylene is very commonly used in packaging, plastic sheets, fibre and fabrics, tape, and rope. PIP is mainly used in footwear and baby bottle nipples. Polyamide (PA), commonly known as nylon, is used as a natural fibre and metal wire in clothing and industry. PVC is used in pipes, wires and cables, medical devices, and automotive industry. Polyvinylpyrrolidone (PVP) is used in cosmetics and pharmaceutical industry.
The presence of such a wide variety of plastic resins is indicative of the fact that microplastics in rivers may not come from industrial waste alone, but result from anthropogenic activities such as bathing and washing too. This is evident when we examine the composition of microplastics in the Ganga River.
Haridwar showed the lowest number of MPs/m3 as compared to Varanasi and Kanpur. Within Haridwar, Har Ki Pauri showed the maximum prevalence of microplastics (1.84 MPs/m3), followed by Kankhal (1.77 MPs/m3), and Singhdwar (H5) (1.31 MPs/m3). The reasons are obvious; Har Ki Pauri is the main spot of pilgrimage, where hundreds of pilgrims take a dip daily to pay obeisance to the holy Ganga. As per legend, this is the exact spot where drops of nectar fell from the celestial pitcher (kumbha) when it was being carried away for the Gods after the churning of the ocean. This is also the point where the Ganga River enters the plains, and is hence held in reverence by all Hindus. Since Kankhal is home to several ancient temples and ashrams, there are many havelis and estates that attract tourists from all over the world. Thus, huge amounts of wastes are generated, which ultimately drain into the river through urban run-offs, rainfall, and mismanaged disposal of solid waste. Singhdwar harbours many hotels, markets and residents too; hence, there is direct or indirect discharge of domestic and hotel waste into the river.
In spite of the Ganga River in Haridwar being cleaner as compared to the other two locations, it must be noted that hydrodynamic conditions, turbulence, domestic and industrial waste discharges can influence the microplastics distribution pattern. Thus, the flow of water in Haridwar and the resulting turbulence may partly be responsible for a lot of microplastic pollution being swept away, as compared to downstream cities.
The number of microplastics detected in surface water samples of Ganga River in Kanpur was 2.16 MPs/m3. Although the discharge of sewage water into the Ganga via the Sisamau nullah has completely stopped since December 2019, large amounts of microplastics were detected at this point. At another point, upstream of Dohri Ghat, where more than 20 sewage treatment plants are now operational, there were large amounts of microplastics found too. Both these points showed approximately the same number of MPs (2.67 MPs/m3). Wastewater from the sewage treatment plants and the presence of famous temples and many tourist attractions are possibly the reasons for the heavy plastics pollution at this point. The presence of textile industries and tanneries in Kanpur can also be the reason behind large amounts of microplastics in the Ganga River here. At other points, microplastics ranged between 1.56 and 2.11 MPs/m3.
The number of microplastics detected in the surface water of Ganga River in Varanasi was 2.42 MPs/m3. Within Varanasi, Assi Ghat—the most popular bathing ghat in the pilgrim town, showed the highest number of microplastics at 2.82 MPs/m3 followed by Kedareshwar Ghat (2.60 MPs/m3), Dasaswamedha Ghat (2.56 MPs/m3), and Sheetala Ghat (2.33 MPs/m3). The lowest concentration of microplastics was near the Assi River, which is possibly due to the heavy flow in the river, which causes increased dispersion of microplastics at this point.
The observed particles were sorted into fibres, fragments, films, and beads. Fragments were the predominant shape in all locations, followed by film and fibre. At Kanpur, owing to a flourishing textile industry in the city, fibres were more abundant than films. At Varanasi, the ghats being popular for bathing, microbeads—which are found in scrubs, detergents, soaps and cosmetics—abounded. There were hardly any microbeads found in the waters off Kanpur. Surprisingly, no beads were found in Haridwar either, possibly because of the heavy flow of the river there.
Black and brown-coloured particles were found in more numbers followed by coloured particles in all three locations. Dominance of black-coloured particles (mainly fragments) are due to the abrasion of tyres on road surfaces, since the black fragments were mainly composed of styrene-isoprene rubber, and polyacetal. This was in contrast with other studies worldwide showing predominance of coloured microplastics, which come from packaging and clothing materials wherein dyes and pigments are added.
Incidentally, as per studies done, microplastic concentration in the Ganges waters is much higher than in other parts of the globe, notwithstanding the higher per capita consumption of plastics in Europe, North and South America, as compared to India.
Hazards from Microplastics Pollution of Rivers
A single personal care product with microbeads can result in the release of around 5000–95,000 microbeads. Thus, billions of microbeads are released into rivers and oceans globally. Being very tiny, microbeads often cannot get trapped through normal water filtration systems. Once they enter the water system, they absorb toxic chemicals such as petrol, engine oil, pesticides, and industrial sewage. Phytoplanktons and fish ingest these and often die. Otherwise, they may suffer from gut blockage and intestinal damage.
Microfibres are made up of plastic polymers like polyesters, nylon, rayon, polyethylene terephthalate (PET), polypropylene (PP), acrylic or spandex and have diameters lesser than 5 mm. Synthetic microfibres are made up of non-biodegradable polymers including nylon, polyester (PE), rayon, PET, polypropylene (PP), acrylic or spandex having a diameter less than 5 mm. Microfibres are generally released into rivers and waterbodies during domestic and industrial washing. Fragmentation of large plastic products, such as fishing nets can also release tonnes of fibres. Once they end up in rivers and water-bodies, fibres absorb toxic chemicals, heavy metals and oils and can become lethal, since they can bind with hydrocarbons, biphenyls and ethers easily. In aquatic environments, these may even release
carcinogenic toxins. When ingested by plankton, fish and aquatic creatures, they enter the food chain. Fish, oysters, and prawns exposed to microbeads and microfibres can cause respiratory problems, and damage to liver and kidneys when eaten by humans.
Ingestion of plastics by aquatic species may be through the following three routes:
Primary ingestion
Primary ingestion occurs when an animal directly eats plastic litter by choice and represents the best-studied type of plastic litter ingestion. This may be due to mistaking the item for something edible from visual and/or tactile cues. Plastic litter ingestion may also be due to curiosity, especially in young or juvenile animals, which are more likely than adults to eat litter across many species or an act of desperation from hunger.
Secondary ingestion
Species that prey on those that are known to ingest plastic litter are likely to secondarily ingest litter; for example, raptors that prey on ducks in areas where duck shooting occurs commonly secondarily ingest lead shot.
Incidental ingestion
This occurs when an animal ingests plastic litter from the environment while targeting its natural food. Animals that forage by suction or swallowing water/sediment and filtering food are more likely to accidentally/incidentally ingest litter than those that focus their energy on selectively targeting the prey and foraging visually. Incidental ingestion may also occur where visibility is poor, such as in turbid water. For instance, some of the highest known loads of ingested plastic litter come from the sperm whale, a species that commonly forages by suction in the deep ocean where light does not penetrate, precluding visual foraging.
The CMS/UNEP study analysed the waters of the Ganga River at ten different points and assessed the risks from microplastics pollution on 19 different aquatic species, on account of ingestion and entanglement in plastics debris. Going by the findings, the gharial (riverine crocodile) and the Gangetic river dolphin were found to be at high risk from entanglement in fishing debris such as torn and discarded fishing nets, with such encounters proving potentially lethal. Ingestion of microplastics was found to be moderately risky for the Gangetic river dolphin, while proving to be less risky for the gharial. Thus, one can conclude that cetaceans and reptiles are at risk from microplastics, with several avian species at varying risk, depending on their exposure to debris and foraging habits.
Antidote to Microplastics Pollution
As of now, wastewater treatment plants are the only barriers to check microplastics from flowing into riverine waters, and thence, into the sea. Although not all microplastics can be removed through water treatment, studies show that primary and secondary treatment of wastewater can remove a large part of microplastics, and prevent them from polluting riverine waters. Studies show that 78–98 per cent of the microplastics get removed in the primary stage, while an additional 7–20 per cent can be removed at the secondary stage. Since tertiary treatment varies from plant to plant, one cannot determine the exact amount that is removed. However, every wastewater treatment removes a large amount of microplastics as sludge, although there is no waste treatment plant that can yet remove microplastics completely. It is, hence, imperative that there are ample water treatment plants to treat domestic and industrial sewage along the course of the Ganges. For complete removal of MPs in the near future, further research into new and improved methods of treatment will be essential.
Bathing ghats are a major source of plastic microbeads that are used in cosmetics and toiletry. Hence, bathing needs to be regulated in Varanasi, Haridwar, and other pilgrim centres. In many countries, a ban has been imposed on the use of microbeads in cosmetics and toiletry. This could be implemented in India too.
Dr Rina Mukherji is an independent journalist with more than 27 years of experience. She holds a doctorate in African Studies and has several media and academic awards to her credit.
This article and more from TerraGreen can be viewed here: https://terragreen.teriin.org/