Sources of microplastic
Microplastics differ in their size, specific density, chemical composition and shape [126]. They are present in day to day products such as cosmetics, paints, etc. (primary microplastics), or from the degradation of larger macroplastic debris by environmental factors (secondary microplastics) [111, 127] (Fig.4).
Primary microplastics
Primary microplastics are manufactured for various domestic and industrial purposes. They are used in facial cleansers, hair coloring items, insect repellents, toothpaste, abrasives, synthetic clothing, cleaning products etc [4, 127, 128-130]. These products are described as open use products as they are washed off and drains in the environment [129]. Chang, on the other hand, identified polyethylene beads used in facial cleansers varying from 60 to 800 μm and reported that roughly 5000 g of microplastics were drained annually in the waste stream.
Secondary microplastics
Secondary microplastics are formed when larger plastic debris at sea and land subjected to physical, chemical and biological processes decreases the structural stability of macroplastic debris, resulting in fragmentation [4]. The fragmentation process is more active on beaches due to the presence of high UV light (photo-degradation), physical wave abrasion, supply of oxygen [4, 131] and turbulence [132]. If these fragments reach surface waters or deep habitats, colder temperatures and decreased UV light makes the breakdown process to slow down [131]. The degradation persists until the particles become smaller and microplastic in scale [4, 133]. It has been reported that about 245 tonnes of microplastics are generated per year which ends up in water sources where they are absorbed and ingested by marine organisms [134, 135].
Waste water treatment plants (WWTPs)
Significant amounts of microplastics are found in discharges from waste water treatment plants (WWTPs), and most are released out into the rivers. The predominant purpose for WWTPs is to handle waste water; however, they add a bulk amount of microplastics into the marine environment due to their improper disposal [136, 137]. In Tertiary treatment, full recovery was reached, which was not expected when secondary treatment has been used. Although most WWTPs use only secondary treatment, tertiary treatment performs better. Even then, tertiary treatment eliminates only 99.2% of microplastics.
Publication data
The original research articles in marine pollution bulletin (40.74%), science of the total environment (18.52%), environmental science and pollution research (7.41%), chemosphere (5.56%), environmental pollution (5.56%), environmental geochemistry and health (3.70%), environmental monitoring and assessment (3.7%), archives of environmental contamination and toxicology, journal of cleaner production, environmental forensics, regional studies in marine science, journal of environmental science and health C, journal of environmental chemical engineering, water, air, & soil pollution, and marine biological association of India (1.85% respectively) category of Web of Science are preferred to explore microplastic and plastic research (Table 1).
Spatial distribution of microplastic in India
In this part, we have selected 44 papers of beach sand (38.64%), Biota (27%), sediments (11%), island (7%), sea salt (4%), riverine (4%), lake (4%), and seawater (2%) of concentration, size, and spatial distribution of microplastic in the entire environment (Fig. 5 and Table 2).
Microplastic (MPs) in beaches, shores, and coastlines
The concentration of plastic debris average of 204 items/kg and about 100% of total plastic debris is 0.5 to 1 mm in size found in Silver Beach, Southern India [70]. The polymer types were polyvinyl chloride, polyethylene, and nylon identified using ATR-FTIR. The macro-meso-microplastic concentration of 3.77 items/m2, 9.5 items/m2, and 54 items/ m2 respectively, and their distribution of macro-meso-microplastics were 54.98%, 60%, and 41.17% and > 2.5 cm, 5-2.5 cm, 5 mm in size found in the beaches of Tuticorin Southern India [71]. The polymer types were PE, PP, PET, NY, PS, and PVC identified using ATR-FTIR. [73] reported that the concentration of plastic debris average of 2275 items and about 100% of total plastic debris is 5.5 to 25 mm in size found in Marina beach in Chennai, India. The polymer types were LDPE, PE, PP, PA, and PC identified using ATR-FTIR; TGA-DSC and SEM. The microplastic concentration of 414.35 items/kg and about 100% of microplastic ranges from 100-1000µm in size found in the sediments of the Andaman beaches, India [74]. The polymer types were PP, melamine, polybutadiene, polysulfide, poly (dimer acid-co-alkyl polyamine), PVC, NY-6, acrylonitrile butadiene styrene, poly (butadiene-acrylonitrileacrylic acid), polyvinyl formal, poly (perfluoroethylene oxide), polyvinyl benzoate, and epoxy epichlorhydrin identified using Raman spectral. The plastic debris concentration average of 22.4 kg dry weight/km2 and their distribution of 40.6% in the Northeast Arabian coast, India [75]. The polymer types were plastic bags, styrofoam cups, beverage bottles, bottle caps, plastic rope, net pieces, food wrappers were identified. The presence of plastic debris concentration of 2g/Kg in the seawater of South Juhu creek, Mumbai, India [69]. The concentration of microplastic concentration of 385 items/kg and their distribution of microplastics were 100% and 0.5 to 3 mm in size found in the sediments in coastal areas of Tamil Nadu [78]. The polymer types were PE, PP, NY, PES, and PS identified using FTIR-ATR, and SEM-EDAX.
[79] reported that concentration of microplastic concentration of 220 MPs/kg, 181 MPs/kg, 45 MPs/kg (Girgaon Mumbai, Tuticorin beach, and Dhanushkodi beach respectively), and their distribution of microplastics were 100% and > 1 mm in size found in the Arabian sea coast, Bay of Bengal coast, India. The polymer types were PET, PE, PVC, PP, PS, polyester, and polyamides identified using SEM-EDS, Fluorescence microscopy, and FTIR. [80] reported that concentration of plastic concentration of 0.55 kg/100m2 and their distribution of 73.8% in the beaches in Kerala Coast, India. The polymer type was plastic identified. [81] reported that concentration of microplastic concentration of 191 items/kg, and their distribution of microplastic is 70% and 5-1 mm in size found in the Nattika Beach, Kerala Coast, India. The polymer types were PE, PE + PP, PP, PS, and PCU identified using FTIR and SEM. [82] reported that concentration of plastic debris concentration of 8.96 kg/m and their distribution of 56.42% in the beach litter along Chennai, East Coast of India. The food wrappers, cups, bottle and caps, thermocol/styrofoam, and food wrappers identified. [83] reported that concentration of microplastic concentration of 72.03 MPs/100g and their distribution of 56.32% and 300μm-1mm in size found in the beaches of Puducherry, India. The polymer types were polyurethane, HDPE, polypropylene, polystyrene, and LDPE identified using Raman spectroscopy. [85] reported that microplastic concentration of 403 pieces and their distribution of 60.8 % and >1.01-200mm in size found in the Rameswaram beach, GoM, Southeast coast of India. The polymer types were polyethylene, polystyrene, nylon, and polyvinyl chloride identified using FTIR spectroscopy. [86] reported that plastic debris concentration of 505 pieces in the Nallathanni Island, SE of India. The polymer types were polystyrene, polyethylene, polycarbonate, polyvinyl chloride, and nylon identified using FTIR spectroscopy.
[88] reported that concentration of plastic debris concentration of 3.24 kg and their distribution of 44.89% in the Marina beach, Chennai, India. [91] reported that plastic debris concentration of 7.49 g and their distribution of 55.33% and 1-5 mm in size found in the beaches in Mumbai, India. The polymer type was plastic identified. [92] reported that concentration of plastic debris concentration of 3.24 g m-2 and their distribution of 80% and 5-100 mm in size found in the beaches in Mumbai, India. The polymer type was plastic identified. [60] examined that presence of microplastic concentrations average of 134.29 items/kg in the sediments, and 19.87 items/L in water, and their distribution of microplastics were 44%, and 58% in sediments, and water respectively. The particle size range of 1-5mm, and 500µm-1mm (in sediment, and water respectively) along the coast of the Tuticorin, Gulf of Mannar (GoM), India. The polymer types were PE, PP, PP-PE, PA, PET, PEST, PVC, PS, RA, and PVA identified using FTIR-ATR, SEM, and EDAX. [65] examined the presence of microplastic concentrations average of 12.75 items/kg in sediments, and 21.60 items/L in seawater, and their distribution of microplastic is 100, and 100 % respectively. The particle size ranges from 1-3 mm, and 0.5-1 mm respectively in the Roche Park, Coast of Tuticorin, Gulf of Mannar, Southeastern of India. The polymer types were PE, PP (Magallana bilineata), PE, PP, polyester, polyamide & paint in sediments, and PE, PP in seawater identified using FTIR-ATR analysis. In quantities of plastic debris is highest amount of 8.96 kg/m in marine beach to prove that shoreline and recreational activities are the primary cause of beach debris litter along Chennai, India [82].
[96] reported that microplastic concentration of 277.90 items/kg and their distribution of 49% and 0.01 - 3 mm in size found in the Beaches of Puducherry, India. The three polymer types were poly (ethylene; propylene; styrene) identified using Celestron Digital Microscope. [97] examined that presence of microplastic concentrations of 0.93/m3, and 45.17 /kg (water, and sediments respectively). The particle size range of 35.29 to 5010 μm, and 46.72 to 5024 μm (in water, and sediments respectively) in the Port Blair Bay, Andaman Islands, India. The polymer types were ionomer surlyn, poly etherimide, acrylic (Acryl Fiber), polyphenylene sulfide, ethylene vinyl alcohol, acrylonitrile, nylon, ethylene-vinyl acetate, polyisoprene, polyurethane, PVC identified using FTIR-ATR. [98] reported that plastic debris concentration of 1029 items/m2 and their distribution of 96% and > 1 mm in size found in the Vavvaru Island of the Maldives, Indian Ocean. The polymer types were polyethylene, polypropylene and polystyrene, but polyurethane, polyamide, polyvinyl alcohol and polyvinyl chloride identified using ATR-FTIR spectroscopy.
[99] examined the presence of microplastic concentrations of 288 pieces/m3, 96 pieces/kg, 84.45 pieces/kg in water, sediments, and soil respectively), and their distribution of microplastic is 86.51%. The particle size range of 1-5 mm and 0.3-1 mm in the Netravathi river, India. The polymer types PE, PET, PP, and PVC identified using FTIR-ATR. Due to its widespread usage as packaging materials, higher polyethylene abundance is the primarily used plastic raw material in Indian industries [138]. The compared with other rivers, In Portugal's Antua River, microplastics abundance ranged from 13.5 to 52.7 mg/kg in March, and 2.6 to 71.4 mg/kg in October [139], higher than Haihe River [140] and marginally lower than Pearl River [141, 142]. [100] examined that MPs concentration ranges from 0.68 to 148.31 ng/g and 11-64 ng/g items/kg and their distribution of 70% and 5 to 10 mm in size found in the riverine sediments of Ganga, India. The polymer types were PET, PE, PP, and PS identified using FTIR. This degree of microplastic abundance was found to be smaller than other world rivers. Likewise, plastic debris concentration ranged from 228 to 3760 items/kg in the Rhine river [143], 178-544 items/kg in the Beijiang river [119], and 185-660 items/kg in the Thames river [32] which is less than previous.
The numerical fraction of microplastics in the Ganga was identified higher compared to the concentration of microplastic ranges from 0.60–160 items/kg in the Bloukrans river, South Africa [144]. This disparity in the concentration of meso and microplastics in these rivers is due to several factors including pollutant loading, hydrodynamic state and spatial location [145, 146]. Depending on these considerations, certain places were observed to have large concentrations of plastics relative to others. PET, PE, and PP were the most popular plastic forms in Ganga river sediments, while fibres (polyesters) and sheet or film were the most significant morphotypes. Compared to other morphotypes such as film and beads, microplastic waste highlighting fibers was recently emphasised [147].
[76] reported that microplastic concentration of 343 items 50 g−1 d.s. and their distribution of 100% and <5 mm in size found in the southernmost coast of India (Kanyakumari), India. The polymer types were fiber and fragment identified. [77] examined that presence of microplastic concentrations of 40.7 particles/m2, 1.25 particles/m3, 22 particles in sediments, water, and fish respectively), and their distribution of microplastic is 96.10%. The particle size range of 0.3-0.6, 0.6-1.18, and 1.18-2.36 mm in the Kerala, Southwest coast of India. The polymer types PE; PP; PA; PS; PET; RY; PUR; alkyd; CE; ABS; PVC; PVFM sediments, PE; PP; alkyd; RY; PS; CE in water, and PE; CE; RY; PL; PP in fish identified using FTIR-ATR, FP-XRF. [87] reported that microplastic concentration of 496 items m-2 and their distribution of 91% and <5 mm in size found in the Vembanad Lake, Kerala, India. The polymer types were Polymers; Polypropylene; polyethylene, and polystyrene identified using Raman spectra. [89] reported that microplastic concentration of 5500 pellets found in the Goa coast, India. The polymer types were PE and PP identified using FTIR-ATR. [148] reported that microplastic concentration of 1200 pellets 2 to 5 mm in size found in the found in the Chennai coast, India. The polymer types were Polyethylene and Polypropylene identified using FTIR-ATR.
[93] examined the presence of microplastic in sea salt, and their distribution of microplastic is 60%. The particle size of 100 μm in the Tuticorin coastal salt pan stations, Gulf of Mannar, South India. The polymer types PE, PP, CL, and NY identified using μ-FT-IR and AFM. MPs were also recently reported from Arctic sea ice, fish, sea birds and sea salts in heavily polluted surface waters. Only a small range of global studies have been carried out on the quantity and distribution of MPs in marine salts [149-153]. [94] reported that microplastic concentration of 72 items/kg and their distribution of 100% and 100 to 500 µm in size found in the sea salt in the Salt of Tuticorin, Southeast Coast of India. The polymer types were polyethylene, polypropylene, polyester, and polyamide identified using SEM-EDAX. The study shows that people consume around 216 MPs/year particles through sea salt if the average individual has 5 g daily salt intake.
[95] investigated the MPs concentration of 103 particles kg-1 and their distribution of 80% and 2000 μm and 500 μm in size found in the sea salt in the Mumbai, Indian sea salts, Southeast Coast of India. The polymer types were polyesters, polystyrene, polyamide, polyethylene identified using μ-FTIR. Microplastic abundance in sea salts may be due to sea salt being a direct product of coastal water. The amount of MPs in the salt samples tested by this analysis was observed to be smaller than those in China and Spain's sea salts and well salt [154, 155]. Low-density MPs may also be transferred from surface soil to deeper soil levels horizontally and vertically through soil fractures as well as by earthworms, collembolan and other species [156-159]. It may also be affected by airborne pollution [155, 160, 161].
[101] examined the presence of microplastic concentrations of 309 items/kg, 28 items/km2, 5.9 items/L in sediments, and water respectively), and their distribution of microplastic is 80%. The particle size range of -1 to 0.3 mm, 0.3-2 mm in the Veeranam lake, Tamil Nadu, India. The polymer types such as nylon, polyethylene, polystyrene, polypropylene, and polyvinyl chloride identified using ATR-FTIR. [102] examined that presence of microplastic concentrations of 5.9 particles/L, 27 items/kg, in water, and sediments respectively), and their distribution of microplastic is 99%. The particle size range of 0.33-2 mm in water, 2 mm in sediments of the red hills lake, India. The polymer types were HDPE, LDPE, PP, and PS identified using ATR-FTIR, SEM. The causative factors of these microplastics are primarily attributed to the weathering phase degradation of plastic goods and even from fishing nets, as these are the significant contributors of microplastics in water and sediments [162-164]. A further probable route for microplastic is by dry deposition, by wind transport. The dust generated by, i.e., automotive emissions, tyres [165] from the soil, deposition and dispersion between the atmosphere, the environment and the marine domain may also promote the transportation of microplastic [166], although this requires detailed analysis [167].
Ecotoxicological effects of microplastics on biota
Microplastic particles were found in many aquatic biota, such as fishes (Anodontostoma chacunda, Arius arius (11), Carangoides armatus (20), Chirocentrus dorab (20), Coilia dussumieri (10), Cyanoglossus macrostomus (126), Decapterus russelli (10), Dussumieria acuta, Dussumieria elopsoides (10), Eleutheronoma tetradactylum (10), Epinephalus diacanthus (8), Epinephalus merra, Escualosa thoracata (10), Harpodon nehereus (20), Istiophorus platypterus (10), Katsuwonus pelamis (10), Leiognathus equulus (10), Leiognathus splendens (6), Megalaspis cordyla, Mugil cephalus, Nemipterus japonicas (20), Nemipterus randalli (38), Pentaprion longimanus (20), Piaractus brachypomus, Rastrelliger faughni (10), Rastrelliger kanagurta (168), Sardinella albella (20), Sardinella gibbosa (41), Sardinella longiceps (144), Saurida tumbil (13), Scomberomorous guttatus (10), Siganus javus (29), Sphyraena obtusata, Stolephorus indicus (148), Terapon puta (33), Thryssa dussumieri, and Thryssa mystax (12); Shrimp (Fenneropenaeus indice - 330), bivalve (Perna viridis & Meretrix meretrix - 50), mollusca (Donax cuneatus -225, Perna viridis (Linnaeus, 1758), oyster (Magallana bilineata), Annelida (Sternaspis scutata, Magelona cinta and Tellina sp), and zooplankton - copepods (100), chaetognaths (50), jellyfish (50), and shrimps (20), fish (72). Fourteen studies reported the intake of microplastics by aquatic species in India. From these researches, 1895 aquatic organisms were analysed and more than 95% of the species studied were found to be infected by microplastic particles (Table 3).
Microplastics (MPs) in vertebrates
Two primary mechanisms absorb microplastics into vertebrates: predators feed on food already infected with microplastics (through intake or external microplastic), or predators directly absorb microplastics from the water, and sediments. Microplastics in different forms were found in 1470 no. of fishes (52 species) in India (Table 3).
Microplastics were present in the gut and intestine of fishes namely as Dardanelle longiceps (123), Rastrelliger kanagurta (130), Dardanelle gibbosa (40), Carangoides armatus (20), Stolephorus indicus (127), Epinephalus diacanthus (8), Saurida tumbil (13), Terapon puta (13), Nemipterus randalli (38), Leiognathus splendens (6), Cyanoglossus macrostomus (106), and Thryssa mystax (12). The particle size range from > 1-5mm and 81.59% distributed in fishes of Kochi, south eastern Arabian Sea, India [57]. The polymer types were PE; PP; LDPE identified using Raman spectroscopy and FTIR. Average microplastic concentrations of 0.2002 items/g were found in gastrointestinal tracts of fishes, and 13.4 items/L in seawater and their distribution of microplastic is 34% and 64% (fish and seawater respectively) [61]. The particle size range of <500 μm, and 1-5mm (in guts, and seawater respectively) in the Tuticorin, Southeast coast of India. The polymer types were polyethylene, polyamide, polyester, polystyrene, polypropylene and acrylic in fishes, and polyethylene, polyester, polyamide, polystyrene, polypropylene, polydiene, PP-PE, and PLA in seawater identified using FTIR-ATR and SEM-EDAX. [58] examined the presence of microplastic concentrations average of 0.005 items/g in edible tissues, and 0.054 items/g in inedible tissues of fishes, and their distribution of microplastic is 11.6% and 88.4% (edible and inedible tissues respectively). The particle size ranges from 115-210 μm, and 136 to 4010 μm (edible and inedible tissues respectively) in the Kerala, India. The polymer types were PE, PP in edible tissues and PE, PP, EPDM, PS in inedible tissues of fishes identified using ATR- FTIR.
[62] reported the concentration of microplastic is 26.01 items/g in the gut of the alien fish of Piaractus brachypomus (123). The particle size of 0.5mm and their distribution of 99% in the Ramsar, Vembanad lake, South India. The polymer types were PBT, PP, PET, and NY 6 identified using ATR-FTIR and Raman spectroscopy. Microplastic concentration of 20 items/g in the gastrointestinal tract of fishes such as Coilia dussumieri (10), Decapterus russelli (10), Decapterus macarellus (20), Dussumieria elopsoides (10), Eleutheronoma tetradactylum (10), Escualosa thoracata (10), Nemipterus japonicas (20), Pentaprion longimanus (20), Rastrelliger faughni (10), Sardinella longiceps (20), Scomberomorous guttatus (10), Stolephorus indicus (20), and Terapon puta (20) [63]. The particle size ranges from 1.3µm - 9.3mm and their distribution of 8.95% in the Chennai and Nagapattinam, Southeast coast of the Bay of Bengal. The polymer types were PA, PE, and PET identified using FTIR & SEM.
About 80% distribution of microplastic found in the intestine of Rastrilleger kanagurta (20), and Epinephalus merra (20) [66]. The particle size ranges from 0.5 mm to 1 mm in the Tuticorin, South east coast of India. The polymer types were polyethylene & polypropylene identified using FTIR. [84] examined the microplastic concentrations of 46.6/m2 in gut of Rastrelliger kanagurta (17), Siganus javus (29), Arius arius (11), Leiognathus equulus (10), and Mugil cephalus (12) (Fishes), 9233mg/m2 in sediments, and their distribution of microplastic is 60.1% respectively. The particle size ranges from 1-2.5mm respectively in the beaches of SE coast of India. The polymer types were PE, PP, PS, and NY identified using FTIR-ATR analysis. Microplastic concentrations of 10.65 specimens in finfish & shellfish, and their distribution of microplastics were 45.83% in fishes such as Alepes djedaba (6), Cynoglossus lida (6), Saurida tumbil (9), Gerres filamentous (13), Nemipterus peronii (8), Upeneus vittatus (10), Carangoides malabaricus (4) (Adult), and Carangoides malabaricus (6) (Juveniles), and shellfish. The particle size range of 111.58 to 5094 μm in finfish & shellfish in the Port Blair Bay, Andaman Islands, India. [97] the polymer types were ionomer surlyn, poly etherimide, acrylic (Acryl Fiber), polyphenylene sulfide, ethylene vinyl alcohol, acrylonitrile, nylon, ethylene-vinyl acetate, polyisoprene, polyurethane, poly vinyl chlorid identified using FTIR-ATR.
In conditions of particles per organism, larger vertebrates have eaten higher concentrations of microplastics than fish. Highest microplastic abundance values were reported in India's southeast coast [97]. By examining microplastic abundance in fish from different studies in India, we found that microplastics abundance in Indian fish was of the same magnitude as in other countries. For particles per weight, microplastic was identified in Istiophorus platypterus showed in the Tuticorin, Southeast coast of India, which had an abundances of 0.0002 MP/g in gut, 1.10 MP/g in body, and 0.11 MP/ individual due to depth about >200m [94]. In terms of depth of locations, microplastic was concentration is 0.2 MP/g in gut, 0.008 MP/g in body, and 3.64 MP/ individual found to be Harpodon nehereus due to depth above 1-3 m. In conditions of particles per weight, microplastic was found to be Piaractus brachypomus showed in the Ramsar, Vembanad Lake, south India, which had 26 % MP intake in fish [62].
Microplastics (MPs) in invertebrates
In the ecological food web, microplastic toxicity has been observed to influence both the basal food web species and all kinds of species [114]. Indian invertebrate absorption of microplastic particles was studied in bivalves, shrimps, and other benthic species. At present, six studies have analyzed microplastic contamination in invertebrates in India and 508 organisms have been reported to be microplastic polluted (Table 3). Among these species, bivalves are of particular concern since their extensive filter-feeding practices expose them to plastics in the waters they visit [110, 168]. The confirmed rate of microplastic ingested by aquatic invertebrates was 58.58%. The microplastic abundance in aquatic invertebrates in India ranged 0.04 to 3.78 and from 0.39 to 7.05 items/g. [58] reported the presence of microplastic is 0.04 items/g (0.39 ± 0.6 items/shrimp) in the foregut and midgut of Fenneropenaeus indices (Shrimp - 330). The particle size range from 500 to 1000 µm and 30.9% distributed in Cochin, Kerala, India. The polymer types were poly (amide, ester, ethene, and propylene) identified using FTIR.
[59] reported the presence of microplastic is 3.78 g and 7.05 items/g (soft tissue and bivalve respectively) in the Perna viridis (90) and Meretrix meretrix (110). The particle size range of <100 μm in the Pondicherry, India. The polymer types were poly (amide, ester, ethene, and propylene) identified using Raman spectrum & Fluorescence microscope. [60] examined that presence of microplastic concentrations average of 0.95 items/g in clams (Donax cuneatus - 225), and their distribution of microplastics were 41% Donax cuneatus. The particle size range of 100-250µm in clams in the Tuticorin coast of Gulf of Mannar (GoM), India. The polymer types were PE, PP, PP-PE, PA, PET, PEST, PVC, PS, RA, and PVA identified using FTIR-ATR, SEM, and EDAX. [64] examined that presence of microplastic concentration is 0.9/g in the tissue of Perna viridis (Linnaeus, 1758) (5). The particle size ranges from 5-30 μm and their distribution of 87% in the Chennai, Southeast coast of India. The polymer type was PS identified using DXR Raman spectroscopic. [65] examined that presence of microplastic concentrations average of 0.81/g in tissue of Magallana bilineata (oyster) (180), and their distribution of microplastic is 96%. The particle size ranges from 0.25 to 0.5 mm in the Roche Park, Tuticorin coast, GoM, SE India. The polymer types were PE; PP (Magallana bilineata) identified using FTIR-ATR analysis. [67] examined that distribution of microplastic 67% in the gut of Sternaspis scutata, Tellina sp, and Magelona cinta. The particle size range of 20 µm in the Kochi, Southeastern Arabian Sea. The polymer types were polystyrene identified using DXR Raman microscope.
[97] analysed the concentration of microplastic in 10.65 specimens, 0.12 pieces (finfish & shellfish and zooplankton) and their distribution is 45.83 percent, 90% in finfish & shellfish, zooplankton respectively. The particle size spectrum in Port Blair Bay, Andaman Islands, is 111.58 to 5094 μm, 21.57 to 2225 μm (in finfish & shellfish, and zooplankton, respectively). Polymer forms were ionomer surlyn, polyetherimide, acrylic (Acryl Fiber), polyphenylene sulphide, ethylene vinyl alcohol, acrylonitrile, nylon, ethylene-vinyl acetate, polyisoprene, polyurethane, FTIR-ATR polyvinyl chloride. In term of particles per individual, the highest concentration of microplastics was noticed in Magallana bilineata (oyster) collected in the Roche Park, Tuticorin coast, GoM, Southeastern India which has an abundance no. of MPs 29.19 items/ individual and no. of 1.73 MPs items/g [65]. In similar that, the largest concentration of microplastics was found in oysters (Crassostrea gigas) obtained in Sangou Bay, Yellow Sea, with a concentration of 43-164 ind.-1. By contrasting the abundance of microplastic in commercial invertebrates in China and other countries across the world, Chinese microplastic emission levels were found to be generally higher than in other countries.
Microplastics (MPs) size in different aquatic environments and biota
A main element affecting the ingestion of microplastic particles is their small size, as many low-trophic species have little potential to turn plastic from food and would feed upon it which is reasonable in size [119, 169]. In general, size was also strongly linked to microplastics toxicity [170]. In the 53 reviewed papers, 35 researches recorded the size spectrum (Table 3). The highest value varied from 9.3 mm to 5mm, and the minimum values varied from 0.005 to 1mm. Twelve biota experiments determined size groups. Most experiments have found microplastics in the size class of less than 1 mm (83 percent of biota articles). However, larger microplastics overshadowed certain fish research. For example, larger microplastics were identified in fish (0.0013-9.3 mm) from Chennai and Nagapattinam, Southeast Bay of Bengal [63], fish captured from the Kochi, south eastern Arabian Sea, India (particle size range from > 1-5mm [57], fish (inedible tissues) captured from the Kerala, India (Size: 0.136 to 4.010mm [58], fish (gut) captured from the beaches of southeast coast of India (Size: 1-2.5mm [84], Shrimp captured from the Cochin, Kerala, India (Size: 0.5-1 mm; Daniel et al., 2020), the plastic debris size ranges from 0.5-25 mm in the beach sediments. In marine Chennai beach has been size in 5.5-25 mm in beach sediments [73]. The irregular plastic particles are produced mainly from dampening household plastic materials by urban drainage and partly by sea. Previous reports indicate a higher distribution of fragments and fibres than other sources in coastal sediments [171-173]. Polymer types such as polyethylene, polypropylene, and polystyrene float on seawater and fly long stretches, having been located far from their primary origins [174].
Cleaner sea
National Marine Litter Policy in India
India releases 600,000 tonnes of plastic waste annually into the oceans. We need to develop the right clean-up technology to overcome the marine plastic pollution. In order to regulate identify and monitor the source of plastic litter along the India’s coastal line the Union Ministry of Earth Sciences took an initiative to clean up the oceans by adopting National Marine Litter Policy along with UN Environment’s global ‘Clean Seas Campaign’ on 2018. This policy is about how do we reuse and recycle plastic for cleaner sea. National marine litter Policy aims in (i) identifying the path of plastics from source to sink and promoting Reduce, Reuse and Recycle (3R’s) concept to create awareness (ii) enumerating the plastic litter in marine sediments, water and biota along the Indian coast (iii) to build a monitoring, management and mitigation procedures to overcome the impact of Microplastics to clean up oceans.
Research gap
Main criteria to tackle research gaps pertaining to microplastics in the marine environment.
- Present a optimal and standardised size description of a microplastic, with additional size specifications for nano- and mesoplastics
- Improve and adopt systematic, high-throughput microplastic sampling methodologies to effectively correlate the outcomes from various research areas
- Establish effective methods to identify tiny microplastics and nanoplastics in water columns and sediments
- Broaden understanding of the nature and behaviour of microplastics in the water column, together with the consequences of fragmentation and bio-fouling.
- Adapt methods to assess microplastic absorption by biota in the food web and extend usage of sentinel organisms (e.g., Fulmars) to detect microplastic abundance in the marine environment.
- Identify the impact of ingested microplastics (leached plastic additives, waterborne pollutants) on marine biota and recognize its transition within the food chain.
- Determine the microplastic wastes emitted from waste water treatment plants (WWTPs) that drains into the rivers.