Current State of Microplastics Research …
29
1 Introduction
It has been increasingly difficult for the present-day generation to imagine a world
without plastics. Plastic materials are durable and non-biodegradable and these properties make it more popular to the mankind and at the same time, a villain to the
ecosystem. The longer residence time of plastic materials in the natural environment
due to these properties poses a serious threat to the ecology [131, 134]. As time
passes, various factors, either biotic or abiotic, begin to degrade these materials to
smaller particles [2] and the extent of degradation depends on their physicochemical
properties [22]. Plastic is a common word applied to a group of polymers out of which
significant classes are polyethylene, polystyrene, polyvinyl chloride, polyethylene
terephthalate, polyurethane and polypropylene [63]. In recent decades, the generation of plastic waste has escalated at a shocking rate globally. Out of the 275 million
metric tons of plastic produced in 192 coastal countries in 2010, approximately 4.8–
12.7 million metric tonnes have reached the ocean [50]. The authors emphasized
the importance of proper waste management systems and stressed on the serious
consequences if the present scenario continues.
In modern times, environmental scientists are deeply concerned about ‘microplastics’ (Mps). They are small materials of plastic with a diameter <5 mm. Depending on
their mode of formation, they are classified as primary and secondary microplastics
[35, 69]. Primary microplastics are tiny plastics particles, produced for a particular
function and used as such, that are released into the environment [15, 35]. One of the
sources of these particles is facial cleansers, which contain polyethylene and they
cannot be trapped by wastewater treatment plants resulting in them ending up into the
oceans [33]. Some other sources of primary microplastics are manufactured pellets
used in plastic production or the feedstock, industrial abrasives for sandblasting,
plastic powders used in moulding, micro-beads used in the formulation of cosmetics
[35, 78, 142]. Smaller plastic materials resulting from the degradation of large-sized
plastics by the action of winds, UV radiation, currents, and microbes are secondary
microplastics [35, 69]. Microplastics can be categorized, based on their morphology,
into films, fragments, fibres, foams, and pellets [76, 64, 99]. In the past decade, the
presence of microplastics have been documented from different environments: estuarine [97], riverine [116], lake [72], beach [42], polar [125], mangroves [26], road
dust [43], soils [136], and even the atmosphere [141].
Due to its size, the harmful impacts of microplastics are much more significant than
that of large-size plastic waste. Several negative effects on biota due to microplastics
were reported including inhibited photosynthesis [13], weight-loss due to starvation [11], reduced filtration [133], impact on feeding and digestion [20, 35], and
even mortality [71]. The ingestion of these particles mistaken as food by the aquatic
organisms at the lower levels of food chain and their subsequent transfer through the
food chain is a serious ecological issue [135]. As microplastics enter the food chain,
the health of humans [124] and predators who feed on these organisms is under threat
[41]. This is supported by the fact that microplastics have been isolated from sea birds
[18], benthic invertebrates [81], fish guts [60], harbour seals—a marine mammal [95],
29
1 Introduction
It has been increasingly difficult for the present-day generation to imagine a world
without plastics. Plastic materials are durable and non-biodegradable and these properties make it more popular to the mankind and at the same time, a villain to the
ecosystem. The longer residence time of plastic materials in the natural environment
due to these properties poses a serious threat to the ecology [131, 134]. As time
passes, various factors, either biotic or abiotic, begin to degrade these materials to
smaller particles [2] and the extent of degradation depends on their physicochemical
properties [22]. Plastic is a common word applied to a group of polymers out of which
significant classes are polyethylene, polystyrene, polyvinyl chloride, polyethylene
terephthalate, polyurethane and polypropylene [63]. In recent decades, the generation of plastic waste has escalated at a shocking rate globally. Out of the 275 million
metric tons of plastic produced in 192 coastal countries in 2010, approximately 4.8–
12.7 million metric tonnes have reached the ocean [50]. The authors emphasized
the importance of proper waste management systems and stressed on the serious
consequences if the present scenario continues.
In modern times, environmental scientists are deeply concerned about ‘microplastics’ (Mps). They are small materials of plastic with a diameter <5 mm. Depending on
their mode of formation, they are classified as primary and secondary microplastics
[35, 69]. Primary microplastics are tiny plastics particles, produced for a particular
function and used as such, that are released into the environment [15, 35]. One of the
sources of these particles is facial cleansers, which contain polyethylene and they
cannot be trapped by wastewater treatment plants resulting in them ending up into the
oceans [33]. Some other sources of primary microplastics are manufactured pellets
used in plastic production or the feedstock, industrial abrasives for sandblasting,
plastic powders used in moulding, micro-beads used in the formulation of cosmetics
[35, 78, 142]. Smaller plastic materials resulting from the degradation of large-sized
plastics by the action of winds, UV radiation, currents, and microbes are secondary
microplastics [35, 69]. Microplastics can be categorized, based on their morphology,
into films, fragments, fibres, foams, and pellets [76, 64, 99]. In the past decade, the
presence of microplastics have been documented from different environments: estuarine [97], riverine [116], lake [72], beach [42], polar [125], mangroves [26], road
dust [43], soils [136], and even the atmosphere [141].
Due to its size, the harmful impacts of microplastics are much more significant than
that of large-size plastic waste. Several negative effects on biota due to microplastics
were reported including inhibited photosynthesis [13], weight-loss due to starvation [11], reduced filtration [133], impact on feeding and digestion [20, 35], and
even mortality [71]. The ingestion of these particles mistaken as food by the aquatic
organisms at the lower levels of food chain and their subsequent transfer through the
food chain is a serious ecological issue [135]. As microplastics enter the food chain,
the health of humans [124] and predators who feed on these organisms is under threat
[41]. This is supported by the fact that microplastics have been isolated from sea birds
[18], benthic invertebrates [81], fish guts [60], harbour seals—a marine mammal [95],