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Abstract
A man
made ecosysyem – the plastosphere harbours living organisms thriving on
microplastics, now ubiquitous in aquatic environment. According to an
estimate, 51 trillion microplastics are floating on the surface of oceans. A
small piece of microplastic measuring 5mm can host thousands of different
microbial species. A plastosphere thus can be defined as “a microbial
ecosystem that develops on the surface of plastic debris particularly
microplastics in the aquatic environment”. It was first described by a team
of marine scientists (Zettler et al., 2013) while working on the
micro-organisms of Atlantic Ocean.
Plastic
was discovered in 1907 by Leo Backeland using formaldehyde and phenol. Since
then its use by human society has exploded multifold. Between 1964- 2014, its
applications increased twenty fold. Now, synthetic and semi synthetic
compounds are used to make a variety of plastics viz. polyethylene (PE), polyethylene
tetraphthalate (PET), polystyrene (PS), polypropylene (PP) and poly vinyl
chloride (PVC) (Auta and Emenike, 2017; Lu et al., 2021). In addition,
more than 10,000 chemicals are employed in plastic manufacturing. About 2000
of these substances are likely to affect the environment and human health (
Wiesinger et al., 2021). Recent estimates claim that approximately 1.1
billion tons of plastic will be dumped in the natural environment by 2050.
Richard
Thompson, a marine biologist coined the term microplastics (Mps) (Thompson et
al., 2004). Fragmentation of plastic produces primary microplastics (MPs)
which are less than 5mm in length. These particles are further classified as
microfibers, microbeads, plastic litter and plastic pellets. Primary
microplastics are further degraded through physical, chemical, biological,
and photo -degradation processes into secondary microplastics. Present global
load of MPs ranges from 93,000 to 236,000 metric tons (Ioakeimidis et al.,
2016). MPs are not the only end products of plastics but are further degraded
into nanoplastics (NPs). By definition, NPs measure less than 100 nm in size
(Dawson et al., 2018). They are ubiquitous in air, water, soil
and food and consequently, affect human health adversely (Lai et al.,
2022).
Plastics
contribute 80-85% of marine litter. Approximately, 5 to 13 million tons of
plastics, on an average, enter the oceans per year (Auta et al.,
2017). Around 229,000 tons of plastics are dumped every year into the
Mediterranean Sea alone (Macias et al., 2019). The highest
concentration of floating debris has been reported in this sea. Wang et al.
(2020) documented the highest concentration of MPs in the West Pacific Ocean.
MPs in the Indian Ocean including beaches, sub-tidal sediment, sediment of the
ocean floor and surface waters have been reported by Thiemann et al.
(2023). Finally, they settle down in the benthos and affect the marine
organisms.
In
atmosphere, MPs and NPs can travel long distance creating a never ending loop
of plastic transport (Allen et al., 2022). Air borne MPs and NPs have
been detected worldwide, especially in the northern hemisphere including
France, Iran, China, Japan, Vietnam, Nepal, USA, Saudi Arabia, South Korea,
Greece, Roamania, Pakistan and India (Ajith et al., 2020). Sources of
MPs/NPs in air include indoor air pollution, wearing of tyres and atmospheric
fallout (Dris et al., 2017).
Pollution
of agricultural soil by MPs/NPs loaded agrochemicals has also been reported
(Moeck et al., 2022). It has been argued that partition of MPs/NPs in
different soil matrices can modify their bioavailability in plants. Further,
apoplastic and synplastic pathways can facilitate their absorption by roots.
Bioaccumulation of MPs/NPs may induce oxidative stress and gene expression
changes that will determine the plant growth, biomass production and
synthesis of secondary metabolites (Maity et al., 2022).
Prevalence
of MPs/NPs in fresh water ecosystems has rarely been studied. According to
Wagner et al. (2014), 80% of total plastic debris in the marine
systems are derived from terrestrial sources that are transported by
rivers. Major rivers of India viz., Ganges, Brahamputra and Meghna
discharge 1-3 billion tons of MPs in the Bay of Bengal every day (Napper et
al., 2021). The presence of MPs in ground water has also been reported (
Selvan et al., 2020a). Ubiquity of MPs/NPs in different
eco-compartments leads to their presence in food chain/food web. Microalgae,
the first trophic level in food chain are known to adhere to NPs, wherein
they inhibit growth, reduce chlorophyll content, decrease photosynthesis and
promote the formation of heteroaggregates. Zooplanktons, the second level of
food chain are also affected by MPs/NPs. MPs/NPs are absorbed, transferred
and biomagnified through food chain amongst rotifers, polychaetes,
crustaceans, mollusks, echonderms and fish (Prata et al. 2017).
Finally, MPs/NPs can reach human body and manifest into toxicity causing
health hazards (Zhu et al., 2024). Food sources like vegetables, fish,
sea food, table salt, sugar, honey, milk and even beer are known to be
contaminated with MPs/NPs (Vitali et al., 2022). Food packed/stored in
plastic ware constitute another source of exposure to MPs/NPs in humans
(Yadav et al., 2022). Many drugs and liquid pharmaceuticals are
packed, stored and transported in plasticwares to consumers. NPs can reach
skin, lungs, liver, kidney, heart and even immune system. Relationship
between MPs/NPs and tumorogenesis has also been established. NPs may contain
PAH that can cause DNA damage leading to carcinogenesis (Surya et al.,
2024).
Serious
attempts have been made in the recent past to address these problems at local
and global platforms. An International Intergovernmental Negotiating
Committee (INC, 2022) was set up by UN Environment Assembly (UNEA, 5.2).
During Basel Convention (1989), 187 countries had committed to solve the
plastic crisis. Ongoing researches on plastics and its chemical additives are
covered by Stockholm Convention on Persistent Organic Pollutants (2001) and Rotterdam
Convention on Hazardous Chemicals (1998). Environment Protection Agency
(USA) has formulated a strategy,” National Strategy to prevent Plastic
Pollution: part 3 of a series on building a Circular Economy for all
that offers an ambititious approach to recover plastics from other materials
and prevent plastic pollution. EU policy on plastics aim to protect the
environment and human health by reducing marine litter, green house gas
emissions and dependence on fossil fuels. Ministry of Environment, Forests
and Climate Change (MOEFCC) has enacted Plastic Management Rules, 2016 and
Plastic Management Amendment Rules, 2022. Central Pollution Control Boards
and State Pollution Control Boards enforce these rules and ensure the
registration of plastic brand owners and fulfillment of environment
protection rules.
Plastosphere
is not a natural eco-compartment but has evolved due to various anthropogenic
activities, mainly focused on micro and nanoplastics. Nonetheless, their
production and use in different sectors by the society shows no serious
concern to combat the problem. United Nations Environment Program in 2023
celebrated World Environment day with a slogan, “Beat Plastic Pollution”.
In 2025 also, UNEP celebrated World Environment Day with a a slogan, “Combat
Plastic Pollution”, with South Korea as the host country. Despite these
efforts, projections on plastic production and consumption are alarming.
Therefore, extensive eco-toxicological studies on MPs and NPs need to be
encouraged. Strategic management policies warrant to be framed and
effectively implemented before the society reaches a stage of “no return”.
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