In today’s world, plastics have become one of the most used materials, integrating into our daily lives. These are mainly synthetic polymers, many of which are non-biodegradable, however, current progress has led to the engineering of biodegradable bioplastics. In practical, many processes are available for degrading certain conventional plastics including biodegradation (microbial/enzymatic), thermal and catalytic degradation processes [1,2]. While plastics offer benefits such as being water-resistant, inexpensive, and lightweight, its major drawback is its slow degradation rate, allowing it to linger in the environment for prolonged periods, contributing to the growing issue of plastics waste. Each year, an alarming eight million tons of plastics waste escape from landfills, much of which ends up in our ocean, contributing to marine litter and causing serious environmental pollution [3]. The lack of focus on proper disposal and recycling of plastics has had harmful effects on wildlife and ecosystems. Larger plastics items degrade over time due to environmental factors, resulting in tiny particles known as microplastics (MPs) and nanoplastics (NPs) [[4], [5], [6]]. Plastics particles with size range from 1 μm (i.e. 1000 nm) to 5 mm are considered as microplastics, and extreme smaller particles with sizes smaller than 1 μm are identified as nanoplastics. These MPs/NPs are widespread in marine and terrestrial ecosystems, posing potential harm to environment and human health. Ongoing research has detected MPs/NPs in various food and beverage products as well [7].

MPs can take many forms, including microbeads, microfibers, fragments, and films, each originating from different sources. Their pervasive presence in lakes, rivers, and oceans poses substantial challenges, as they are ingested by organisms ranging from tiny plankton to larger marine animals. Studies have revealed that MPs have been found in the intestines of various species, including molluscs, fish, turtles, and even larger marine creatures, underscoring the severity of the issue. These tiny particles can cause digestive blockages and disrupt the food chain by leaching toxic substances. Additionally, MPs are present in terrestrial and agricultural soils, harming crop productivity and negatively impacting the health of soil microorganisms [8].

MPs are classified into primary and secondary categories depending on their origin. Primary microplastics are tiny synthetic polymers created directly as MPs. They are commonly found in exfoliating scrubs and cleansers, used as grinding agents, are present in the synthetic clothing industry, and are particularly used as microbeads in cosmetics and personal care products. Secondary microplastics result from the fragmentation of larger plastics materials, such as macro- or mesoplastics. This fragmentation happens through various environmental processes, including biodegradation, photodegradation, thermal degradation, and hydrolysis, which reduce larger plastics into smaller particles [9].

The small size of MPs enables them to easily infiltrate containers, food products, soil, and aquatic ecosystems. These non-biodegradable particles present significant risks to marine life and potentially human health [10,11]. Although the physical effects and toxicity of MPs on human health are not thoroughly researched, preliminary findings raise important concerns. The ingestion or inhalation of microplastics into the human body could lead to negative health effects (Fig. 1) [12,13]. Ongoing research is crucial to fully understand the long-term impacts of MPs/NPs, as well as techniques for extracting them from biological systems and methods for their characterization and quantification to safeguard ecological and human health [14,15].

The possible implications of MPs/NPs on people’s health comprise inflammation, DNA damage, oxidative stress, and are an area of growing concern [16,17]. As a consequence of the surface energy associated with their small dimensions, MPs/NPs can carry harmful chemicals and pathogens which further complicates the assessment of their health risks [18]. Although research is still evolving, there is evidence suggesting that MPs/NPs can cause adverse health effects when ingested or inhaled [19]. These particles have been documented in seafood, drinking water, and even the air we breathe [20].

One of the primary contributors to microplastic pollution is the extremely slow degradation rate of plastics, which can take nearly 50 years, and even longer, often over a century, in aquatic environments. Plastics composed of polymer types such as polyvinyl chloride (PVC), polystyrene (PS), polyethylene (PE), polyurethane (PU), polyethylene terephthalate (PET), and polypropylene (PP) etc., are particularly resistant to natural degradation processes. As a result, the type of polymer plays a crucial role in the persistence of microplastics in the environment. These microplastics can become especially hazardous when they adsorb toxic chemicals, leading to chemical toxicity. Beyond their chemical impact, microplastics can disrupt food webs, hinder the growth of primary producers, interfere with essential nutrient cycles such as the nitrogen cycle, and negatively affect the overall functioning of ecosystems. MPs can also influence species interactions and adaptation by interfering with the genetic material of organisms. This interference may lead to gene alterations, DNA damage, and even gene transfer. Microorganisms that colonize MPs can release their genetic material, potentially spreading genetic traits to other species, which may have long-term implications for entire populations. The "plastisphere"- a microenvironment characterized by a high concentration of MPs - can intensify the harmful effects of microplastics. It may serve as a vector for invasive species, facilitate the spread of toxins through food chains, and amplify ecological and toxicological impacts at higher trophic levels [21]. A recently published study shows that the surface charge of NPs significantly influences their toxicological behaviour in the aquatic environment. Positively charged NPs induce stronger oxidative stress and endocrine disruption responses than negatively charged NPs. These charge-specific properties have been related to greater electrostatic interactions with biological membranes [22].

Synthetic plastics are widely used due to their strength, low production cost, and durability; however, they pose significant environmental risks by releasing toxic substances and contributing to pollution. Their resistance to natural degradation has become a major concern, highlighting the need for eco-friendly alternatives. The plastics industry is primarily dominated by six major types of plastics: PE, PP, PVC, PS, PU, and PET, all of which are commonly found in microplastics [23]. Biopolymers, which are natural polymers, offer a promising solution to this issue. They decompose naturally and help in preserving ecosystems, though their high production costs remain a challenge. As a result, biopolymers have become a key area of future research aimed at making them more accessible and practical for global use [24].

MPs have been detected in human blood, the digestive system, and even the brain. This highlights the critical need to develop effective pollution control strategies. Governments should take immediate action to phase out single-use plastics products, promote the use of environmentally friendly alternatives, enhance recycling efforts, and improve waste collection systems. Therefore, it is essential to implement strict laws and regulations to address the growing crisis of microplastics pollution. Some developing countries have already taken steps by banning plastics bags to control this issue. Additionally, ultra-thin plastics (less than 40 microns in thickness) should be targeted for bans, and international policymakers have begun formulating strategies to reduce the use of microbeads [25]. Countries such as the Netherlands and Germany have supported research aimed at understanding terrestrial microplastics, including their distribution, pathways of spread, and potential treatment methods. The United States and France have implemented bans on using primary microplastics. Meanwhile, South Korea has prioritized the development of effective strategies for managing microplastics, introduced plans in 2019 to address microplastics pollution and reduce marine plastic waste [26].

Current research on microplastics reveals several significant gaps, particularly a lack of well-established, standardized methods for their separation, identification, characterization, and quantification. In comparison to aquatic environments, the presence and behaviour of microplastics in terrestrial ecosystems remain largely underexplored. Furthermore, critical areas such as their occurrence, screening, sampling techniques, and associated health risks are still poorly understood [27].

Therefore, this comprehensive review article emphasizes the urgent need for effective control of microplastics pollution, which can only be addressed through advancing research in the areas of separation, characterization, and quantification of microplastics—key objectives of this paper. Additionally, this review underscores that microplastics pollution is not confined to a single nation but represents a global environmental challenge. Since plastics are a human-made product, it is our collective responsibility to take action and find solutions to this growing problem. Additionally, this review focuses on various separation and extraction techniques, including density separation, oil separation, electrostatic separation, magnetic separation, and elutriation, among others. Additionally, it addresses the challenges of characterizing MPs, especially as their size decreases. This review also examined the various characterization techniques, including Fourier Transform Infrared (FTIR) spectroscopy, Raman spectroscopy, Scanning Electron Microscopy (SEM), Laser Direct Infrared (LDIR), and several other methods. The review also discusses quantification techniques, toxicological mechanism and regulatory framework of MPs/NPs.

The graph below (Fig. 2) depicts the annual publication trends in microplastics research, indexed in Fig. 2(a) Web of Science where the x-axis tracks the years from 1995 to 2024 and the y-axis shows the number of publications per year, and Fig. 2(b) Scopus, where the x-axis covers years from 1978 to 2024, with the y-axis indicating the number of publications annually. The data clearly shows a significant upward trend in the total count of publications in recent years, highlighting the increasing interest and focus on microplastics research. In the following section, we have discussed the various microplastics separation techniques utilized in the literature.