Over the years, the pervasive issue of plastic pollution has captured global attention. Among the most concerning aspects of this problem is the prevalence of microplastics. These tiny particles, often invisible to the naked eye, have become a significant environmental concern. Today we will be delving deeper into what microplastics are.

Understanding microplastics

Microplastics are small plastic particles measuring less than 5mm in size. They are typically classified into two categories: primary microplastics and secondary microplastics.

Primary microplastics are intentionally produced at a small size for specific purposes, such as in cosmetics, personal care products or industrial applications. Primary microplastics include items like microbeads, resin pellets (nurdles) and fibres from textiles.

Secondary microplastics result from the fragmentation and breakdown of larger plastic items over time due to weathering, UV radiation and mechanical abrasion. Secondary microplastics are the most prevalent form of microplastic pollution and can originate from a wide range of sources, including single-use plastics, packaging materials and discarded items.

How are microplastics formed?

Primary microplastics are manufactured directly in their small size, but secondary microplastics undergo various processes that lead to their formation:

1.     Fragmentation: Large plastic items such as bottles, bags and fishing nets break down into smaller fragments through physical forces like wave action, sunlight and wind. These fragments continue to degrade into microplastics over time.

2.     Degradation: Plastics exposed to ultraviolet radiation and environmental factors undergo chemical degradation, resulting in the breakdown of the polymer chains. This process weakens the plastic, making it more prone to fragmentation.

3.     Wear and Tear: Microplastics can also arise from the shedding of tiny fibres from synthetic textiles during laundering or general usage. This release of microfibers adds to the overall microplastic pollution.

Microplastic sources

Plastic waste, including discarded packaging materials, synthetic textiles, fishing gear and single-use plastics, constitute major sources of microplastics. Other sources include cosmetic products containing microbeads and plastic pellets used in industrial manufacturing processes. These particles enter our ecosystems through improper waste management, littering and the gradual fragmentation of larger plastic debris. Microplastics enter our environment through multiple sources:

• Fragmentation of larger plastics: Over time, larger plastic items exposed to sunlight, water and physical forces like waves and erosion break down into smaller fragments. These fragments, ranging from microscopic to a few millimetres in size, contribute to the bulk of microplastic pollution.
• Synthetic textiles: Synthetic fabrics, such as polyester, nylon and acrylic, shed tiny fibres during the washing process. These microfibres enter wastewater and find their way into rivers, lakes and oceans.
• Microbeads in personal care products: Some personal care products, including exfoliating scrubs, toothpaste and body wash, have historically contained microbeads made of plastic. These microbeads are designed to provide texture but end up being washed down the drain and eventually enter aquatic environments.
• Industrial processes: Industries that use plastic pellets or powders as raw materials, such as plastic manufacturing, moulding and 3D printing, can release microplastics directly into the environment during production, transportation or waste disposal.
• Atmospheric deposition: Microplastics can also be present in the air we breathe. They may originate from sources like vehicle tyre wear, road markings and the breakdown of plastic litter, which are then carried by winds and settled in various environments, including urban areas and remote regions.

Microplastics are also found in various ecosystems and environmental compartments:

• Marine environments: Oceans, seas and coastal areas are major reservoirs of microplastics. Due to their buoyancy and durability, microplastics can travel long distances, and their concentration is often higher near urban centres, river mouths and areas with heavy maritime activities.
• Freshwater systems: Rivers, lakes and streams receive microplastics from various sources, including urban runoff, industrial effluents and wastewater treatment plants. These water bodies act as conduits for microplastics to reach marine environments.
• Soil and sediments: Microplastics can accumulate in soils through agricultural practices, the application of plastic mulches and the use of sewage sludge as fertilizer. They can also settle in sediments, where they interact with benthic organisms and may affect sediment-dwelling species.
• Drinking water and food: Microplastics have been detected in tap water, bottled water and various food items, including seafood, salt, honey and even beer. Contamination can occur during production, processing and packaging, highlighting the extent of human exposure.

The processing of microplastics

Addressing the microplastic problem requires a comprehensive approach that involves both prevention and effective processing techniques. Several methods are being explored to manage and process microplastics:

• Removal from water sources: Advanced filtration systems and wastewater treatment plants equipped with filters can help capture microplastics present in water sources before they are discharged into rivers, lakes and oceans.
• Mechanical recycling: This process involves sorting and grinding plastic waste into small flakes or granules, which can then be melted and used as raw material for new plastic products. However, due to the small size of microplastics, their separation from other waste materials can be challenging.
• Chemical recycling: In this method, plastic waste is broken down into its molecular components through various chemical processes. This enables the recovery of valuable monomers and polymers that can be used to produce new plastic products, reducing the demand for virgin plastic.
• Biodegradation and bioassimilation: Research is underway to develop biodegradable plastics that can break down naturally over time, reducing the persistence of microplastics in the environment. Additionally, enzymes capable of degrading specific types of plastics are being studied as potential solutions.

Conclusion

Microplastics pose a significant threat to the environment, ecosystems and human health. Understanding the classification, formation and processing of microplastics is crucial in combating this global challenge. Efforts to prevent the release of microplastics into the environment, along with the development of effective processing techniques, are essential steps toward a sustainable future. By adopting a multifaceted approach that encompasses regulation, innovation and consumer awareness, we can work together to reduce the impact of microplastics and create a cleaner, healthier planet for future generations.

Renald Blundell is a biochemist and biotechnologist with a special interest in Natural and

Alternative Medicine. He is a professor at the Faculty of Medicine and Surgery, University

of Malta

Emma Camilleri is currently a medical student at the University of Malta