Microplastic is a term that refers to any plastic fragment or particle that is less than 5 mm (0.2 inch) in length. It can be divided into two categories: primary and secondary. Primary microplastic is intentionally produced for various purposes, such as cosmetics, clothing, and industrial abrasives. Secondary microplastic is formed from the breakdown of larger plastic items, such as bottles and bags, due to exposure to sunlight, water, and mechanical forces.

Microplastic is a problem because it is ubiquitous, persistent, and potentially harmful to the environment and human health. It can be found in various habitats, from beaches to oceans, from rivers to soils, and even in the air and drinking water. It does not degrade easily and can persist for hundreds or thousands of years in the environment. It can also act as a carrier of other pollutants, such as heavy metals and organic chemicals, and transfer them to living organisms.

In this article, we will explore the sources, pathways, and impacts of microplastic on living organisms, and the possible solutions to reduce microplastic pollution.

Sources of Microplastic

Microplastic can originate from various sources, both natural and anthropogenic. Some of the major sources of microplastic are:

• Cosmetics and personal care products: Many products, such as toothpaste, shampoo, and face wash, contain microbeads, which are tiny plastic particles that are added for exfoliating or cleansing purposes. These microbeads can be washed down the drain and end up in wastewater treatment plants, where they may not be filtered out completely and enter the aquatic environment.
• Clothing and textiles: Synthetic fabrics, such as polyester, nylon, and acrylic, are made of plastic fibers that can shed during washing or wearing. These fibers can also escape the wastewater treatment plants and reach the water bodies, where they can be ingested by aquatic animals or accumulate in the sediments.
• Industrial activities: Various industrial processes, such as sandblasting, drilling, and cutting, can generate microplastic as a by-product or a waste. These microplastics can be released into the air, water, or land, depending on the disposal methods and the environmental conditions.
• Plastic waste: Plastic waste, such as bottles, bags, and wrappers, can be fragmented into smaller pieces by physical, chemical, and biological factors, such as sunlight, water, and microbes. These pieces can then be transported by wind, water, or animals to different locations, where they can further degrade into microplastic.

The table below shows the estimated global annual emissions of microplastic from different sources, based on a study by Boucher and Friot (2017).

Pathways of Microplastic

Microplastics can travel through different pathways, depending on their size, shape, density, and composition. Some of the main pathways of microplastic are:

• Water: Water is the most common pathway of microplastic, as it can carry microplastic from the land to the sea, or from one water body to another. Microplastic can be transported by surface runoff, rivers, streams, or ocean currents, and can be influenced by factors such as tides, waves, and storms. Microplastics can also sink to the bottom of the water column, where they can be buried in the sediments or resuspended by bioturbation or erosion.
• Air: Air is another important pathway of microplastic, as it can disperse microplastic over long distances and across different regions. Microplastic can be emitted into the air by various sources, such as industrial activities, road traffic, or wind erosion, and can be transported by atmospheric circulation, wind patterns, or precipitation. Microplastics can also deposit on the land or the water surface, where they can be re-entrained by wind or water.
• Animals: Animals can also act as a pathway of microplastic, as they can ingest, excrete, or transport microplastic within or across different habitats. Microplastic can be ingested by animals, either accidentally or intentionally, and can be excreted in their feces or regurgitated in their pellets. Microplastic can also be transported by animals, either externally or internally, and can be transferred to other animals through predation or scavenging.

Impacts of Microplastic

Microplastics can have various impacts on living organisms, depending on their size, shape, composition, and concentration. Some of the main impacts of microplastic are:

• Physical damage: Microplastic can cause physical damage to the digestive systems of animals, such as abrasion, obstruction, or inflammation, which can affect their feeding, growth, reproduction, and survival. Microplastics can also cause physical damage to the respiratory systems of animals, such as irritation, inflammation, or infection, which can affect their breathing, immunity, and health.
• Functional interference: Microplastic can interfere with the normal functioning of animals, such as their feeding, growth, reproduction, and immunity. Microplastic can reduce the food intake and nutritional absorption of animals, by occupying the space or reducing the motility in their digestive systems. Microplastic can also affect the hormone levels and gene expression of animals, by mimicking or blocking the receptors or enzymes involved in their endocrine systems. Microplastic can also impair the immune response and increase the susceptibility of animals to diseases, by inducing inflammation or oxidative stress in their tissues or organs.
• Pollutant transfer: Microplastic can transfer pollutants and pathogens to animals, and potentially affect their health and survival. Microplastic can adsorb or absorb other pollutants, such as heavy metals and organic chemicals, from the surrounding environment, and release them into the tissues or organs of animals, where they can cause toxicity or bioaccumulation. Microplastics can also carry or facilitate the growth of pathogens, such as bacteria and viruses, on their surfaces, and infect the animals that ingest or inhale them.

Microplastics can also affect humans, either directly or indirectly. Humans can be exposed to microplastic through various routes, such as inhalation, ingestion, or skin contact. The health effects of microplastic on humans are still unclear, but some studies have suggested that microplastic can cause respiratory, gastrointestinal, and allergic problems, as well as hormonal disruption and cancer. Humans can also be affected by microplastic indirectly, through its impact on the food chain, the ecosystem services, and the economy.

Solutions to Microplastic Pollution

Microplastic pollution is a complex and global issue that requires collective and coordinated actions from different stakeholders, such as governments, industries, consumers, and researchers. Some of the possible solutions to reduce microplastic pollution are:

• Prevention: Prevention is the most effective and efficient way to reduce microplastic pollution, as it can avoid the generation and release of microplastic at the source. Prevention can be achieved by banning or regulating the production and use of primary microplastics, such as microbeads in cosmetics and personal care products, and promoting natural or biodegradable alternatives. Prevention can also be achieved by reducing the consumption and waste of single-use plastics, such as bottles, bags, and straws, and encouraging reusable or recyclable products.
• Recycling: Recycling is another important way to reduce microplastic pollution, as it can divert plastic waste from the environment and recover valuable resources. Recycling can be improved by enhancing the efficiency and quality of the recycling processes, such as sorting, cleaning, and melting, and developing new technologies to recycle mixed or contaminated plastics. Recycling can also be improved by increasing the demand and supply of recycled plastics, such as by creating incentives and standards for the use of recycled plastics in various products and sectors.

• Removal: Removal is the last resort to reduce microplastic pollution, as it can remove microplastic from the environment and reduce its exposure and impact on living organisms. Removal can be done by developing innovative technologies to degrade or capture microplastic from the water, air, or land, such as using enzymes, bacteria, or nanomaterials to break down microplastic, or using filters, nets, or vacuums to collect microplastic. Removal can also be done by supporting the natural processes that can degrade or sequester microplastic, such as sunlight, waves, or sedimentation.

• Awareness: Awareness is the key to reducing microplastic pollution, as it can increase the knowledge and understanding of the sources, pathways, and impacts of microplastic, and motivate behavioral and policy changes to address this issue. Awareness can be raised by improving the methods and standards for monitoring and assessing microplastics in the environment and living organisms, and sharing the results and findings with the public and the policymakers. Awareness can also be raised by educating and engaging the public and the policymakers on the causes, consequences, and solutions of microplastic pollution, and advocating for more regulations and incentives to reduce microplastic pollution.

Conclusion

Microplastic is a tiny but troubling threat to the environment and human health. It is a widespread, persistent, and potentially harmful pollutant that can affect living organisms in different ways. To tackle this problem, we need to take action at different levels and from different perspectives and work together to reduce microplastic pollution and protect our planet.

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