Definition of Microplastic Size
The term “microplastic” has been widely discussed in recent years, but there are various interpretations of that definition. Microplastics are commonly defined as small plastic fragments [1]. The standard definition categorizes microplastics as particles with a diameter of 5 mm or less; however, alternative definitions include thresholds of 10 mm, 5 mm, or even 2 mm [2]. Among these, the most widely accepted definition describes microplastics as plastic fragments with a diameter of 5 mm or less.
“Plastic Pellets” as Manufactured Microplastics
Microplastics can be classified into two categories: primary microplastics and secondary microplastics. Primary microplastics are intentionally manufactured as small plastic particles, including microbeads used in cosmetics and industrial abrasives, as well as plastic pellets. In contrast, secondary microplastics originate from the degradation and fragmentation of larger plastic products due to weathering, ultraviolet radiation, and wave action in marine and terrestrial environments.
A well-known example of primary microplastics is plastic pellets (Figure 1). These small, granular plastic materials serve as raw materials for manufacturing plastic products. Typically, plastic pellets range in size from 2 mm to 5 mm, overlapping with the upper size limit of the microplastic definition [2].
Issues and Regulations on Plastic Pellets
In the European Union (EU), approximately 57 million tons of plastic pellets were produced in 2021. Estimates suggest that between 52,000 and 184,000 tons of these pellets were released into the environment in 2019 [3]. The main sources of environmental microplastic leakage include accidental spills during transportation and direct emissions from manufacturing facilities [2]. Data indicate that between 3 million and 36 million plastic pellets are released annually from factories into the surrounding environment [3].
In response to this issue, the European Commission proposed regulatory measures in October 2023 to mitigate plastic pellet pollution [4]. These measures prioritize three key strategies for businesses handling plastic pellets: (1) Prevention—minimizing pellet leakage at the source, (2) Containment—preventing leaked pellets from entering the environment, and (3) Recovery—collecting lost or spilled pellets. Implementing these measures is expected to reduce plastic pellet emissions by up to 74%, thereby contributing to a cleaner ecosystem and reducing health risks for both humans and wildlife.
Efforts by Clean Ocean Ensemble
Among the three strategies—Prevention, Containment, and Recovery—this study highlights the significance of Recovery in addressing plastic pollution. While Prevention and Containment focus on minimizing and controlling leakage, the complete elimination of plastic pellet leakage is considered impractical. Therefore, efforts to recover leaked plastic pellets play a crucial role in mitigating environmental contamination. This approach includes beach cleanups and the development of marine litter collection technologies [5]. By emphasizing Recovery, an aspect not fully addressed by the other two strategies, further progress can be made toward reducing plastic pollution in marine ecosystems.
References
[1] Alimba, C.G., Faggio, C., 2019. Microplastics in the marine environment: Current trends in environmental pollution and mechanisms of toxicological profile. Environmental Toxicology and Pharmacology 68, 61–74.
[2] Cole, M., Lindeque, P., Halsband, C., Galloway, T.S., 2011. Microplastics as contaminants in the marine environment: A review. Marine Pollution Bulletin 62, 2588–2597.
[3] Therese, M. K., Lars, A., Göran, B., Bethanie, C., A., Lena, G., Martin, H., 2018. The unaccountability case of plastic pellet pollution. Marine Pollution Bulletin, 129, 52-60.
[4] European Commission, 2023. The Commission proposes measures to reduce microplastic pollution from plastic pellets. Available: https://ec.europa.eu/commission/presscorner/detail/en/ip_23_4984 (Accessed: September 1, 2024).
[5] NPO Hōjin Clean Ocean Ensemble, Hatsuno Kaijō Maikuro Purasutikku no Kaishū ni Seikō [NPO Clean Ocean Ensemble, Successful Offshore Microplastic Recovery Achieved] (in Japanese) | NPO Clean Ocean Ensemble Press Release. https://prtimes.jp/main/html/rd/p/000000014.000110850.html (Accessed: September 1, 2024).
Authors: Ai Mizokami, Shogo Ishiyama, Tomoaki Inoue, Masatoshi Nakakuni