By Luke Josef Misra –
Introduction.
In recent years microplastics have come to the forefront of media attention. Microplastics, which are defined as plastic pieces less than five millimetres long, are believed to be the most plentiful form of plastic in the oceans [1] at up to 92.4% [2]. A peer reviewed article by Li et al. (2016) discusses how microplastic pollution was tested for in mussels (Mytilus edulis) at 22 sites over 12,400 miles of coastline in China.
Microplastics amongst sediments 1mm scale bar. Martin Wagner et al., CC BY 4.0 via Wikimedia Commons
Why did they look at bivalves?
Bivalves are a class of molluscs that include mussels and are one of the most researched seafood groups [3] because of their filter feeding (filtering plankton out of water) ability. This puts them in direct contact with microplastics. They are also used for their wide geographical distribution [1].
Findings and impact on food security.
Analysis of bivalves found an average number of items of microplastics per individual to be four (ranging from 1.5 to 7.6 items per individual). They also found great variety in the size of the particles dependent on the geographical location, this ranged from less than 250 µm accounting for between 17% and 79%, to more than 1 mm between 1% and 34% of the total microplastics observed [1].
The implications microplastic pollution has for possible disruption to food security (defined by the United Nations committee on world food security as “all people, at all times, have physical, social, and economic access to sufficient, safe, and nutritious food that meets their food preferences and dietary needs”) is the potential risk to safety of food due to trophic transfer [4]. Trophic transfer is in this case is the transfer of microplastics between levels of food chains. Bivalves are commonly consumed by humans globally and often are consumed whole which puts humans at the greatest potential to ingest microplastics. Further it is important to consider the “preference” aspect to the food security definition. With bivalves offering a vital food source particularly in coastal areas [4] and with pescatarian diet preferences claimed by a 4.5% group in one study [5].
What health risks do microplastics have to humans?
Whilst it is believed that humans excrete up to 90% of ingested microplastics [3], the 10% that remain in the body have potential to cause serious effects. There is potential for inflammation due to the stresses microplastics put on cells. There is also possibility with prolonged exposure for necrosis (cell death) to occur in heavily contaminated tissues. There is also some debate towards the possibility of microplastics causing cancer [3].
Conclusion
To conclude Li et al. (2016) extensively observed microplastics within the investigated populations of Bivalves. And there is large scope for potentially destructive impacts to humans when consumed. Food security not only covers the aspects of safety that are brought into question over microplastics but also the potential for limitations over the dietary preference of some groups. There is however more research potential in this area.
References and further reading
[1]: Li, J., Qu, X., Su, L., Zhang, W., Yang, D., Kolandhasamy, P., Li, D. and Shi, H. (2016) Microplastics in mussels along the coastal waters of China. Environmental pollution, 214, 177-184.
[2]: Eriksen, M., Lebreton, L.C., Carson, H.S., Thiel, M., Moore, C.J., Borerro, J.C., Galgani, F., Ryan, P.G. and Reisser, J. (2014) Plastic pollution in the world’s oceans: more than 5 trillion plastic pieces weighing over 250,000 tons afloat at sea. PloS one, 9(12), e111913.
[3]: Lundebye, A.K., Lusher, A.L. and Bank, M.S. (2021). Marine microplastics and seafood: implications for food security. Microplastic in the Environment: Pattern and Process, 131-153.
[4]: Hantoro, I., Löhr, A.J., Van Belleghem, F.G., Widianarko, B. and Ragas, A.M. (2019). Microplastics in coastal areas and seafood: implications for food safety. Food Additives & Contaminants: Part A, 36(5), 674-711.
[5]: Vergeer, L., Vanderlee, L., White, C.M., Rynard, V.L. and Hammond, D. (2020) vegetarianism and other eating practices among youth and young adults in major Canadian cities. Public Health Nutrition, 23(4), 609-619.
