It’s raining plastic in the United States! And elsewhere?

The presence of plastics in polar regions has been recognised by several international research teams. Besides its presence in sediments, seawater and sea ice in the Artic and Antarctica, the presence of plastics in polar ecosystems has also been documented in the diet of the delicate polar fauna, such as fish and zooplankton. In fact, a recent study led by researchers of the University of Coimbra and MARE – Marine and Environmental Sciences Centre, discovered for the first time the presence of microplastics in the diet of penguins. Meanwhile, new studies comproved their presence in other Antarctic species, highlighting that even remote places such as Antarctica are not free from anthropogenic pollution. Plastic has not only direct negative impacts (e.g. death by ingestion or entanglement) but also indirect, by promoting the intake of other pollutants adsorbed by seawater. For that reason, plastic pollution has become an environmental issue of major concern in the last years.

This month I am sharing a recent study that grabbed my attention by its global importance. Entitled “Plastic rain in protected areas of the United States” and led by north-American research teams, this article promotes sustainable policies and practices by discussing the role of rain in the deposition of microplastic particles suspended in the atmosphere. The team analysed the deposition of microplastics in 11 protected and remote areas during 2018. For a better analysis of the results, this team took into account the periods of higher and lower precipitation and other environmental variables such as, proximity to populated centres and the regions’ meteorological context. Apart from dust particles, microplastic presence was detected in 98% of the collected samples. The particle dimensions ranged from 4 micrometres to 3 millimetres, while the vast majority could only be observed using a microscope. Moreover, in periods of higher precipitation the particles found were of bigger size, but less in number, and highly influenced by the direction of air masses and proximity to cities. On the other hand, during dry periods the microplastic deposition was inferior to the dust particles, which may suggest that microplastics can be dispersed to long distances due to its lower density.

Probably you are now questioning yourself: “what is the origin of those microplastics?. In this study the team also analysed the chemical composition of the particles and tried to discover its origin. The majority of particles comprised synthetic fibres of polyester, nylon, polyolefin and other artificial compounds, commonly used in the textile industry for clothing and outdoor gear such as tents, ropes and covers. Regarding clothing, the release of these fibres occurs specially during the drying process, even though some fibres can be released into the wastewater during the washing process. Also, other microplastic particles with spherical and irregular shapes were found. The chemical analysis revealed they were composed by propylene, methyl methacrylate, polyvinyl and other compounds used by industries in the application of coatings and paint. Some of these compounds can be found in personal care products as well. One of the ways these microplastics may entrain the atmosphere may be related with its application using spray aerosols. This study results discuss the role of rain in the deposition of particles and the role that air masses can have in their long-range dispersion.

The negative impact of microplastics is a growing concern due to its possible hazardous outcomes in natural resources’ sustainability (e.g. fisheries), in ecosystem health and in the future of our civilization. For that reason, strong efforts are being done by the scientific community to continue and improve research in microplastics. The long-range dispersion of microplastic to remote regions such as the Arctic and Antarctica highlights the need of awakening social conscience and promote behavioural changes to mitigate plastic pollution.


Source: Brahney J., Hallerud M., Heim E., Hahnenberger M., Sukumaran S. (2020) Plastic rain in protected areas of the United States. Science 368 (6496), 1257-1260. DOI: 10.1126/science.aaz5819

Author: Ricardo Matias


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