KJEMI nr. 5 - 2019

1 1 K J E M I 5 2 0 1 9 So, what happens to MPFs once they enter the environment? Immediately upon entering the marine environ- ment, MPFs are potentially exposed to a complex set of processes that influence where they go and how long they will stay there. You may have seen plastic items change colour or crack when outdoors over a long period of time. The same changes occur to MPFs when exposed to sunlight in the environment. MPFs will gradually increase in brittleness, crack and perhaps fade in colour. 16 Mechanical forces (e.g. waves, wind, interaction with sand or animals) may break the degraded, embrittled MPF into smaller fragments. 16,17 As fragmentation continues, nanoparticles (particles below 100 nm) may eventually be produced. 2 Even when working together under “optimal” conditions, these degradation processes happen very slowly. The rate of degradation and fragmentation is very much influenced by the specific environmental conditions into which the MPFs are released. For example, exposure to lots of UV from natural sunlight will increase the degradation rate, as will a high energy environment.18 However, if the MPFs quickly sink to the bottom of the ocean where there is low energy and no sunlight, degradati- on will occur slowly. 16,18 Importantly, different plastic types have different densities and chemical compositions, which affects whether the particles float or sink in the ocean and ultimately what degrada- tion processes might act upon them. Once they are in the sea, microbiota will colonise MPFs, they can attach to other types of natural particles and be re-packaged into faecal material when ingested. 2,19,20 All of these processes can change how they behave and where they are likely to travel. What happens to animals in environment when MPFs enter it? Marine organisms from zooplankton to larger mammals may directly or indirectly ingest MPFs. 21 MPFs will stay in the digestive system and are not thought to be taken up directly into the tissues of an animal. Little remains known about the toxicity of MPFs, but they may become trapped inside the gut of smaller organisms causing blockage and reducing their ability to feed properly. A recent study condu- cted in the UK and Norway showed that zooplankton ingested MPFs and this caused changes in their growth, behaviour and development. 22 Crucially, smaller MPF frag- ments formed through degradation might be able to accumulate inside organisms. Little is known about the impact of nanofragments on aquatic organisms but they appear to be able to cross biological membranes and accumulate in biological tissues (e.g. gills, lungs). 23,24 It is known that plastics can interact with other chemical pollutants already present in the marine environment. Much less is known about the huge variety of additive chemicals added to plastic products (including MPFs) during manufacturing to impart desirable properties. These chemicals can include UV stabilisers, flame retardants, dyes and intermediates such as bisphenol A (BPA). 25 Some of these compo- unds have proven toxicological effects. Some act as endocrine disrupting chemicals that interfere with normal hormone function in animals. In the marine environment, these potentially harmful chemicals can leach out of plastics and MPFs and become exposed to marine organisms. 26 Few studies have been conducted regarding the leaching of chemical additives from MPs and MPFs and this should be given an increased focus in future research. The Norwegian Research Council (NFR) funded project, MICROFIBRE is investigating the fate of environmental fate and behaviour of microplastic fibres (MPFs), as well as their potential for ingestion and toxicological effects on aquatic species. This project is partnered with a number of Norwegian textile producers who were kind enough to provide test materi- als. Part of this work, focusing on the degrada- tive fate of various MPFs in aquatic environ- ments was presented at MICRO2018 in Lanzarote and partially funded by Norsk Kjemisk Selskap, Faggruppe for Analytisk kjemi. To find more info about the project visit: https://www.sintef.no/en/projects/microfi- bre-evaluating-the-fate-effects-and-mitigat/ ● Figur_3: (Booth, A. M. et al. 2017)