Important clarific ations regarding the long -­‐range environmental transport of chemical additives contained in floating plastic debris are presented. -­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐ -­‐-­‐-­‐-­‐-­‐-­‐-­‐ The Perspective article by Gouin1 summarizes various aspects of the environmental long -­‐range transport of plastic particles and non -­‐polymeric chemicals, and also discusses the present knowledge about, and uncertainties associated with, the transport of microplastics (MPs) and additives contained in MPs. However, the article contains many misinterpretations and inaccuracies that lead to incorrect conclusions . We argue therefore that th is Perspective should be seen as an expression of the author’s personal point of view, but should not be used as a source of information in discussions about the long-­‐range environmental transport ( LRET ) of chemical plastic additives. The shortcomings of the Perspective are : 1) Omission of meso -­‐ and macroplastics The Perspective focuses mainly on MPs and overlooks that it is not only MP s that can carry chemi cals. It is mentioned that degradation and fragmentation of larger plastic items is an important source of MPs, but the transport and fate of particles larger than 5 mm is not considered in the P erspective. However, more than three quarters of the plastic debris (by mass) in the Great Pacific Garbage Patch is larger than 5 cm.2 Meso -­‐ and macroplastics are considerable vectors for chemical transport , and reducing the discussion to MP s distorts the overall picture. Even m ore importantly, is has been shown that MP s smal ler than 1 mm may not be easily available for oceanic long -­‐range transport.3–7 This fact is ignored in the Perspective and results of studies that are cited are not related to the LRET of chemical contaminants becaus e they focus primarily on particles smaller than 1 mm (e.g. Dibke et al. (2021)8 and Schernewski et al. (2020)9). # Gouin, T. (2021) Microplastics and Nanoplastics 1 (1), 14. https://doi.org/10.1186/s43591 -­‐021-­‐ 00016-­‐ w. ‡ Accepted for publicatio n in Microplastics and Nanoplastics 2 2) Inappropriate consideration of adsorbed chemicals One of the main statements in the P erspective is “... I perceive that the weight -­‐of-­‐evidence supports exposure to POPs via the LRET of MPs to be minimal relative to other transport pathways, see for instance [24 –27].” While the statement as such is not incorrect, citations 24 to 27 are Zarfl et al. (2010),10 Bakir et al. (2016), Gouin et al. (2011),11 and Koelmans et al. (2016) ,12 all of which address ch emicals that are adsorbed to plastic s. Here the author made a statement about adsorbed chemicals, creating the impression that it would also be relevant for chemicals used as additives in plastics. A key difference is that chemical additives are present in plastic in concentrations higher by several orders of magnitude than concentrations of adsorbed contaminants.13 Conclusions, especially on the mass b alance from studies that only look at adsorbed chemicals , are therefore not relevant and valid for chemical additives. This has already been pointed out by Andrade et al. (2021) , but is not mentioned in the P erspective. Andrade et al. have shown “that appr oximately 8 ,100– 18,900 t of various organic additives are transported with buoyant plastic matrices globally with a significant portion also transported to the Arctic . For many of these chemicals, long -­‐range transport (LRT) by plastic as a carrier is their only means of travelling over long distances without degrading, resulting in plastic debris enabling the LRT of chemicals which otherwise would not reach polar environments with unknown consequences. ” 3) Particulate organic matter is not a good analogue to plastic to learn about LRET It is mentioned in the Perspective that particulate organic matter (POM) has a density and particle size that is similar to that of MPs and that “ hydrological factors that influence the fate of POM in these syst ems, has the potential to influ ence the fate of the MPs in a similar manner. ” This might be correct for shorter time periods. However, POM is biodegradable and will therefore not serve as a vector for the LRET of chemicals. 14 4) View on leaching of plastic additives too narrow The first part of the section “Does plastic represent a source of exposure to plastic -­‐additive chemicals” discusses the diffusion and evaporation of plastic additives out of plastic into air . In comparison to these very detailed explanations, leaching of plastic additives into water or exposed organisms is not described at all (water) or only very briefly (exposed organisms). Especially for very hydrophobic substances, however, leaching into fat and oil is very relevant and clearly more important than diffusion into air . It is therefore necessary to also consid er leaching in the gastrointestinal tract of exposed organisms.15,16 The cases presented in the Perspective, which are intended to show that ingestion of MPs does not represent a significant source of exposure relative to other exposure pathway s, are misleading as they represent substances (nonylphenol and bisphenol A) that are metabolized in fish and probably also in other organisms.17,18 The high concentrations found for bisphenol A and nonylphenol therefore do not result from bioaccumulation but from high exposure levels. This is different for substances such as UV-­‐328 that are only slow ly metaboliz ed.19,20 Experimental results show here that leaching into diges tive fluids of seabirds is a relevant exposure pathway.15,16 5) Inappropriate and unfounded c riticism of the study by Andrade et al. (2021) The Perspective attempts to debase the article by Andrade et al . (2021)21 with incorrect statements. In the P erspective, it is stated that Andrade et al . (2021) used an average weight fraction of 5% for the total of chemical additives associated with plastic debris. However, this is not correct. Andrade et al . (2021)21 used a range of 3% to 7%. It is also stated in the perceptive that the weight fraction adopted by Andrade et al . (2021)21 is likely skewed due to the higher 3 weight fractions of additives associated with polyvinylchloride ( PVC) . However, Andrade et al . (2021)21 explicitly state that there are differences across polymers types and uses and that the range of 3% to 7% “does not cover brominated flame retardants, which are used at around 20% (e.g. BDE -­‐209 in PE [138]), nor plasticisers, which are used in PVC at 33% on average [138].” Gouin himself shows in his Table 1 percentages of additives used across polymer types, easily proving the numbers stated by Andrade et al. (2021) to be rather on the low end of possible total additive concentrations found. There is therefore no reason to discredit the statements and numbers of Andrade et al . (2021),21 as done in the P erspective with the sentence “Caution should thus be used not to overinterpret the significance of the estimates reported by Andrade et al. [133].” 6) Fishing net debris does not necessarily have to be from a local source It is also argued i n the P erspective that fishing -­‐ and shipping-­‐ related materials might be the main source of plastic debris and MP in both surface waters and sediment and that “shipping and/or fishing activity off the coast of remote islands that result in the release and subsequent beaching of plastic debris on their beaches, would, … reflect a local source. ” Here, t he general assumption that fishing and shipping related materials are an important source of plastic debris in the offshore ocean seems to be correct. Lebreton et al. (2018) show ed that 52% of the total floating plastic mass in the Great Pacific Garbage Patch is composed of fishing nets, ropes and plastic lines and 47% of hard plastics, sheets and films. However, a key point in this context is that fishing debris does not automati cally ha ve to be from local source s. Here, we model ed the travel distance and travel time of plastic debris stranding on the beaches of Marion Island and Gough Island, t wo remote islands located in the Sub -­‐Antarctic Indian Ocean and Southern Atlantic Ocean, respectively, where high concentrations of chemical additives have been detected in the preen gland oil of birds. 22 Details on the applied ocean circulati on model, the two scenarios investigated and the results are provided in the Appendix . In brief, t he model show s that plastic debris from river sources is very unlikely to reach Marion Island. Plastic debris from fishing sources reaching Marion Island orig inated mainly from areas s outh of the American continent and fishing grounds near Antarctica . The mean direct distance from sources is 5500 km (range 3250 to 7250 km). Less than 7% of the plastic came from local fishing grounds, west of the island with dis tances to sources less than 1000 km. For Gough Island, the model shows that more t han 99% of the debris from river source s mostly originated from Brazilian rivers, located more than 3000 km away . Plastic debris from fishing sources originated mainly from fishing grounds off the coast of Argentina and travelled on average 4000 km (95 percentile 3000 to 5000 km). These resul ts clearly show that fishing debris does not necessarily have to be from a local source and can undergo LRT. Consequently, plastic-­‐ assoc iated chemicals can undergo LRT as well . 7) The fact that much of the plastic debris from land -­‐based sources remains near the coast does not mean that p lastic debris cannot undergo LRET It is also argued in the Perspective that MPs tend to accumulate in the vicinity of their emission sourc es, based for example on data from Turrell (2020) ,23 “who report results of a model describing the sources of marine plastic litter and MPs to the Scottish Atlantic and North Sea Coast, which are dominated from sources related to littering along the Scottish coast.“ The statement is in line with modelling results from Onink et al. (2021 ),24 who showed that at least 77% of the buoyant marine plastic debris remain within 10 km of the model coastline and that only a small fraction escape s to the open ocean. However, there are two important points 4 here: (i ) Onink et al. (2021)24 stated that the local fraction of beached buoyant marine p lastic debris is relatively low for island s and (ii) e ven if much of the plastic remains near the coast, there is still a proportion that is tran sported into the open ocean and eventually over long distances. The results of Turrell (2020)23 and Onink et al. (2021)24 therefore do not point against the potential of plastic debris to undergo long -­‐range environmental transport. There is additional evidence from monitoring studies that plastic debris undergoes LRET. The International Pellet Watch has shown that plastic pellets, although they deriv ed from land-­‐ based sources, occur on beaches of remote and desert islands such as Macquarie Island and Henderson Island.25 8) The call for better mechanistically -­‐based models is justified , but the existing models describe the transport at least for large fragments in an acceptable way At several points in the P erspective, it is emphasised that not enough is known about the fate and transport of MPs and chemical add itives in MPs to decide whether or not MPs and chemical additives in MPs are able to undergo LRET. It is therefore suggested that “ the development and application of mechanistically -­‐based models and the acquisition of reliable and consistent monitoring data are urgently needed to better identify and characterize the sources, sinks and environmental fate processes of MPs.” We agree that better mechanisti c models are needed to understand the fate of MPs. Consideration s of the size, shape and surface -­‐area to volume ratio are very important to understand the presence of small particles at the surface of the ocean.26,27 Particularly, the surface-­‐ area to volume ratio determines how a particle’s floatability is impacted by bio fouling from organisms or aggregation with natural colloids.28 These processes are rarely considered in 2D transport models where every particle move s with the surface current. This is , however, not so much of a problem when large floating plastics are modeled as they maintain very high rising velocities. Large positively buoyant plastic fragments , with their smaller surface -­‐area to volume ratio s, are less prone to sinking than MPs, so that studying their dispersal over a long period of time as we do here, around one year of tra vel at least, is acceptable. There are still many ways to improve the models also for large plastic debris e.g. by including an interface between wind and current drag, including stokes drift, beaching and others, but the models that exist are able to desc ribe the transport of large plastic fragments , including their LRET potential , in a sufficient way. For example, the modeled accumulation zones are located in the areas where high plastic concentrations have been found empirically .29 9) Perspective calls for points that have already been investigated Finally , we wo uld like to point out that the P erspective often calls for points that have already been investigated . For example, it is stated “If we consider a simplistic model, whereby the relative differences in density be tween PVC and PE are used as parameters that influence mobility, with the density of PVC > PE, then the relative importance of PVC to act as a LRET vector of PACs will be minimal, a ssuming that the greater density of PVC limits mobility and potential exposure to loca tions near emission sources. For plastic additive chemicals t hat may be associated with PE, on the other hand, and for which greater mobility can be assumed based on the simplistic model applied here, we may wish to further consider the influence of kinetic processes, such as leaching rates, which are likely to increase as particle size decreases or, alternatively, as surface area increases.” However, Andrade et al . (2021) have looked exactly into this point and concluded “Highest leaching rates are therefore expected for small PE fragments. According to the equations from Endo et al. [26], the desorption half -­‐life from PE 5 for substances with a log K OW between 5.5 and 7 wil l be between 1 and 38 years, assuming medium -­‐turbulent water (aqueous boundary layer 100 µm). Phthalates have been shown to leach from plastic materials; with 80 –120 ng g–1 plastic over a period of 90 days, o nly a small share of their over all content (1 –5 weight percent) is released in the first 3 months of exposure [91]. This shows that leaching is a relevant process but also that considerable fractions of the additives remain available for long -­‐range transport with the plastic matrix.” Thus, the Perspecti ve often asks for more data or insights but dism isses available information. All of the above points detract from the value of the P erspective as a reliable source, as many of the conclusions are based on inaccurate assumptions and cherry-­‐ picking of avail able information . Therefore, we th ink that the P erspective should not be us ed in discussions of the plastic -­‐driven LRET of chemical additives. Availability of data and material Not applicable Competing interests The authors declare that they have no competing interests. Funding No funding was received for this work. Authors' contributions All authors contributed to the writing of the manuscript. Acknowledgements Not applicable