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Déchets marins et microplastiques

1. Introduction: plastic waste and micro-plastics in the oceans.

    The source document for this Digest states:

    Executive Summary

    A workshop was held at UNESCO-IOC in Paris from the 28th to the 30th of June 2010 as part of GESAMP’s remit to advise its sponsoring agencies (IMO, FAO, UNESCO-IOC, UNIDO, WMO, IAEA, UN, UNEP, and UNDP) on ‘new and emerging issues’ in relation to the state of the marine environment. The invited participants represented the scientific community, the plastics industry, policy makers and environmental NGOs, as well as regional bodies and developing as well as developed countries. The aim was to create a forum where key stakeholders could discuss the broader issues and inform GESAMP on the topic.

    There are two principle sources of micro-plastic particles: i) plastic resin pellets either used in the plastics manufacturing process or purposefully fabricated as abrasives for shot blasting or in cosmetic facial scrubs; and ii) plastic fragments arising from the structural deterioration and disintegration of plastic objects, mainly litter, which can include packaging, articles of clothing, household items such as toothbrushes and razors as well as building materials, lost or discarded fishing and aquaculture gear, amongst many others.

    Given the rise in global plastics production year on year (245 million metric tonnes in 2008), it can be concluded that the input of marine plastic litter, and thereby micro-plastics, will increase in those rapidly developing regions of the world lacking adequate solid waste management practices. There is however a dearth of information on the actual inputs of plastics to the oceans; this needs to be urgently addressed by Governments, municipalities, the plastics industry and multi-national retailers because land-based sources are expected to have a far greater contribution than maritime activities.

    Knowledge of the distribution and fate of micro-plastics is only beginning to emerge. Some recent studies have revealed no significant trend in the concentration of particles in near- surface waters in areas of mid-ocean accumulation (N Pacific and NW Atlantic gyres). In some cases, this may well be due to improvements in sea- or land-based waste management. However, the characteristics and behaviour of the plastic particles may also have a role to play in determining the quantities we are able to sample and measure. For much of the oceans we have little or no information on trends, either at the macro or micro level.

    The advent of compostable (so-called biodegradable) or bio-sourced plastics is expected to have limited effect on either the marine litter or the micro-plastics problem, as the conditions required for their degradation are simply not present in the marine or terrestrial environment.

    It is well documented that plastic litter causes physical harm to marine mammals, fish and invertebrates and instances of death by entanglement, asphyxiation or blockage of organs are common. It is also known that plastic particles tend to accumulate persistent, bioaccumulating and toxic contaminants such as PCBs, DDT and PBDEs. Microplastics have larger surface to volume ratios, potentially facilitating contaminant exchange and have been shown to be ingested by a range of organisms. One of the greatest uncertainties is whether this leads to the bioaccumulation of the contaminant load (absorbed and plastic additives), and hence whether micro-plastics represent an additional and significant vector for transferring pollutants. The conclusion from the Workshop was that this will remain unresolved until the results of additional studies and data collations are available. Recent modelling studies show that the flux to remote areas of contaminants associated with micro-plastics is small compared with that from oceanic and especially long-distance atmospheric transport processes. The difference is that plastics with their accumulated contaminant load are directly ingestible by organisms. A definite cause for concern is that particles, including microplastics have recently been found in the circulatory systems and other tissues of filter feeding organisms such as the blue mussels following experimental exposure and caused typical inflammatory responses. Whether the presence of acid conditions or surface active digestive substances in the guts of such marine organisms can desorb and release contaminants in significant quantities to cause such effects, or whether such a response is to their physical presence, remains to be answered.

    The Workshop recommended that a global assessment of micro-plastics in the context of the marine litter problem as a whole should be initiated under the leadership of GESAMP and with the cooperation of the UN Agencies, Regional and National Administrations, IGO’s and NGO’s in order to further advise policy-makers on the many aspects of the marine plastic debris problem which are currently poorly known and understood. It is recognized that any such assessment would of necessity have to compile data from primary sources including the scientific literature, as few of the available regional assessments provide quantitative data overviews on this topic. Without waiting for all of the unknowns to be filled in, such an assessment will of necessity need to develop agreed methodologies for estimating inputs, distribution, and fate of plastics. The diversity of methodologies for microplastics quantification presently employed requires further standardization in order to ensure data comparability in particular focused on providing estimates of plastics inputs to the oceans. Any such assessment should aim at providing estimates of plastics inputs to the oceans, describe the rates of fragmentation to micro-plastics, as well as their fate and distribution. It should also aim to provide a definitive answer to the scale of the impact both physically and chemically on marine organisms and the potential for impacts on human health from the consumption of these.

    The workshop participants felt that a major effort is required to control plastics in the marine environment and that the issue of micro-plastics and their potential effects in the global oceans is still emerging; despite several regional overviews and a large number of recent papers in the scientific literature, much of the process remains to be discovered. The problems are complex and require a truly multidisciplinary science and engineering approach. The problem of micro-plastics stems clearly from plastic waste entering the oceans and the ultimate solutions are to be found in improved solid waste management on land and at sea; they require the participation of all sectors (politicians, the plastics and retail industry, science, education and the general public). It is hoped that this Workshop report will provide a balanced and reliable perspective as well as a good starting point for such a global assessment. GESAMP would like to thank all the participants who gave generously of their time and ideas both during the workshop and the writing of this report.

    1. Introduction

    1.1 Rationale for holding the Workshop

    This report is the record of a workshop organized by GESAMP as part of its “New and Emerging Issues” Programme. It was held at UNESCO headquarters in Paris from 28 to 30 June, 2010 and hosted by the Intergovernmental Oceanographic Commission (IOC). The workshop was generously sponsored by the Swedish International Development and Cooperation Agency (Sida) and the European Commission, Directorate General for Research. The Workshop agenda is reproduced in Annex I and the list of participants in Annex II.

    GESAMP has a remit to advise its sponsoring UN Agencies on “New and Emerging Issues” in relation to the state of the marine environment. Members of the Joint Group of Experts and its Working Groups may propose new topics for GESAMP to consider in the form of a short proposal. Once approved, GESAMP may appoint a correspondence group to prepare a scoping paper. Upon discussion of the scoping paper, GESAMP with the support of its Sponsoring Organizations may recommend an International Workshop to bring stakeholders together in order to formulate advice on the weight and merits of the issue in question. As a final step, GESAMP may recommend that a Working Group be set up to provide a global Assessment of the topic in order to advise policy makers. The issue of microplastics was first proposed to GESAMP at its 35th session in Accra, 2008, which recommended the formation of a correspondence group to produce a scoping paper and make recommendations. The scoping paper, Micro-plastics and associated contaminants – occurrence and potential impact in the oceans was discussed at GESAMP’s 36th session in Geneva, 2009; (see GESAMP, in press) where it was concluded that the most appropriate next-step was to organize a workshop and encourage participation from a wide variety of sectors (science, industry, regional and global policy and Non-governmental organizations (NGOs). The workshop was therefore designed as a collaborative exercise to include different views from stakeholders. A key objective was also to hear from developing country representatives and from regional bodies directly involved with the problem of marine litter. As the title suggests, the initial focus of this workshop was on plastic particles as a vector in transporting persistent, bioaccumulating and toxic (PBT) substances. Micro-plastics result largely from the presence of plastic debris in the marine environment and in turn, are directly related to the quantities of solid waste entering the oceans from land- and sea- based sources. Once in the sea, a long-term process of transport and deterioration, which is impossible to influence except from the supply side, therefore links our global and regional efforts in solid waste management with the occurrence of micro-plastics in the oceans. The workshop therefore surveyed the broader context of solid waste management, plastic waste recovery and recycling, as well as the behaviour of plastics in the marine environment. This report is a record of these discussions and is intended to lay the groundwork for a possible global assessment in the future and to highlight information gaps. Additional information from the scoping report (GESAMP, in press) and the published literature has been included in some sections to provide further illustration or evidence for topics discussed in the workshop, but the report is not intended to be an assessment of micro-plastic in its own right.

    1.2 Background to assessing the impact of marine micro-plastics

    Marine debris is defined by Galgani et al., (1996) as: any persistent, manufactured or processed solid material discarded, disposed of or abandoned in the marine and coastal environment. A large proportion of marine debris consists of plastics (UNEP, 2009a). The widespread occurrence of macroscopic plastic debris and the direct impact this can have both on marine fauna and legitimate uses of the environment, sometimes remote from industrial or urban sources, has been well documented, e.g. Derraik (2002). In general, plastic debris comes in a wide variety of sizes and compositions and has been found throughout the world ocean, carried by ocean currents and biological vectors (e.g. stomach contents of fish, mammals and birds). Plastics degrade extremely slowly in the open ocean due to their polymeric nature and intended durability and because UV absorption by seawater and relatively low temperatures slow deterioration. In recent years the existence of micro-plastics and their potential impact has received increasing attention, e.g. Arthur et al. (2009). Micro-plastics have a range of compositions and can be demarcated by usage and origin as:

    1. ‘primary’, pellets used as a feedstock in the plastics industry, and in certain applications such as abrasives; and,
    2. ‘secondary’, fragments resulting from the degradation and breakdown of larger items.

    Particles as small as 1 μm have been identified with an arbitrary upper bound of 5 mm based on the propensity to be ingested (Arthur et al., 2009). The global occurrence of plastic pellets in coastal regions began to be reported in the 1970s, (Carpenter et al., 1972; Carpenter and Smith Jr, 1972; Gregory, 1977; Morris and Hamilton, 1974). Laist (1987) was one of the first to review the biological effects of plastic debris. There is increasing evidence that such particles can be ingested by marine organisms, with the potential for: physical disruption and abrasion; toxicity of chemicals in the plastic; and, toxicity of absorbed persistent , bioaccumulating and toxic (PBT) substances. However, the available information still appears to be scarce, experimental studies are few and far between and most of the ocean and coastal areas remains un-sampled.

    Source & ©: ,  Proceedings of the GESAMP International Workshop
    on micro- plastic particles as a vector in transporting persistent, bio- accumulating and toxic substances in the oceans. 28-30th June 2010, UNESCO-IOC,
    Paris. 1. Introduction , p. 10-11


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