Working Group 40

Working Group 40

Lead agency: Intergovernmental Oceanographic Commission (UNESCO-IOC)

Working Group 40 - Sources, fate and effects of micro-plastics in the marine environment – a global assessment


It is widely recognised that marine debris can have significant ecological, social and economic impacts. Plastics form a large proportion of marine litter, and 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. 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, partly due to UV absorption by seawater and relatively low temperatures. In recent years the existence of micro-plastics and their potential impact has received increasing attention. Micro-plastics have a range of compositions and can be demarcated by usage and source as: i) ‘primary’ micro-plastic resin pellets used in the plastics industry, and in certain applications such as industrial abrasives and skin-care products;  and, ii) ‘secondary’ micro-plastics resulting from the degradation and breakdown of larger items, including so-called biodegradable plastics.

The question of the degree to which micro-plastics and associated chemical loads present a risk to organisms was raised through the GESAMP emerging issues programme. Following the preparation of a scoping paper in 2009, a Workshop was held in June 2010, hosted by UNESCO-IOC in Paris, bringing together experts from industry, academia, NGOs and policy to examine Plastic particles as a vector in transporting persistent, bio-accumulating and toxic substances in the oceans. The proceedings of this Workshop were subsequently published as GESAMP Reports and Studies No. 82 in 2010. One of the recommendations was that GESAMP should carry out a global assessment. This resulted in the creation of Working Group 40 with the following Terms of Reference.

Terms of Reference

1. Assess inputs of micro-plastic particles (e.g. resin pellets, abrasives, personal care products) and macro-plastics (including main polymer types) into the ocean; to include pathways, developing methodologies, using monitoring data, identifying proxies (e.g. population centres, shipping routes, tourism revenues);
2. Assess modelling of surface transport, distribution and areas of accumulation of plastic and micro-plastics, over a range of space- and time-scales;
3. Assess processes (Physical, chemical and biological) controlling behaviour and the rate of production of ‘secondary’ micro-plastic fragments;
4. Assess long-term modelling including fragmentation, seabed and water column distribution, informed by the results of ToR 3;
5. Assess uptake of particles and their contaminant/additive load by biota, as well as their physical and biological impacts at a population level; and
6. Assess the social and economic aspects including public awareness.

In addition to UNESCO-IOC, WG40 is being supported financially and in kind by the International Maritime Organisation (IMO), the United Nations Environment Programme (UNEP), the United Nations Industrial Development Organisation (UNIDO), the National Oceanic and Atmospheric Administration (NOAA), the American Chemistry Council (ACC) and Plastics Europe. At present  (June 2012) there are 16 Core Members of the Working Group.

Microplastics in the ocean - a global assessment - WG 40 Brochure

This brochure summarises the findings of GESAMP Working Group 40, on “Sources, fate and effects of microplastics in the marine environment – a global assessment”. The full assessment  was also published  in the GESAMP Reports & Studies Series earlier in 2015, and can be downloaded below:

Reports and Studies No. 90