IVL Swedish Environmental Research Institute

The Swedish Environmental Protection Agency has been assigned to identify important sources of microplastics in the sea and to work for reducing the production and emission of microplastics from these sources. Within the scope of this governmental assignment, IVL Swedish Environmental Research Institute has been funded by the Swedish Environmental Protection Agency to review the sources of microplastics and the pathways microplastics take to reach the sea.

A range of potential sources for microplastics and the pathways by which microplastics can reach the sea were selected for the review. The sources included both intentionally produced plastic pellets and plastic particles formed from fragmentation of larger plastic items. The pathways were primarily stormwater, wastewater and atmospheric deposition. For sea-based sources particles are discharged directly to the sea. Information was collected from scientific articles, reports and through personal communication with experts in relevant areas. Where the available data allowed, calculations were done to quantify the amounts of microplastics.

The most important emissions for microplastics were found to be from road wear and abrasion of tyres. Approximately 13 000 tons of microplastics are released from tyres every year. Since data on microplastic content in stormwater from roads is very scarce it is however uncertain how much of these particles that is transported to water recipients and how much that is permanently deposited in the ground close to the road. The same is true for artificial turfs where the estimated loss was 2 300-3 900 tons per year, but data on the load reaching the sea is completely lacking. Loss of industrially produced plastic pellets in connection to manufacture and handling was estimated to amount to between 300 and 530 tons per year, but also here the volumes discharged to the sea are unknown. For several sources suspected to contribute with large amounts of microplastics to the sea, data is so scarce that no estimations on emissions could be done. This is for example the case for important categories related to waste management, recycling and littering.

In summary it can be concluded that Swedish coastal waters receive substantial amounts of microplastics from both land-based and sea-based sources. Quantitative data is often scarce or completely lacking and it is not possible to summarize the total Swedish discharge of microplastics to the sea. An attempt to rank the sources according to their contribution was made but it should be kept in mind that data suffers from a large degree of uncertainty. Additional studies are needed to improve the bases for further assessments, in particular on microplastics in stormwater from different surfaces and sources.

The aim of the report is to identify and quantify the most important land- and sea-based sources for microplastics found in the marine environment. It is also part of the aim to identify and quantify the most important pathways by which the microplastics reach the sea.