Groundbreaking research reveals low to negligible environmental risk and highlights tyre wear as the major cause in Flanders.
Greater and global attention is being paid to the pollution of water with microplastics. Even so, until recently, relevant research was lacking in Flanders. This matter was addressed on behalf of the Flanders Environment Agency and Flemish Minister of the Environment, Zuhal Demir. Ghent University teamed up with VITO to conduct pioneering research into pollution by microplastics in Flanders. Flemish Minister of the Environment Zuhal Demir: “Despite previous research, we still had many questions in Flanders concerning microplastics. This research outlines the problem, allowing us to take targeted measures to protect our living environment. In fact, it turns out that the sources of microplastics are extremely diverse.”


Plastic products are part of our daily lives and our society depends on them. We are surrounded by plastic products in every imaginable form. Plastics is a growing industry, producing a global total of 368 million tons of plastic in 2019. Sadly, some of this plastic ends up in the world's water and environment. In 2018, this amount was estimated at 86 million tons. Microplastics can be found around the globe in all compartments of the environment, from deep in the ocean to the highest mountain tops, from the North Pole to the salt in our chips. Sunlight, temperature, wave activity and friction in the water cause plastic to fragment into tiny particles, known as microplastics (smaller than 5 mm).

The reason for this study?

With this initiative Flanders is conducting its very first broad and exploratory research investigation into microplastics: what are the different sources, transportation channels, how does the distribution occur in freshwater environments, what is the exposure to humans and animals? 
In the conducted research, a total of 210 samples were gathered from surface water, domestic wastewater, water from wastewater treatment plants and water running off motorways. These samples were analysed and processed using the latest scientific methods. 

The discovered concentrations

First of all, the results confirm that microplastics are widespread in our watercourses, in line with international findings. That is no different in Flanders. In 1 litre of surface water, an average of 0.36 microplastic (MP) particles were identified (concentrations varied between 0 and 4.8 MP/L), of which mainly polypropylene and polystyrene. These polymer types are popular in things such as packaging material. The discovered concentrations are comparable with reported concentrations in the Netherlands, Finland and Hungary. Also, many microplastics sink into the sediment (emerging from the water bed) in our freshwater environments. There we found an average of 2,480 microplastic particles per kg of sediment (between 610 and 9,558 MP/kg). In the sediment, we detected smaller microplastics (25 – 50 µm) than in the surface water. These results are also comparable with data from other European countries, such as Germany and Italy. We witnessed considerable variation, both spatial and temporal. This requires further investigation. 

The possible sources

When considering possible sources of plastic in the environment, we soon think of roadside litter, or large and illegal dumping of plastics by plastic manufacturers or other industrial companies. However, another major contributor to plastic pollution is our domestic wastewater. 
This is why the present study quantified the microplastic concentration in domestic wastewater in Flanders. In our domestic wastewater, we found an average of 10 microplastics per litre of water (9.37 MP per L). In comparison, a relevant study from Scotland reported an average of approximately 16 MPs/L wastewater, which is comparable with these measurements. What this actually means is that for every Flemish person, a daily average of 1,145 microplastics (between 355 and 1634 MPs) end up in our wastewater, amounting to an annual discharge of 418 thousand microplastic particles per Flemish person. The Flemish population therefore produces an annual total of roughly 3,000 kg of microplastics, which end up in our wastewater. 
For 83% of households, this wastewater is transported to a wastewater treatment plant (RWZI). According to this study, it appears that Flemish wastewater treatment plants remove 97.5% (between 92.6 and 100%) of the microplastic particles from the wastewater, before returning it to the local watercourse. These purification percentages are similar to our neighbouring countries. A wastewater treatment plant is therefore an important and indispensable link in the wastewater chain where microplastics can be removed. For households connected to an active wastewater treatment plant, an average of 29 microplastics per Fleming per day therefore still end up in Flemish waterways. Ultimately, 623 kg of microplastic particles from domestic wastewater still end up in the watercourses every year.

One source of microplastic pollution in the environment that was less visible until now are the microscopically small tyre particles released as tyres wear. The particles transferred to the road surface can either end up in the local environment (e.g. verge) or be washed from the road surface by rain and end up in the surface water. Some of the produced particles can also end up in the atmosphere. In order to make a first estimate of tyre particle emissions into the environment, samples were gathered along five Flemish motorways of both the water running off and atmospheric deposits. In the run-off samples, an average of between 0.02 and 9.20 mg rubber particles were discovered per L per day. This equates to an estimated emission of 10.8 mg rubber tyre particles per kilometre travelled. 

In the whole of Flanders, tyre wear causes an estimated 650 tons of rubber particles per year to land on the roads, of which around 250 tons end up in the surface water. This is significantly more than via domestic wastewater. The main route to the surface water is via the run off from (un)tarmacked surfaces, where water is not transported towards the drain. 
Rubber particles were not detected in the rain from air particles, although an average of 3.2 microplastic particles were found to emerge from the air, with a maximum concentration of 8.5 microplastics per m² per day.

Impact on humans and the environment

According to EU methodology, the risks of negative effects of microplastics for the ecosystem are negligible when it comes to surface water. 
We see that microplastics are clearly widespread, however, for the studied compartments, the initial risk analysis for freshwater ecosystems is low to negligible. The risks for the ground organisms (living in and on the sediment) in our watercourses are low to negligible, however in certain zones the risks cannot be excluded. 
Tap water appears to contain a very low number of microplastics (namely between 0 and 0.06 MP per litre). The effects and risks of exposure to microplastics in (drinking) water and food for humans cannot be determined with our current (global) knowledge. This is why Flanders is pushing for further international research.

What will be done with the research?

Flemish Minister of the Environment Zuhal Demir is rather optimistic about the results of this first research. “Microplastics are a huge global challenge, and that's no different in Flanders and the rest of Europe it appears. The fact that the risks of a negative impact on the environment are low or even negligible is good news, together with the fact that 97.5% of the microplastics from wastewater are removed by the wastewater treatment plant. An important source, far more than domestic wastewater, appears to come from our car tyres. That means that any tendency to focus on industry is unjustified. We are all involved in causing microplastics, in our households, transport and industry. That means that in the next steps in the policy we should focus on all the different sectors. If it hadn't been for this study the situation would never have been so clear.”

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