Research into microplastics in Dutch water

What is the current state of the science?

On 6 September The Guardian published an article on research into plastic fibres in tap water. The research was conducted by Orb Media in collaboration with US scientists, and involved water samples taken in different countries around the world (among them, the US – including the Trump Tower – Lebanon, the UK, Germany and India). No drinking water from the Netherlands was included in Orb Media’s samples. Further inquiries reveal that the underlying scientific paper is not yet available.

KWR is currently conducting research for the Dutch drinking water companies aimed at gaining more insight into the fate of microplastics and nanoplastics in wastewater, surface water and drinking water: researchers Svenja Mintenig, Stefan Kools, Patrick Bauerlein and Annemarie van Wezel are working on the measurement of the smallest possible particles. In the TRAMP research project, financed by TTW (NWO Domain Applied and Engineering Sciences TTW, previously Technology Foundation STW), researchers intend not only to develop a measurement method, but also further investigate whether and how the particles spread in water, the extent to which they are removed by water treatment, and their possible ecological impact.

Are there plastic fibres in Dutch tap water?

Research into plastics in the environment began with the measurement of plastics in seawater, a phenomenon that has come to be known as ‘plastic soup’. More recently, it has become increasingly clear that microplastics can also be found in fresh surface water. These particles originate for instance in personal care products and cleaning products, or result from the breakdown of larger plastics. Research into microplastics at KWR, WUR, Open University and VU University Amsterdam, among others, shows that they are present in rivers like the Rhine and the Meuse, and that treated wastewater is an important source.

Annemarie van Wezel: ‘We need to develop reliable measurement methods. This is the only way that researchers will be able to carry out reliable measurements and other scientists test whether they can replicate the findings. The measurement methods for microplastics have not yet been standardised, and in the case of nanoplastics they are practically non-existent. We also need to pay particular attention to the sampling and sample pre-treatment, to ensure that no extra introduction of plastics occurs: after all, plastics are also present in the air for example.’

Stefan Kools: ‘We are currently working at KWR on measurement methods that are capable of detecting the smaller particles (smaller than 100 micrometres) in water. We have a sampling campaign planned for this year and 2018 within the TRAMP research project. The results of this research will be available next year.’ The measurement method itself is ready and has been submitted for publication in a scientific journal. Researchers will test the method and conduct measurements in wastewater effluent (treated water from wastewater treatment plants), surface water and drinking water. Kools: ‘Although the presence of microparticles in surface water has already been demonstrated, it is not expected that they will reach the groundwater and tap water. To date, measurements in drinking water in the Netherlands have been limited and have not been conducted in a consistent manner. Visible particles are only incidentally detected in drinking water, and frequently following work on the network. It is important that the presence of plastics in water be thoroughly investigated.’

How small is small?

Microplastics are tiny solid plastic particles (smaller than 5 millimetres). The research usually focuses on particles that are still visible, from 100-200 micrometres (i.e., 0.1-0.2 millimetres). For comparative purposes: human hair is about 0.05 millimetres thick and is still just visible to the naked eye. RIVM provides a definition of microplastics on its website.

Research into plastics therefore usually involves particles measuring around 0.2 to 5 millimetres using a microscope. Particles smaller than 0.2 millimetres require special measurement methods, all the more so in the case of the even smaller particles, the ‘nanoplastics’ (1 nanometre is 1/1000 micrometres).

Fibres in the air

The Orb Media research shows pictures of fibres. Fibres can be found in all kinds of water samples. These mostly come from clothing (via washing machines). It is known that fleece sweaters, for example, can be a significant source of fibres. This has been demonstrated by international research; there is no representative Dutch research. Moreover, fibres are also present in the air. Kools: ‘The concern therefore is also that by wearing such clothing while conducting the research, one can oneself release fibres, for example from one’s own sweater, into the samples. This is why one needs to be extra careful when taking samples, and also collect many so-called “blanks”. In this way one can get a clear picture of the concentrations and possible contaminations.’