It was recently reported on the news that people ingest a teaspoon, that is 5 grams, of microplastics a week, mainly through drinking water. This news – on Waterforum – for example – was based on a study by Australian researchers. Dutch scientists who do research into microplastics have doubts by this claim: to them 5 grams a week seems unlikley. There had previously been news of an American study into the ingestion of plastics by people that came up with lower numbers. All the more reason to wonder what the status of plastics in (drinking) water is.
Below we answer a few questions about (news about and research into) plastics in water.
What do we know about the Australian research?
The Australian study that was the subject of the latest news reports has not yet been published: the article has been submitted to a scientific journal, but is first being reviewed by other scientists (peer review) before the journal publishes the article. The researchers have given some information about their research method on the website of Newcastle University but how the work is performed will only become apparent when the scientific article is published. In the meantime the WWF has already used the study as a basis for a report and there is mention of ‘your plastic diet’. Foreign media have spoken of ‘a credit card of plastic a week’; see for example the news reports of the Australian Newcastle University and CNN.
What can we say about it at this stage?
Dutch scientists, from KWR and Wageningen University & Research (WUR) and others, would like to know how the Australian researchers came to the conclusion that people ingest around 5 grams of plastic particles a week. Various scientists have looked at the information that the researchers have so far made public, as set out in an EOS article. They express their doubts about the level of the claim; they think that 5 grams a week is unlikely. The Waterforum report also says that the level the Australian researchers have found is significantly higher than what American researchers previously found. Only when the Australian research has been published will it be clear what the calculation is based on and how the researchers have dealt with uncertainties and differences in particle size.
What water are we talking about?
According to the WWF report that is published, water is the greatest source of exposure to plastic for people. However, the report does not make any distinction between tap water and bottled water. The earlier American research showed that particularly bottled water appears to be a source of plastic in the human diet, while water from the tap contains much less plastic particles. When all’s said and done, there are enough reasons to study the presence of plastics in water properly.
What do we know about the Dutch situation?
Various studies have shown that plastics occur in water from sewage treatment, large rivers and lakes in the Netherlands (see below). But no study has systematically looked at plastic particles in drinking water. One of the reasons for this is that the research methods for detecting plastic particles in water are still under development. KWR and other research institutes are currently working on reliable sampling and measuring methods. After all,the reliability and comparability of the methods appears to be an important issue in many studies on this subject. Researchers from the WUR therefore say that much of the research is not yet particularly usable. Despite the uncertainty about how accurate the measurementsare, it is assumed that untreated water contains more particles than water that has gone through water treatment. Research also suggests that groundwater has a lower plastic particle content than surface water. It is highly likely that this is true of the Dutch situation as well.
What do we know about plastics in Dutch surface water?
KWR is keeping a close eye on the developments and is working on behalf of the Dutch water companies on acquiring reliable measurement data on plastic particles in surface water. Within the TRAMP project, for example, plastic particles measured, modelled and their effects are studied specifically for Dutch surface water. Sampling and detection methods have been developed in TRAMP over the last few years. They are being used in different places in the Netherlands in the course of 2019. As a result there will be (more) data available in 2020 about the occurrence of plastic particles in Dutch surface water. Apart from analysing the presence and distribution of particles, KWR is also testing possible solutions, such as The Great Bubble Barrier: a screen at the Wervershoof sewage treatment plant that intercepts plastic particles.
What do we know about plastics in Dutch drinking water?
This year KWR is carrying out an initial study of water samples for the water companies. The results of this research are expected in 2020. A new, more reliable method has been developed for particles with a size of between 0.1 and 0.5 mm. In this method the particles are trapped by a filter and treated to remove organic particles and sand. Then the identity of the particles can be determined. Not only does this provide insight into numbers of particles, but also into types of plastic and sizes of particles; information that can reveal where the plastic particles come from. Ultimately, this enables to compare the level of plastic particles that we ingest through drinking water and compare this to the ingestion through food and air, for example.