Delta Life 11

25 We produce 250 billion kilos of plastic worldwide every year. After it has been used, an enormous proportion is not collected properly. It breaks down as litter in the ground, blows away or is left floating in rivers and seas. And we now have hard evidence showing that people ingest plastic as well. How can Deltares help in the struggle with this many-headed monster? T he problem with plastic is not only that it is made from oil: it doesn't decompose regularly, if at all. But once in the environment, it does gradually get broken down. Large pieces of plastic are reduced tomicroplastics and, eventually, to even smaller nano­ plastics. That is precisely where the danger lies: these nanoplastic particles are even smaller than bacteria or viruses and so they can penetrate through our cell walls. Deep in the bodies of humans and animals, they can cause inflammation and disease. As a result of research, and signals from the scientific world and society at large, plastic pollution and its possible consequences are now becoming an in­ creasingly important political issue. The European Union recently stipulated that plastic disposables - such as straws, stirrers and plastic cups - will be banned from 2021 onwards. An example in the Netherlands is that dredged material can now be used only after it has been tested to make sure it is not contaminated with plastic. Microplastics and our health So we know that plastic waste breaks down into ever smaller pieces. We inhale the smallest particles or they end up on the street and get washed into our surface water. They can then enter the food chain through the sea and fish, and eventually end up in our food. What a lot of people don't know is that it is not just the chemicals in plastic that pose a threat to our health and the health of our ecosystems. The fact that plastics are a fertile breeding ground for all kinds of micro-organisms, including possibly pathogenic bacteria, is also a cause for concern. If we swallow or inhale the microplastics, we may be more exposed to infection. Research by Deltares Deltares is working on research into the risks of plastic pollution on several fronts. We are concerned about this form of pollution, too. And it is precisely our knowledge of water and soil systems that could make an important contribution to possible solutions. Which pathogens colonise our plastic waste, where are the risk areas in water systems and how does our immune system respond to this contaminated plastic? Deltares aims to provide answers to these new research questions in the near future in collaboration with researchers from Amsterdam VU-University and Utrecht University Medical Centre. Deltares will be focusing primarily on bacterial colonisation, emissions and the spread of microplastics. Microplastic spread Deltares recently completed a project modelling the spread of plastic particles from car tyres. Vehicles on our roads release large amounts of particles every day, including plastics. Some of this material is spread by the wind and some is washed into the environment with the rain, ending up in ditches, canals, rivers and, ultimately, the sea. Although models always include a margin of un­ certainty, this model shows in detail howmuch BY ASTRID VAN BRAGT / IMAGE HOLLANDSE HOOGTE DELTARES, MARCH 2019