BTO mansam - BTO 2019.006

Microplastics in (sources for) drinking water. Managementsamenvatting: Over microplastics is nog veel onbekend, maar te verwachten is dat de kleinere deeltjes (nanoplastic) ook het drinkwater zullen bereiken


It becomes more and more clear that plastics can be found in all parts of our environment. All plastics in the environment result from various sorts of human activity such as waste (litter), industrial activities, agriculture applications and household use. The most common types of plastics that have been found in the environment are polyethylene (PE), polypropylene (PP), polystyrene (PS) and PET. Plastics appear in many forms and sizes as can be learned from the fast-growing literature. Plastic particles smaller than 5 mm are commonly defined as microplastics and even smaller particles below one micrometre are referred as nanoplastics. Note that 1 micrometre is a thousandth of a millimetre and 1 nanometer another thousand times smaller (10-9m). This report gathered the findings in the literature on these micro- and nanoplastics with special focus on water and drinking water.
Sampling and measurement. Currently, there are no universally accepted protocols on how to take samples and measure them. Also, the way the findings are reported differ from publication to publication. This impedes comparison of different data sets. Furthermore, there are none or few interlaboratory studies that would enable to evaluate the quality of the currently developed analytical methods, as is common for more classical chemical and microbial analyses. Due to these reasons and due to the fact that particle measurement is still time-consuming as well as laborious, routine measurement is not yet done on a wider scale.
The difficulty of detecting micro and nanoplastics is that these particles may be found everywhere so that contamination may occur during sampling, treatment or analyses. In some cases (especially in drinking water samples) the reported concentration is close to the limit of quantification (LOQ of particles per litre). The LOQ is important because detecting one particle is technically possible but the blanks need to have less particles than the actual sample to be precise on the concentration in the samples when reporting. Note that the limit of detection (LOD) means the lower limit of the particle size, meaning the lowest size range that can be detected.
Waste water. Particle concentrations in influent and effluent can vary from 300 to 1000 p/L and ca. 1 to 50 p/L, respectively. This means that waste water treatment plants (WWTP) remove between 90 to 99% of the plastic particles. Yet WWTPs may discharge billions of particles each day, up to several grams per day. For this estimate it is assumed that roughly 300,000 m3 sewage water per day (size of a modest to large treatment plant) is treated and that only particles larger than 20 micrometre (µm) are taken into account (equivalent to one thousandth of a millimetre). It is safe to assume that the amount of
particles getting into the environment is significantly higher when all smaller particles are also included. This can mean that up to 1000 times more particles could be released, but more reliable estimates are not available.

Microplastics zijn plastic deeltjes kleiner dan 5 mm en nanoplastic is nog vele malen kleiner. De vraag is wat bekend is over deze deeltjes in water. KWR heeft in een Engelstalige rapport gegevens samengebracht uit de wetenschappelijke literatuur over microplastics in afvalwater, oppervlaktewater, grondwater en drinkwater. Uit deze literatuur blijkt dat meetmethoden nog sterk ontwikkeling zijn. Ondanks het feit dat resultaten lastig te vergelijken zijn is het beeld dat microplastics algemeen voorkomen in het milieu en oppervlaktewater (inclusief Nederlandse bronnen voor drinkwater). Ook in drinkwater is nog weinig gemeten, maar enkele studies tonen aan dat ook hier microplastic is aangetroffen (met lagere gehaltes in drinkwater uit grondwater). De betekenis voor de gezondheid van mensen is nog niet goed duidelijk. Over de nanoplastics ontbreekt nog elk inzicht in voorkomen en risico’s. Er zijn te weinig gegevens over het voorkomen en de effecten van nano- en microplastics in milieu en water voor een goed onderbouwde risicoschatting en voor ontwikkeling van verwijderingsmethoden. Dat zal ook nog wel even duren. De onderzoekers adviseren drinkwaterbedrijven zich te blijven inzetten voor een gestandaardiseerde meetmethode en die eerst projectmatig en later meer routinematig in te zetten voor monitoring in bronnen en geproduceerd drinkwater. In afwachting van aanvullende Nederlandse meetgegevens kunnen de gegevens uit het buitenland gebruikt worden als achtergrondinformatie, zoals samengebracht in dit rapport.

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