Predicting the contribution of nanoparticles (Zn, Ti, Ag) to the annual metal load in the Dutch reaches of the Rhine and Meuse

• The concentrations of zinc and titanium in Rhine and Meuse have steadily decreased.
• Combining various sources made estimation of nanoparticle releases possible.
• Zinc, titanium and silver nanomaterials contribute 5 to 20% to the river loads.
• Sewage treatment may reduce the contribution significantly.
• Variability in measured concentration makes detection difficult, not impossible.

Although nanoparticles are being increasingly used in consumer products, the risks they may pose to the environment and to human health remain largely unknown. One important reason for this is the lack of quantitative techniques for identifying and measuring the amount of nanomaterials in environmentally relevant circumstances. Such techniques should also discriminate between manufactured and naturally occurring nanoparticles, so that the influence of human activities can be identified.This article describes a technique for estimating nanoparticles by calculating the potential releases of nano-forms of zinc, titanium and silver, the three metals that are widely used for nano-enhanced products, and comparing them to the total loads, based on measurements of the total concentration. We use The Netherlands for our case study.Combining the scarce available data (indicative figures on the content of nanomaterials in various products and usage profiles found in an unrelated category of research) we were able to estimate the total use of such materials in The Netherlands and therefore the potential release into the environment.The calculations indicate that nanomaterials contribute a small but discernible fraction (5 to 20%) to the total loads of zinc and titanium in the Dutch reaches of the Rhine and Meuse. For silver the contribution is at most 3%. The contribution is, however, close to the minimum that can be detected, given the variability in the measured concentrations.