Nanoparticles (NPs) are widespread in the environment, originating both naturally and from human activities. Anthropogenic NPs are released into the environment as engineered NPs from various applications and as incidental nanoparticles resulting, e.g., from wear, industrial processes, or mining. The latter is of special relevance in Norway, where submarine tailings disposal is a common practice. This study presents the development and implementation of an analytical platform for routine surveillance of NPs in blue mussels (Mytilus edulis) using single particle inductively coupled plasma-mass spectrometry (spICP-MS) [1]. A cost-effective protease mixture suitable for routine applications was utilized for sample digestion. The platform was validated with gold NPs spiked into mussels (Figure 1). The overall method performance was acceptable in comparison to Codex Alimentarius recommendations. Further, an acceptable precision of the method for the detection of Cr-, Cu-, and Ti-containing particles was demonstrated.

The method was applied to examine NP levels in 69 distinct pooled mussel samples from along the Norwegian coastline, considering samples from different environmental contexts, including natural locations, potentially polluted hotspots, and mussel farms [2]. spICP-MS analysis of eleven elements (Ag, Al, Ba, Ce, Cu, Fe, Mn, Pb, Si, Ti and Zr) was performed. NP mass concentrations of a few ng/g up to tens of µg/g and number concentrations of 10⁶ to 10⁹ particles/g (wet weight) were determined. Certain urban and industrially impacted locations were linked to increased levels of Ag-, Pb-, Ce-, Zr-, and Ti-containing NPs, whereas farmed mussels overall exhibited lower concentrations.

Based on the method validation performance and the repeatable identification of environmental hotspots, we concluded that spICP-MS is a suitable method for studying trends in NP levels in seafood for human consumption and the environment. A remaining challenge is the difficulty of ascertaining the trueness of the determined concentrations, especially given the unavailability of certified reference materials and proficiency tests for metal-containing NPs (without and with relevant matrix). It is also crucial to acknowledge the limitations of the spICP-MS technique, such as assumptions about particle composition, density, and shape, and the inability to differentiate individual NPs from those in agglomerated or aggregated states.