Testing the bioaccumulation of manufactured nanomaterials in the freshwater bivalveCorbicula flumineausing a new test method

Abstract

Increasing amounts of manufactured nanomaterials (MNMs) are produced for their industrial use and released to the environment by the usage or disposal of the products. As depending on their annual production rate, substances are subjected to PBT assessment, the availability of reliable methods to evaluate these endpoints for (corresponding) nanoforms/MNMs becomes relevant. The classical method to elucidate the bioaccumulation potential of chemicals has been the flow-through study with fish, which has limitations as regards meeting the requirements of MNMs. Most MNMs tend to sediment in the aquatic environment. Thus, maintenance of stable exposure conditions for bioaccumulation testing with fish is nearly impossible to achieve when using MNMs. Corbicula fluminea, a freshwater filter-feeding bivalve distributed worldwide, has been previously shown to ingest and accumulate MNMs present in the water phase. To investigate the suitability of C. fluminea for bioaccumulation testing we developed a new flowthrough system to expose mussels under constant exposure conditions. Two nanoparticles (NPs), the AgNP NM 300K and the TiO 2 NP NM 105, were applied. In addition, C. fluminea was exposed to AgNO 3 as a source of dissolved Ag + to compare the bioaccumulation of Ag in dissolved and nanoparticulate forms. For each MNM exposure scenario we were able to determine steady-state bioaccumulation factors. BAF ss values of 31 and 128 for two NM 300K concentrations (0.624 and 6.177 μg Ag per L) and 6150 and 9022for TiO 2 (0.099 and 0.589 μg TiO 2 per L) showed the exposure dependence of the BAF ss estimates. The progression of metal uptake and elimination in the soft tissue provided clear indications that the uptake and thus accumulation is mainly driven by the uptake of NPs and less of dissolved ions.Filter-feeding organisms such as bivalves represent a major target for the bioaccumulation of nanomaterials in the aquatic environment. Therefore, bivalves should be considered as test organisms for the bioaccumulation assessment of nanomaterials. A new flow-through system to expose the freshwater bivalves under constant exposure conditions was developed. Bioaccumulation studies with the freshwater bivalve C. fluminea on two nanoparticles, the AgNP NM 300K and the TiO 2 NP NM 105, demonstrated the suitability of the new test system. The results obtained with this test system can be used to generate useful endpoints required for regulatory purposes and could be included in a tiered bioaccumulation testing strategy for manufactured nanomaterials.

Are Fragrance Encapsulates Taken Up by Aquatic and Terrestrial Invertebrate Species?

“…accordance with previous observations of Wegner et al (2012) with blue mussels exposed to nanostructural polystyrene (Wegner et al, 2012) and Kuehr, Meisterjahn, et al (2020) with C. fluminea exposed to TiO 2 nanoparticles and to gold nanoparticles (AuNPs). Also in these studies an increased filtration activity and release of feces or pseudo feces were observed (S. Kuehr, Meisterjahn, et al, 2020;Wegner et al, 2012).…”

Ingestion of bivalve droppings by benthic invertebrates may lead to the transfer of nanomaterials in the aquatic food chain

“…Similarly, Kuehr et al [46] observed an enrichment of suspended TiO 2 NPs in the freshwater bivalve C. fluminea with an accumulation factor of more than 9000 that was followed by a complete elimination of the TiO 2 load within 24 h of depuration. This was explained by the rapid and effective release of F/pF containing the previously enriched TiO 2 NPs [46]. Therefore, filter feeding bivalves may play an important role in the exposure of benthic species that feed on the F/pF as described above.…”

“…Although the released F/pF were not analyzed for the nPS content, it is likely that the suspended nPS were ingested, concentrated, and finally eliminated by the release of F/pF. Similarly, Kuehr et al [46] observed an enrichment of suspended TiO 2 NPs in the freshwater bivalve C. fluminea with an accumulation factor of more than 9000 that was followed by a complete elimination of the TiO 2 load within 24 h of depuration. This was explained by the rapid and effective release of F/pF containing the previously enriched TiO 2 NPs [46].…”

The bioaccumulation testing strategy for manufactured nanomaterials: physico-chemical triggers and read across from earthworms in a meta-analysis

“…47 The bioaccumulation potential of TiO 2 NPs and SWCNTs was also assessed in a sediment dwelling marine polychaete using ICP-OES. 48 More recently the technique of single particle ICP-MS (spICP-MS) has being used, in addition to total metal concentrations measurements of Ag NPs and TiO 2 NPs, to determine particle concentration during metal uptake and elimination from a freshwater bivalve, 49 and from an amphipod, Hyalella azteca. 50 The methods used in these available data sets on aquatic invertebrates might require further validation to enable a standardised protocol for the tissue detection of MNs in a technical guidance document.…”