• A Method to Assess the Relevance of Nanomaterial Dissolution During Reactivity Testing.

      Peijnenburg, Willie J G M; Ruggiero, Emmanuel; Boyles, Matthew; Murphy, Fiona; Stone, Vicki; Elam, Derek A; Werle, Kai; Wohlleben, Wendel (2020-05-13)
      The reactivity of particle surfaces can be used as a criterion to group nanoforms (NFs) based on similar potential hazard. Since NFs may partially or completely dissolve over the duration of the assays, with the ions themselves inducing a response, reactivity assays commonly measure the additive reactivity of the particles and ions combined. Here, we determine the concentration of ions released over the course of particle testing, and determine the relative contributions of the released ions to the total reactivity measured. We differentiate three classes of reactivity, defined as being A) dominated by particles, B) additive of particles and ions, or C) dominated by ions. We provide examples for each class by analyzing the NF reactivity of Fe2O3, ZnO, CuO, Ag using the ferric reduction ability of serum (FRAS) assay. Furthermore, another two reactivity tests were performed: Dichlorodihydrofluorescin diacetate (DCFH2‑DA) assay and electron paramagnetic resonance (EPR) spectroscopy. We compare assays and demonstrate that the dose‑response may be almost entirely assigned to ions in one assay (CuO in DCFH2‑DA), but to particles in others (CuO in EPR and FRAS). When considering this data, we conclude that one cannot specify the contribution of ions to NF toxicity for a certain NF, but only for a certain NF in a specific assay, medium and dose. The extent of dissolution depends on the buffer used, particle concentration applied, and duration of exposure. This culminates in the DCFH2‑DA, EPR, FRAS assays being performed under different ion‑to‑particle ratios, and differing in their sensitivity towards reactions induced by either ions or particles. If applied for grouping, read‑across, or other concepts based on the similarity of partially soluble NFs, results on reactivity should only be compared if measured by the same assay, incubation time, and dose range.
    • Quantitative human health risk assessment along the lifecycle of nano-scale copper-based wood preservatives.

      Hristozov, Danail; Pizzol, Lisa; Basei, Gianpietro; Zabeo, Alex; Mackevica, Aiga; Hansen, Steffen Foss; Gosens, Ilse; Cassee, Flemming R; de Jong, Wim; Koivisto, Antti Joonas; et al. (2018-06-12)
      The use of nano-scale copper oxide (CuO) and basic copper carbonate (Cu2(OH)2CO3) in both ionic and micronized wood preservatives has raised concerns about the potential of these substances to cause adverse humans health effects. To address these concerns, we performed quantitative (probabilistic) human health risk assessment (HHRA) along the lifecycles of these formulations used in antibacterial and antifungal wood coatings and impregnations by means of the EU FP7 SUN project's Decision Support System (SUNDS, www.sunds.gd). The results from the risk analysis revealed inhalation risks from CuO in exposure scenarios involving workers handling dry powders and performing sanding operations as well as potential ingestion risks for children exposed to nano Cu2(OH)2CO3 in a scenario involving hand-to-mouth transfer of the substance released from impregnated wood. There are, however, substantial uncertainties in these results, so some of the identified risks may stem from the safety margin of extrapolation to fill data gaps and might be resolved by additional testing. Our stochastic approach successfully communicated the contribution of different sources of uncertainty in the risk assessment. The main source of uncertainty was the extrapolation from short to long-term exposure, which was necessary due to the lack of (sub)chronic in vivo studies with CuO and Cu2(OH)2CO3. Considerable uncertainties also stemmed from the use of default inter- and intra-species extrapolation factors.
    • Toxicity of copper oxide and basic copper carbonate nanoparticles after short-term oral exposure in rats.

      de Jong, Wim H; De Rijk, Eveline; Bonetto, Alessandro; Wohlleben, Wendel; Stone, Vicki; Brunelli, Andrea; Badetti, Elena; Marcomini, Antonio; Gosens, Ilse; Cassee, Flemming R (2018-11-19)
      Copper oxide (CuO) nanoparticles (NPs) and copper carbonate nanoparticles (Cu
    • Understanding Dissolution Rates via Continuous Flow Systems with Physiologically Relevant Metal Ion Saturation in Lysosome.

      Keller, Johannes G; Peijnenburg, Willie; Werle, Kai; Landsiedel, Robert; Wohlleben, Wendel (2020-02-12)
      Dissolution rates of nanomaterials can be decisive for acute in vivo toxicity (via the released ions) and for biopersistence (of the remaining particles). Continuous flow systems (CFSs) can screen for both aspects, but operational parameters need to be adjusted to the specific physiological compartment, including local metal ion saturation. CFSs have two adjustable parameters: the volume flow-rate and the initial particle loading. Here we explore the pulmonary lysosomal dissolution of nanomaterials containing the metals Al, Ba, Zn, Cu over a wide range of volume flow-rates in a single experiment. We identify the ratio of particle surface area (SA) per volume flow-rate (SA/V) as critical parameter that superimposes all dissolution rates of the same material. Three complementary benchmark materials-ZnO (quick dissolution), TiO2 (very slow dissolution), and BaSO4 (partial dissolution)-consistently identify the SA/V range of 0.01 to 0.03 h/cm as predictive for lysosomal pulmonary biodissolution. We then apply the identified method to compare against non-nanoforms of the same substances and test aluminosilicates. For BaSO4 and TiO2, we find high similarity of the dissolution rates of their respective nanoform and non-nanoform, governed by the local ion solubility limit at relevant SA/V ranges. For aluminosilicates, we find high similarity of the dissolution rates of two Kaolin nanoforms but significant dissimilarity against Bentonite despite the similar composition.