Exploring the combined toxicity of boron nitride nanosheets, cadmium and natural organic matter on Daphnia magna.

The increase in anthropogenic activities has led to the release of numerous chemicals and pollutants into aquatic ecosystems, raising significant concerns for water quality and health. Among the emerging issues is the interaction between pollutants and nanomaterials (mixture effects). In this work, it was studied the combined toxicity of boron nitride nanosheets (BNNS) and cadmium (Cd2+) incorporating the influence of natural organic matter (NOM) to enhance ecological relevance for the first time. Colloidal stability studies showed that BNNS is highly unstable, aggregating and precipitating over time in mineral reconstituted water. However, the addition of natural organic matter stabilizes BNNS. Acute toxicity results showed that this material has a good biocompatibility with D. magna, not causing acute toxic effect (immobility) even at high concentration (100 mg L-1). Moreover, when combined with cadmium, BNNS exhibited a "Trojan horse" effect, enhancing Cd2+ toxicity by facilitating its uptake at 1 mg L-1. 48h-EC50 values of Cd2+ and BNNS+Cd2+ were 0.21 and 0.14 mg L-1, respectively. Nevertheless, NOM (10 mg L-1) mitigated this combined toxicity effect after 48 h of exposure. These findings provide novel insights into nanomaterial-pollutant interactions linked to toxicological effects in aquatic environments, contributing to the risk assessment for the safe and sustainable development of the emerging boron nitride nanomaterials and novel products.