Acute and chronic toxicity of metal oxide nanoparticles in chemical mechanical planarization slurries with Daphnia magna†
The semiconductor manufacturing industry uses metal oxide nanoparticles (NPs), including colloidal silica (c-SiO2), fumed silica (f-SiO2), ceria (CeO2), and alumina (Al2O3), as abrasives in chemical mechanical planarization (CMP) processes. Assessing the toxicity of NPs used in commercial CMP slurries is difficult because these mixtures may contain undefined toxic constituents. Herein, the fresh water flea Daphnia magna (D. magna) was used to assess the effects of four model CMP slurries that did not contain known toxic additives. In the acute toxicity assessments, the key findings were that c-SiO2 slurry caused a modest increase in body size indicative of a hormetic stress response, that the Al2O3 slurry was toxic to D. magna with a calculated 96 h LC-50 of 1.1 mg mL−1, that the CeO2 and Al2O3 slurries caused significant dose-dependent decreases in body size, and that NP dissolution was not responsible for these responses. In the chronic toxicity assessments, the key findings were that the c-SiO2 slurry caused a modest increase in reproduction indicative of a hormetic stress response, that the Al2O3 slurry lead to a modest increase in morbidity and a significant decrease in body size, and that the CeO2 and Al2O3 slurries caused dose-dependent decreases in reproductive output. The acute and chronic toxicity results demonstrate that different model CMP slurries exert distinct and unpredictable effects on D. magna morbidity, growth, and reproductive output. Especially important is that the CeO2 and Al2O3 slurries reduced D. magna reproduction upon chronic exposure at low applied doses, which could have adverse consequences to aquatic ecosystems.
- This article is part of the themed collection: Nanomaterials in air