Hazard assessment of W and Mo sulphide nanomaterials for automotive use

Engineered nanomaterials (ENMs) are growing in interest and use due to the enhancements envisaged in many applications. ENM hazard identification and exposure scenarios are growing in interest too. Inhalation, ingestion and assimilation through skin during ENM production or use have to be considered as possible events, and potential ENM toxicity has to be investigated before new ENM-based products are placed on the market. To design new ENM-based additive in lubricants for automotive application, the European FP7 Project AddNano is investigating the use of fullerene-like inorganic nanomaterials, including transition metal disulphides. In this work, the potential toxicities of well-characterized pristine MoS2 and WS2 ENMs were evaluated by in vitro cellular and a cell-free chemical tests. Cytotoxicity and oxidative stress on human pulmonary epithelial cells (A549), ENM surface reactivity (free radical production and lipid peroxidation), and ENM durability in simulated biological fluids were evaluated. In all tests, WS2 did not elicit a response significantly different from the negative control. MoS2 showed a moderate cellular toxicity at the highest dose and was inert in all other circumstances. Both WS2 and MoS2 were soluble in simulated biological fluids, suggesting a short durability in vivo. The low overall biological and chemical reactivity of WS2 and MoS2 suggests that tested nanomaterials are unlikely to be an hazard, as far as human respiratory system is concerned. Data could be usefully implemented in the context of environmental risk assessment and life cycle assessment.