Safe-by-design assessment of SiO2@ZnO multi-component nanomaterial used in construction

Safety aspects of chemicals/materials are transversal in all sustainability dimensions, representing a pillar at early-innovation stages of the European Commission’s “Safe and Sustainable-by-Design” (SSbD) framework for chemicals and materials. The first three of the five SSbD framework steps covers different safety aspects: hazard assessment based on intrinsic properties (step 1), occupational health and safety (including exposure) assessment during the production/processing phase (step 2) and exposure in the final application phase (step 3). The goal of this work was to identify a set of characterization tools/procedures to support the operationalization of the first three safety steps to multi-component nanomaterials (MCNMs), applying the findings to a SiO2 core-ZnO shell MCNM. The safety of this MCNM, used as additive to a silicate/calcium hydroxide mortar to improve air quality through photocatalytic NOₓ removal, was investigated from different perspectives along its value chain. Existing and newly generated data on its hazard profile were collected, workers’ exposure during synthesis was assessed, and potential exposure to hazardous substances during its final application phase was investigated. Concerning step 1, physico-chemical properties, hazard classification and cytotoxicity assays were considered. Afterwards, a three-tiered established methodology for evaluating occupational exposure assessment was performed for step 2. Lastly, for step 3, the release of inorganic substances from the MCNM-based mortars in the final application phase was investigated. Safety assessment according to the SSbD framework was done by selecting tools and procedures suitable for application at an early innovation stage, resulting in a preliminary hazard assessment of the MCNM and a suggestion for redesigning a step in the process.