## 1 Introduction  
Advanced nanomaterials (NMs) have been widely used in several sectors, from medicine to electronics, aerospace, biotechnology, textiles, agriculture, and, most importantly, in the construction sector [1]. In fact, the nanomaterial market in the European Union (EU) increased from EUR 2.6 billion and 63.3 kilotons in 2016 to EUR 5.2 billion and 141 kilotons in 2020. Metal oxides were the most widely used NMs (88.4% by volume), followed by nanoclays (10.6%), carbon-based NMs (0.5%), dendrimers (0.4%), nanocellulose (0.2%), and metals (0.1%) [2]. Nanomaterials are considered relevant for future employment, financial growth, and technical innovation, as they are materials with high potential to replace (or be added to) conventional materials and chemicals [3; 4; 5; 6]. In fact, nanotechnology has been identified as a Key Enabling Technology, providing the basis for further innovation and new products [7]. The International Organization for Standardization [8] defines a nanomaterial (i.e., size ranges from 1 to 100 nm) as a \"material with any external dimensions in the nanoscale or having internal structure or surface structure in the nanoscale\" [1; 8; 9; 10]. NMs have been designed with various sizes, shapes, crystalline structures, and surface functionalization. Synthesis methods, either bottom-up or top-down, involve physical, mechanical, and chemical processes [11], which can result in different material properties, sizes, and yields [11; 12]. The chemistry and physics of nano-sized construction materials differ from ordinary materials [13] owing to quantum effects and a high surface-to-volume ratio [13]. In fact, the increased surface area of nanostructured materials enhances the availability and thus the reactivity of atoms for interaction with environmental factors or other materials [10; 14]. This capability enables the development of multifunctional materials, such as natural hydraulic lime mortar with titanium dioxide (TiO\({}_{2}\)) addition, incorporating heterogeneous photocatalysis functionality. Such materials can be utilized to combat atmospheric pollution and contribute to the creation of more durable and low-maintenance building facades [15]. Despite the fine-tuning of synthesis methods in recent years, the production and integration of NMs remain more expensive compared to conventional materials. In certain cases, the high cost hinders their widespread application, as in the case of aerogel-based insulation materials [3]. Furthermore, the necessity for upscaling industrial production often poses challenges to the commercialization of nanomaterials [16]. Nevertheless, the growing demand and the optimization of production processes have spurred an increased search for nano-enabled materials [16; 17; 18; 19; 20; 21]. Within this context, EU regulations such as REACH and CLP are challenged to keep up with the rapid development of nanomaterials [22]. Previous studies [23; 24] examining the physical and chemical properties, environmental results, and ecotoxicology of nanoparticles used in construction materials (e.g., nanoclays, aluminum oxide, titanium dioxide, silver nanoparticles, and carbon nanotubes) have concluded that the 2015 OECD report [25] on manufactured nanomaterials lacks comprehensive data and presents an incomplete portfolio [24]. In fact, there is limited literature available that explores the relationship between the physical-chemical properties and toxicity of NMs, which could facilitate the grouping of surface modifications [14]. Considering the current literature gap and the main sustainability pillars, the main objective of this article is to discuss and identify environmental, social (in this case human health), and economic indicators, comparing EU standards for general/conventional materials with a literature review for nanomaterials. The proposed indicators should be mandatory for nanomaterials and can also be employed to achieve a more accurate assessment of sustainability [19; 26; 27].