## 1 Introduction  
The interest in using building construction materials with better mechanical, durability, and environmental characteristics is continuously growing [1; 2; 3; 4; 5; 6]. However, to obtain such properties, particularly in cement-based materials, some non-conventional raw materials (such as fly ash (FA) and recycled aggregates (RA)), with unknown hazard levels, are being incorporated. Therefore, it is important to determine the ecotoxicological potential of these innovative construction materials and of their raw materials, so that their use and handling are consciously made and contribute to the sustainability of buildings. Toxicology is a multidisciplinary science that studies the harmful effects resulting from the interaction between a toxic agent and a biological system in order to predict the advent of these effects. This science encompasses several areas that, depending on the field, have different names, namely ecotoxicology (or environmental toxicology), which studies the toxic effects of xenobiotics on organisms living in ecosystems [7], and occupational toxicology (or human toxicology), which focuses on the study of the harmful effects caused by chemicals present in the workplace [8]. Toxicology can contribute to technological advancement through the implementation of safe conditions of exposure to given substances [9]. To improve construction sustainability, ecotoxicology may have an important contribution in the assessment of the environmental risk associated with the products to be used in the construction sector. For that purpose, it is necessary to evaluate the products' potential ecotoxicity using leaching tests, ecotoxicity tests, and chemical analyses. The assessment of the environmental contamination risk triggered by the contact between surface and groundwater and the materials is done through leaching tests, which allow assessing the mobility of hazardous substances in aqueous media and their environmental impact, although, by themselves, these tests do not reproduce a real situation. These tests should be supplemented with chemical analyses and ecotoxicity testing using biological parameters to understand the influence of the aqueous extracts (e.g., leachates, eluates) on living organisms. Ecotoxicity tests using the bioluminescent marine bacterium _Vibrio fischeri_ are often used because they are simple, fast, and reproducible. _Vibrio fischeri_ cells emit light when they are healthy, and this luminescence can decrease when the bacterium cells are brought into contact with a toxic agent that causes inhibition of metabolism. This test can be used in the assessment of the potential ecotoxicity of, for instance, leachates or eluates from solid samples like construction materials or ashes [10]. The study by [PERSON] et al. [10] sought to analyse the toxicity of FA and of its elution products to determine the most sensitive bio test in the toxicological assessment and the most effective leaching process. These authors concluded that the _Vibrio fischeri_ test (Microtok test) is suitable for the preliminary screening of solid waste eluate toxicity. However, comparison of data from tests performed with the former bacterium, a freshwater planktonic crustacean _Daphnia magna_ and a freshwater planktonic rotifer _Brachious calyciforus_ indicated _Daphnia magna_ as the most sensitive test organism to assess the ecotoxicity of FA eluates [10]. The study also revealed that FA samples obtained from various coal-fired power plants contain heavy metals, namely: Cr, Cu, Mn, Ni, Pb and Zn. The results of the eluates' chemical analysis in accordance with EN 12457-2 [11] and with the toxicity characteristic leaching procedure (TCLP) [12] indicated that the chemical compounds present in FA can be transferred to the liquid phase depending on the pH of the leaching medium. Thus, the pH of the eluate was also considered an important factor in determining environment contamination and ecotoxicity of FA [10].