A Review Conceptual Delimitation of Heavy Metals in Environmental Science VIDICAN Roxana, Tania MIHĂIESCU * , Anca PLEȘA, Ioana CRIȘAN University of Agricultural Sciences and Veterinary Medicine, Faculty of Agriculture, 3-5 Mănăștur Str., 400372 Cluj-Napoca, Romania Received 22 August 2020; received and revised form 5 September 2020; accepted 14 September 2020 Available online 30 September 2020 Abstract Heavy metals have been used by humans for thousands of years. Since ancient times lead was used for pottery glazing while mercury was attributed medicinal properties. Awareness of the danger that heavy metals pose for environment and human health has been gradual. Soils normally contain almost the full range of heavy metals, originating from lithogenic source and from anthropic activity. The first use of the term “heavy metals” in scientific context dates back to 1936. In time has been used as broader concept including elements that cannot be classified as metals or even metalloids. Most definitions given in the past took into consideration only one criteria at a time in defining “heavy metals” and since 1980 many scientists expressed their dissatisfaction for the imprecise delimitation of the concept. Based on a three-way criteria a comprehensive definition limits “heavy metals” to a category of elements that concomitantly are: natural occurring metals, have atomic number >20 and elemental density >5 g/cm 3 . Based on this definition 51 elements from periodic table can be considered “heavy metals”, excluding some such as: Al, As, Se, Ti. Over 20 heavy metals are recognized for the serious health conditions they can induce in humans. Given the increasing pollution in last century, policy efforts are directed towards preventing and limiting heavy metals contamination of the environment, drawing thresholds and requiring remediation. Keywords: pollution, metalloids, toxicity, health, remediation. 1. Defining heavy metals The concept of “heavy metals” has been used to designate certain elements that can have damaging and adverse effects on living systems over a certain threshold [1, 6]. For start, metals are elements with electric conductivity, luster, and malleability that lose electrons to form cations. But heavy metals are not synonymous with toxic metals as many people from the general public might tend to think [3, 7]. Under the concept of “heavy metals” have been often included elements that are not metals, such as As - a metalloid and Se - a non-metal [1]. * Corresponding author. Tel: +40-264-596384 Fax: +40-264-593792 e-mail: tania.mihaiescu@usamvcluj.ro So, the term “heavy metals” has been used often to describe a certain category of pollutants in environmental science and ecotoxicology, and became in time a broader concept until it has been generally adopted as such by the wide public [6]. Examining the beginnings of this term, one can notice that first use of “heavy metals” in a scientific context dates back to 1936 in the work “Inorganic chemistry” translated from Danish into English by Bell and Bjerrum [4]. Many authors since 1980 until today have expressed their dissatisfaction for diversity of definitions from literature and broad use of the term, expressing the need for a harmonized scientific agreement and calling for either the replacement of the term or the narrowing of the concept [1, 4, 5, 6]. Available online at http://journals.usamvcluj.ro/index.php/promediu ProEnvironment ProEnvironment 13 (2020) 82-85 82 brought to you by CORE View metadata, citation and similar papers at core.ac.uk