The Chemical Entities of Biological Interest (ChEBI) ontology is downloaded weekly from EMBL-EBI at http://www.ebi.ac.uk/chebi/. The data is made available under the Creative Commons License (CC BY 3.0, http://creativecommons.org/licenses/by/3.0/). For more information see: Degtyarenko et al. (2008) ChEBI: a database and ontology for chemical entities of biological interest. Nucleic Acids Res. 36, D344–D350.
Any metal that is characterized by its rather high atomic mass and density. Although typically occurring in low concentrations, they can be found all throughout the Earth's crust (Commonly, a density of at least 5 g cm(3) is used to define a heavy metal and to differentiate it from other, ''light'' metals).