« Heavy Metal » is for Music not for Science!
The use of the term “heavy metals” is still questionned and was proposed to be banned from the scientific literature, why ?
Two years ago, with my colleague Jean-Claude Bollinger, we questioned on the use of the term “heavy metals” : to use or not to use?  and last year i proposed to ban this term from the scientific literature, why ?
In 1980, Nieboer and Richardson had already proposed the replacement of this nondescript term by biologically and chemically significant classification. Moreover, according to the IUPAC, the term “heavy metal” is considered imprecise at best, and meaningless and misleading at worst. The use of this term is strongly discourage, especially as there is no standardized definition of this term.
In 2004, Hodson considered them as geochemical bogey men; In 2007, Chapman first proposed to keep this term for music not for science. In 2010, Hübner et al. proposed to move on from semantics to pragmatics, whereas Madrid recall the long-standing and sometimes forgotten controversy. Nikimnaa and Schlenk further insisted on the ill-definition of the term. In 2012, Chapman continue to wrote on the cacophony not the symphony around heavy metals and Batley et al. further detailed on the usefulness of this term.
Overall, the term “heavy metal” is based on categorization by density or molar mass (zinc or copper have relatively low density and molar mass compared to lanthanides and actinides). It is often used as a group name for metals and metalloids (i.e., arsenic) that are associated with contamination and potential toxicity. The “heavy metals” list is not clearly defined and often mixes metals and metalloids without clear definition. Eventually, the pejorative connotation of “heavy” associated with the toxicity of metal induces a kind of fear amongst society. All so-called “heavy metals” and their compounds may have relatively high toxicity: human exposure to lead by the addition of tetraethyl-lead to gasoline as an antiknock agent, or to lead paint is well documented, however lead–acid battery does not posed direct threat to humans but may generate environmentally hazardous waste. Nonetheless, metals are not always toxic and some are in fact essential: depending on the dosage and exposure levels and the receiving organism/population, it may be essential or toxic. Known for its use in the US five cent coin, nickel is one of the most versatile metals found on Earth. Nickel is essential for life (in some protein) and its deficiency is accompanied by histological and biochemical changes and reduced iron resorption and may lead to anemia.
To be consistent, researchers should only use well-accepted definitions. In the case of “heavy metal”, this term should be replaced by “metal”, “metalloid”, or “trace metal”. The best way to describe the studied elements is clearly to name them or consider them as a group of elements (metals or metalloids).
Here are the updates of some of our figures (Figures 1 & 2; updated from Pourret and Bollinger). The use of the term still increases!
- Olivier Pourret; Jean-Claude Bollinger; “Heavy metal” - What to do now: To use or not to use?. Science of The Total Environment 2018, 610, 419-420, 10.1016/j.scitotenv.2017.08.043.
- Olivier Pourret; On the Necessity of Banning the Term “Heavy Metal” from the Scientific Literature. Sustainability 2018, 10, 2879, 10.3390/su10082879.
- Evert Nieboer; David H.S. Richardson; The replacement of the nondescript term ‘heavy metals’ by a biologically and chemically significant classification of metal ions. Environmental Pollution Series B, Chemical and Physical 1980, 1, 3-26, 10.1016/0143-148x(80)90017-8.
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- Mark E Hodson; Mark Hodson; Heavy metals—geochemical bogey men?. Environmental Pollution 2004, 129, 341-343, 10.1016/j.envpol.2003.11.003.
- Peter M Chapman; Heavy metal-music, not science.. Environmental Science & Technology 2007, 41, 6C, na.
- Ralf Hübner; K. Brian Astin; Roger J. H. Herbert; ‘Heavy metal’—time to move on from semantics to pragmatics?. Journal of Environmental Monitoring 2010, 12, 1511, 10.1039/c0em00056f.
- L. Madrid; “Heavy metals”: Reminding a long-standing and sometimes forgotten controversy. Geoderma 2010, 155, 128-129, 10.1016/j.geoderma.2009.11.031.
- Mikko Nikinmaa; Daniel Schlenk; Uses of phrases. Aquatic Toxicology 2010, 97, 1-2, 10.1016/j.aquatox.2010.02.015.
- Peter M Chapman; “Heavy metal”-cacophony, not symphony. Integrated Environmental Assessment and Management 2012, 8, 216-216, 10.1002/ieam.1289.
- Graeme E Batley; “Heavy metal”-a useful term. Integrated Environmental Assessment and Management 2012, 8, 215-215, 10.1002/ieam.1290.
- Klaus-J Appenroth; What are “heavy metals” in Plant Sciences?. Acta Physiologiae Plantarum 2010, 32, 615-619, 10.1007/s11738-009-0455-4.
- Hazrat Ali; Ezzat Khan; What are heavy metals? Long-standing controversy over the scientific use of the term ‘heavy metals’ – proposal of a comprehensive definition. Toxicological & Environmental Chemistry 2018, 100, 6-19, 10.1080/02772248.2017.1413652.