4,677
Views
234
CrossRef citations to date
0
Altmetric
Comments, Opinions, Perspectives

What are heavy metals? Long-standing controversy over the scientific use of the term ‘heavy metals’ – proposal of a comprehensive definition

ORCID Icon & ORCID Icon
Pages 6-19 | Received 20 Oct 2017, Accepted 02 Dec 2017, Published online: 02 Jan 2018
 

ABSTRACT

The term ‘heavy metals’ is commonly used in the environmental literature to refer to metals and metalloids associated with environmental pollution, toxicity and adverse effects on biota. The term has been diversely defined, mostly in terms of density, relative atomic mass and atomic number. This diversity of definitions has raised questions about the nomenclature of these elements. The inclusion of the metalloid As and the nonmetal Se with heavy metals is also an important issue. Some people have called the term as meaningless, imprecise and poorly defined and have suggested abandoning the use of the term. The term itself may not be problematic but the careless and inconsistent use of terminology has led to a confusion about the meaning of the term. The use of the term may be continued but it should be defined in a more comprehensive and scientific way. Here, a more comprehensive definition of the term ‘heavy metals’ is suggested as ‘naturally occurring metals having atomic number (Z) greater than 20 and an elemental density greater than 5 g cm−3.’ A screening of the Periodic Table according to this definition yields 51 elements to be called ‘heavy metals.’ As and Se are excluded from heavy metals.

Acknowledgments

The credit for motivation of this publication goes to Duffus, who published the pioneering and fundamental article in Pure and Applied Chemistry in 2002 and brought the issue into the notice of the scientific community. All those who contributed to the growth and resolution of the controversy on the term ‘heavy metals’ are gratefully acknowledged.

Disclosure statement

No potential conflict of interest was reported by the authors.

Log in via your institution

Log in to Taylor & Francis Online

PDF download + Online access

  • 48 hours access to article PDF & online version
  • Article PDF can be downloaded
  • Article PDF can be printed
USD 61.00 Add to cart

Issue Purchase

  • 30 days online access to complete issue
  • Article PDFs can be downloaded
  • Article PDFs can be printed
USD 2,970.00 Add to cart

* Local tax will be added as applicable

Related Research

People also read lists articles that other readers of this article have read.

Recommended articles lists articles that we recommend and is powered by our AI driven recommendation engine.

Cited by lists all citing articles based on Crossref citations.
Articles with the Crossref icon will open in a new tab.