A character in a famous William Shakespeare play commented that “a great cause of the night is lack of the sun”. (1) Shakespeare used the comment as a statement and a humorous device, which we refer to here as we wish to address reasons why there is perhaps more humor and less illumination in the increasing use of the phrase “potentially toxic element”. Usage of this phrase gained momentum after a 2002 International Union of Pure and Applied Chemist’s publication criticizing the use of the term “heavy metal” to describe metals/metalloids “and their compounds [that] have highly toxic or ecotoxic properties”. (2) The 2002 paper was a scholarly work that carefully analyzed the use of heavy metal in the context of existing definitions, intended meaning, and possible consequences of using a phrase not unequivocally defined to describe hazardous substances. Throwing the proverbial baby out with the baby’s bathwater, we now have the alternative of a less useful phrase. While “toxic element” certainly addresses the concept of toxic and that not all heavy metals are strictly speaking metals, what is not “potentially” toxic? People have died from star fruit poisoning, carrot juice addiction, and water intoxication. (3−5) This global descriptor admits nothing to differentiate the relatively benign iron (Fe), or even sodium (Na), from lead (Pb) and cadmium (Cd), that is, metals toxic at relatively low dosages and simultaneously most frequently referred to as “potentially toxic elements”. Under this “helpful” classifier of “potentially”, we lack a definitive basis for not counting star fruit, carrot juice, or water as potentially toxic, and we, the authors of this Viewpoint, could be said in all factual validity to be potentially intergalactic travelers. As the famous ecological economist Herman Daly pointed out “One way to render any concept innocuous is to expand its meaning to include everything... Any definition that excludes nothing is a worthless definition”; that is, a definition that means everything, means nothing.

This work was supported in part by the National Natural Science Foundation of China (Grant No. 42107245). We thank those who provided constructive commentary for revision of this article, including the editor Prof. Li, one or more anonymous reviewer(s), and D. Phillips.

Peer reviewed