Toxic: What Does It Mean?

This post is approximately one-third pet peeve and two-thirds trying to figure something out.

The pet peeve has to do with the changing meaning of the word toxic. The figuring something out has to do with what its meaning has come to be.

Let’s travel back in time to a dead-tree dictionary, The New Merriam-Webster Pocket Dictionary, dated 1971.

toxic  ’täk∙sik  adj  [L toxicum, n., poison, fr. Greek toxikon arrow poison, fr. toxa bow and arrows, fr. plural of toxon bow] : of, relating to, or caused by poison or a toxin : poisonous

toxin  ’täk∙sən  n : a substance produced by a living organism that is very poisonous when introduced into the tissues but is usu. destroyed by digestive processes when taken in by mouth

Or the 1980 Oxford American Dictionary:

tox∙in (tok∙sin) n.  a poisonous substance of animal or vegetable origin, especially one formed in the body by microorganisms.

From the Web:


Definition of TOXIN: a poisonous substance that is a specific product of the metabolic activities of a living organism and is usually very unstable, notably toxic when introduced into the tissues, and typically capable of inducing antibody formation

But the Merriam-Webster definition of toxic moves away from simply being the adjective associated with toxin, as the 1971 version had it.

Definition of TOXIC

1 : containing or being poisonous material especially when capable of causing death or serious debilitation <toxic waste> <a toxic radioactive gas> <an insecticide highly toxic to birds>

2 : exhibiting symptoms of infection or toxicosis <the patient became toxic two days later>

3 : extremely harsh, malicious, or harmful <toxic sarcasm>

4 : relating to or being an asset that has lost so much value that it cannot be sold on the market

Likewise, from Oxford Dictionaries:

Definition of toxic


1 poisonous: the dumping of toxic waste alcohol is toxic to the ovaries

relating to or caused by poison: toxic hazards toxic liver injury

very bad, unpleasant, or harmful: a toxic relationship

2 Finance denoting or relating to debt which has a high risk of default: toxic debts

denoting securities which are based on toxic debt and for which there is not a healthy or functioning market: the financial system has become clogged with toxic assets



poisonous substances

So the meaning of toxic has changed, but that of toxin hasn’t.  For those of us who learned our chemistry back in the dead-tree days, toxic still carries the connotation of a very poisonous biological product. That’s the pet peeve.

I can deal with words changing meanings. What I have less patience with is imprecise meanings. Toxic is used in so many ways today that I have a hard time knowing what is meant beyond BAD.

Toxic has shifted, within a relatively short time, from referring to a specific class of poisons to a much more general set of meanings. One of those meanings is “poisonous.” The Google Ngram for the usage of the two words shows a great increase in the usage of toxic since about 1940, accompanied by a decrease in the usage of poisonous. Toxic and harmful move in about the same way until about 1970, when toxic takes off and harmful stays constant.

One of the things I look for in judging an author’s credibility is the careful use of words. Toxic is so often used so carelessly that it always attracts my attention. If it’s used to describe a severely poisonous chemical or biological hazard, no problem. But often it’s not possible to infer the degree of hazard from the usage of toxic. Rather, the word itself seems to be the baseline to tell us that a hazard is severe. That would be a fair enough use if the word were always used carefully, in its older single meaning. But it is also used to mean “very bad, unpleasant.”

So we have an example from the October 1 Chemical and Engineering News, who should know better:

An expert contacted by C&EN, who did not want to be identified, agrees that a material showing estrogenic activity on an MCF-7 test isn’t necessarily toxic. “It doesn’t matter if it is estrogenic or not; what matters is whether it causes harm,” the source says.

I have the usual objections to anonymous sources, but the issue here is the word toxic. Estrogenic activity, in the larger context of this article and the concentrations involved, isn’t going to kill anyone. Apparently toxic is being used here as a synonym for harmful, although it’s hard to be sure. This kind of use raises questions in my mind as to whether the author knows what he/she is talking about.

Perhaps a new word was needed to supplement or replace poisonous. But toxic now has so many meanings, and more uses, that it’s hard to know what a writer or speaker means by it. So these days, if it’s used in what seems to be a technical sense, I look for other indicators of the meaning: numbers for how much damages an organism, or a reference to a scientific study.

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