The word "toxic" is meaningless without context
People who don't understand biology weaponize this word to scare you
I’m sure you’ve heard someone say: “oh, I don’t use product [X], that is toxic!”
Maybe you’ve even uttered a similar phrase?
The word toxic evokes fear, worry, and anxiety. And why wouldn’t it? We all know, abstractly, that things that ARE toxic are harmful, right?
The good news is that most of the situations you’re going to encounter these phrases are wildly exaggerated and usually used by people who don’t actually understand the concept of toxicity.
In scientific terms, toxicity refers to an exposure (a substance or a condition) that might cause harm to an organism. This could be direct or indirect harm.
Toxicology is the study of adverse effects of chemical, physical, or biological exposures on living organisms. Toxicology assesses potential hazards, potential risks (recall the difference between hazard and risk here), understanding the mechanisms of potential harms, and managing or mitigating those potential risks.
Scientifically, anything can be toxic at a certain exposure. Anything can be non-toxic at a certain [different] exposure.
The dose makes the poison. With everything.
But let’s expand on that. Toxicity is determined by the exposure itself, the dose (or duration) of exposure, and the route of exposure.
Even substances or exposures that are essential for life or beneficial at a certain dose can become harmful [or toxic] at higher exposures or when exposed through a different route of exposure.
Water is essential for life. But ingesting too much or inhaling it can be fatal.
Water (officially oxidane, if we are using the IUPAC naming system) is essential for life and is composes a majority of our bodies. We must ingest water regularly in order to maintain our health and normally bodily functions.
However, even water can be toxic if you consume too much. Ingesting more than 76 grams of water per kg of body weight in a short period of time can be toxic. It can lead to water intoxication or hyponatremia, both of which can be serious and even fatal.
Water intoxication can lead to symptoms like nausea, vomiting, headache, confusion, seizures, coma or death.
Let’s look at water, this time with a different route of exposure.
We need to ingest water for survival. However, if we inhale water (beyond inhaling water vapor in humid air, for example), that can be fatal at extremely low doses. That is called drowning.
Drowning occurs when someone inhales or aspirates water into the respiratory tract. Water can obstruct the airways and prevent breathing, leading to suffocation. If water reaches the lungs, it interferes with gas exchange (extracting oxygen from the air and exhaling carbon dioxide as a waste product). Water can prevent the alveoli from functioning normally, and can cause hypoxia and hypercapnia. This can lead to respiratory distress. It can progress further to asphyxiation: brain damage, loss of consciousness, and death.
So more specifically, the dosage AND the route of exposure makes the poison.
Eastern Diamondback Rattlesnake venom can be fatal through a snake bite, but poses little risk if you consume it.
Every venomous snake has different venom composition, so each of them would have a completely unique toxicity level. The Eastern Diamondback rattler is the most venomous snake in the US, but globally, is not even in the top 10.
If an Eastern diamondback bites and voluntarily injects venom (yep, snakes do this voluntarily, who knew!), the venom will be deposited intramuscularly, intravenously, or subcutaneously via injection.
Eastern diamondback venom is toxic at an injected dose of 1.2 milligrams per kg of body weight. A bite can deliver up to 1,000 milligrams of venom. So, say you’re a 70 kg person (154 lbs): you only need to receive 84 milligrams of Eastern diamondback venom via injection to experience toxicity. As little as 100 milligrams of venom from this species can be fatal. Mortality can be up to 30% among those who have untreated bites.
Toxicity of this snake’s venom is a result of over 100 different chemicals found in it which have bioactive effects. For the Eastern diamondback, these include an array of chemicals:
Metalloproteinases: enzymes that degrade important structural proteins like collagens, which can cause tissue damage and death, hemorrhage, and facilitate the spread of venom throughout the body.
Phospholipases: enzymes that degrade phospholipids which are specialized fats that make up the membranes of all of our cells.
Serine Proteinases: these act on proteins involved in blood clotting, which can lead to clots where you don’t want them but also bleeding where you don’t want it causing potential strokes and hemorrhages.
Myotoxins: proteins that degrade muscle cells, causing muscle failure, tissue damage, etc.
Neurotoxins: proteins that interfere with nerve signaling, can cause nerve cell death, etc. Symptoms can lead to paralysis, respiratory failure, and potentially death.
and more.
Yes, these are potentially very serious if they get into your tissues and bloodstream through the bite of a snake.
But if you ingest the same dosage of venom, it is unlikely to cause harm, because your stomach acid and proteinases (enzymes that degrade proteins) in your digestive tract would denature these chemicals and digest them into their amino acid subunits.
Yes, even your body is made up of chemicals that COULD be toxic at certain levels.
Life, including human life, is a function of complex networks of chemicals. Proteins in your body? Made of chemicals. Every individual cell that fits together to create your organs, tissues, your entire body? All networks of chemicals.
Yes, your body is thousands of chemicals arranged in complex and intricate ways that make you who you are: a sack of chemicals. And yes, many are the same ones that are used to spread fear about foods, or vaccines, or consumer products in inflammatory and fear-laden posts across social media: formaldehyde, arsenic, alcohols, hydrochloric acid, ammonia, and more.
Again: the dose makes the poison.
While you don’t want to exceed certain dosages of all of these chemicals, many of these are essential for life, or are a function of metabolic processes in your body.
Let’s take formaldehyde, since it is frequently used to fear-monger about vaccines.
There is naturally about 12,000 micrograms of formaldehyde in a pear. An infant produces about 1,100 micrograms daily. Adults? We produce up to 1.5 ounces (42,524 milligrams, 42,524,284 micrograms) of formaldehyde daily as a part of essential metabolic processes.
In contrast, formaldehyde is found in trace levels in vaccines, as a result of some of the purification and inactivation processes during vaccine manufacturing. Less than 100 micrograms would be found in any single vaccine.
That’s 425,000 TIMES less formaldehyde than what an adult produces in their body on a DAILY BASIS.
So, do we need to fear formaldehyde outright? No. Even the levels in our bodies don’t pose a risk. Certainly the levels in vaccines don’t pose a risk.
These examples illustrate the problem: nothing is automatically toxic OR non-toxic.
Non-toxic swaps for household products? That’s a marketing gimmick or straight-up misinformation. Those “non toxic” swaps? They can absolutely be toxic - and many of them at lower doses compared to the alternatives those folks are fear-mongering about, especially if you look at the route of potential exposure.
But people immediately toss logic out the window when claims that evoke fear crop up. We have to combat that tendency: remind yourself that everything is chemicals. Chemicals just are: they aren’t “bad” and they aren’t “good.” Add to that the appeal to nature fallacy: the SOURCE of a chemical means nothing: whether a chemical is naturally-derived or entirely synthetic also has no bearing on the potential risk or safety of the chemical.
What matters? The actual chemical itself, the route of exposure, and the dosage of exposure.
Many chemicals also exhibit tropism: they have a specific mechanism or impact in one species, but not in another.
A common example is glyphosate, because again, it is used so frequently to scare people about food and their health. See here for a detailed piece on this chemical.
For plants, glyphosate inhibits a key enzyme that is required for them to synthesize certain amino acids. However, this enzyme is specific to plants, fungi, and some bacteria: some bacterial species don’t possess it. That’s why in glyphosate-tolerant plants, the plant version of the enzyme is swapped for a bacterial version using genetic engineering technology.
This means: the enzyme ALSO doesn’t exist in humans, so there is no physiological mechanism in which glyphosate would exert that effect in people, even if we were exposed to the chemical at doses required to have that impact.
This is also why when we interpret animal studies, for example, when assessing food chemicals like aspartame, we must factor in inherent physiological differences between rodents, humans, and even non-human primates.
It also underscores why any headlines you see that are summarizing a Petri dish study cannot be taken at face value. You can do ANYTHING to cells growing on a piece of plastic. That doesn’t mean that chemical has any impact in a realistic scenario.
As such, we can FURTHER refine our definition:
The dosage, the route of exposure, the chemical itself, and the mechanism in a certain species makes the poison.
If you hear someone saying some substance is TOXIC without context, know that they are misleading you, either intentionally or unintentionally.
Ask them: at which dosage? In which organism? If it is an insecticide or herbicide, does it have an impact in humans?
These questions help to tease out the reality from the sensational. Too often, sensational and unsubstantiated claims spread like wildlife on social media and through media outlets, but they do not reflect reality.
In this current infodemic of pseudoscience and anti-science rhetoric, we must all do our parts to fact-check and promote critical thinking. And that starts with basic chemistry and toxicology principles.
Improved science literacy benefits public health.
Thanks for joining in the fight for science!
Thank you for supporting evidence-based science communication. With outbreaks of preventable diseases, refusal of evidence-based medical interventions, propagation of pseudoscience by prominent public “personalities”, it’s needed now more than ever.
Stay skeptical,
Andrea
“ImmunoLogic” is written by Dr. Andrea Love, PhD - immunologist and microbiologist. She works full-time in life sciences biotech and has had a lifelong passion for closing the science literacy gap and combating pseudoscience and health misinformation as far back as her childhood. This newsletter and her science communication on her social media pages are born from that passion. Feel free to follow on Instagram, Threads, Twitter, and Facebook, or support the newsletter by subscribing below:
Whoops - forgot to convert all units to micrograms. 425,000 times more formaldehyde in an adult daily than in a single vaccine :)
Great piece.