Posted on Categories Discover Magazine
Scientists refer to the study of biological toxins as toxinology (not to be confused with toxicology, with a C—as I explain below). From bacterial toxins like anthrax to the deadliest snake venoms, toxinology examines the chemical warfare between animals, plants, fungi and bacteria. This is the first in a new series I call Toxinology 101, where I explain and explore the fundamentals of toxin science to reveal the unusual, often unfamiliar, and unnerving world created by our planet’s most notorious biochemists.
“Point blank,” my friend, a commander in the US Navy, said firmly, when I asked what misused word or phrase really gets under his skin. “Definitely point blank.”
I asked why, and as he explained, I realized I’d been using the phrase wrong, too. To people familiar with firearms, hearing someone call an up-close gun shot “point blank” is like dragging nails on a chalkboard because that’s not what it means at all. Point blank (which may come from the French phrase pointé à blanc, referring to an arrow being aimed at a white spot at the center of a target) has nothing to do with close proximity to the shooter. Rather, point blank range is the distance at which a weapon aimed at a target succeeds in hitting it—where point of aim (e.g. the middle of the crosshairs) is the same as point of impact.
Bullets don’t travel in a straight line; from the moment they leave the gun, they are pulled by gravity. The further away your target is, the more you have to adjust for the arc of the bullet with the angle of the barrel of the gun. But the aiming line of sight is a straight line; point blank is where the bullet’s path and the line of sight cross. Adjustable sights allow you to aim your shot for a desired distance; thus, for long-range rifles, “point blank” could be set to 100, 200, or even 300+ yards away. Meanwhile, many handguns have fixed sights, so their point blank range is limited to whatever distance the gun is is zeroed to. Point blank range for such guns can be somewhat close—within fifty feet—but even that is much further than what most people think of as ‘point blank.’ In fact, if a gun is literally pressed against the victim, then the point in the middle of the sights (which are usually on top of the barrel) isn’t where the bullet ends up—it’s off by the width of the barrel at least—so that isn’t point blank range. Different munitions have different maximum point blank ranges, depending on the weapon’s inherent ballistic properties, the aiming device used, and the type of bullet used.
It’s no wonder, then, that every time my friend hears someone was shot ‘point blank’ (meaning gun to the head, or within a few feet), he gets a little prickly. Of course, there are words and phrases like “point blank” for every profession. Doesn’t matter if you’re an accountant, mechanic, or CEO, your job requires an understanding of the lingo of your field, and it can be frustrating when words with specific, important meanings are flung about incorrectly by everyone else.
For me, the ‘nails on chalkboard’ feeling comes whenever I hear people talk about their everday exposure to “toxins” or “poisonous” snakes. Though they’re often used interchangeably, the words toxin, venom, and poison (and their corresponding adjectives toxic, venomous, and poisonous) have very distinct meanings to toxinologists. So, it’s only fitting to kick off my Toxinology 101 series by explaining the differences between them and when it’s appropriate to use each of these terms.
Living beings are like machines with trillions of precisely moving parts. Knock a cog or a gear out of sync, and the entire machine can collapse. Toxins are nature’s wrenches; they are substances that disrupt the normal functioning of part(s) of a living creature’s body in a dose-dependent manner in small amounts.
The amount bit is crucial. When we describe the amount of a toxin as “small,” it is a somewhat relative term that relates to quantities that are biologically relevant—such as how much you can eat in a meal or a day, the amount injected by a venomous bite, or how much can be absorbed by your skin. If toxins didn’t require acting at relatively small doses, we’d have to call everything a toxin, because every chemical on the planet can be toxic if enough of it enters your body. Take pure water, for example. Even good ‘ole water can cause harm if you drink enough of it in a short amount of time. Chug several gallons in a few minutes, and you might induce water intoxication, which can be lethal. Still, we don’t consider water a toxin because the volume it takes to cause ill effects is massive.
The key thing to remember is that if it takes a large amount of a substance, especially over time, to cause harm, then it’s not a toxin. So, no, no matter what some so-called ‘babe’ says, you aren’t eating “hidden toxins” every day (yes, there can be toxins in foods, but you’d definitely notice if you were consuming amygdalin in apricot pits or ricin in castor beans). Don’t listen to a guy that changed his middle name to a large, green berry when he says that “gravity is a toxin.” And all those “detox” diets? They’re scams.
If something is a toxin, you can call it toxic. But, of course, this is where things get a bit tricky: while the word toxin only refers to substances that are toxic in low doses, the adjective toxic can be used whenever something causes disease. You can have toxic amounts of water, but water is never considered a toxin. Hence the term toxinology as opposed to toxicology: the latter is the study of adverse effects that occur in living organisms due to chemicals, period. Any chemical in that causes harm no matter how large or repeated a dose required might be examined by toxicologists, while toxinolgists specialize on biologically-produced substances (“biotoxins”) that wreak havoc in small amounts and the biology and ecology of the organisms that wield them. (I could write an entire blog post on the word “chemical,” but let’s just be clear: everything is composed of chemicals. Water is a chemical. So don’t fall for anything that claims to be “chemical-free” either.)
Toxins can be further categorized by where they come from . Usually, toxins that are made synthetically are called toxicants, as opposed to the general term toxins, which occur in nature. Biological toxins are produced by living creatures, while environmental toxins are not (things like lead and arsenic, for example). Toxins also get classified by what they do, especially to us; hemotoxins are toxins that act on the blood, while neurotoxins attack nerves. And then there are subcategories of toxins based on how they enter the body. Oral toxins, for example, are toxins that cause harm when ingested, while topical toxins or are those that are harmful if applied to the skin. Some toxins are harmless if swallowed, but lethal if injected, so the route of entry can matter greatly. In fact, route of entry is so important that toxinologists use entirely separate words to refer to toxins based on delivery: venoms and poisons.
Many animals and plants are equipped with potent toxins to deter potential predators like us. The term used for such toxins depends on how they’re used. It’s kind of like how lawyers use the term “murder weapon” to refer to an object used to kill someone—a paperweight, a knife, or a shoe isn’t a murder weapon (or in two of those cases, a weapon at all) until its used to commit the crime. Well, toxins aren’t referred to as poisons or venoms until how they enter someone’s body has been taken into account. Some of toxins act when ingested, absorbed through the skin, or inhaled; such toxins are referred to as poisons. Others enter our bodies through wounds deliberately inflicted by the toxic species—those are venoms.
Because poisons must be eaten, rubbed on the skin, or breathed in, they’re somewhat “passive” toxins—for the most part, if you’re poisoned, it’s you who did something to cause it. You ate or touched something you really, really shouldn’t have, like an aptly-named poison dart frog, a pufferfish, or certain mushrooms.
The somewhat active role of the intoxicated in poisonings is what sets them apart from envenomations. It essentially boils down to who the aggressor is: the toxic species (venoms) or the one who suffers the effects of the toxins (poisons). Venomous animals and plants by definition are armed with physiological weapons to inflict their terrible chemical cocktails—they bring the toxins to you. It’s entirely possible the only thing someone did to cause an envenomation is unknowingly stray in the general vicinity of a venomous species (though there are certainly times when it’s totally the victim’s fault). Though it’s a bit oversimplified, this comic sums up the difference quite nicely:
The difference between poison and venom is why toxinologists cringe every time they see someone referring to a “poisonous snake.” Most snakes are perfectly fine to handle or eat (I hear they taste like chicken with the texture of fish—which, frankly, sounds delicious), presuming you don’t get stuck with the pointy bits in the process. There are even snakes that can kill you with their venomous bites that are considered delicacies in certain cultures’ cuisines… just ask Gordon Ramsay:
That said, there are exceptions to every rule. Yes, there are some poisonous snakes. The most well studied are the species in the genus Rhabdophis, which are both poisonous and venomous. R. tigrinus, for example, is able to sequester and store toxins from the toads it eats and secrete them on its skin to deter would-be predators. But if warning displays and even poison fail to send a message, the snake is also equipped with a potentially deadly venomous bite.
And then there’s even a third subcategory of toxins, for those who appreciate being as accurate as possible: toxungens. Outlined very succinctly by David Nelsen and his colleagues in their 2014 paper, toxungens are poisons that are aggressively wielded, like the squirting of poison by cane toads or spitting of venom by certain cobra species. Since no wound is inflicted when the toxins are sprayed, they aren’t considered “venoms” in context, but the animals aren’t exactly waiting to be harassed, either. Because the toxic species is actively involved in the delivery of its noxious chemicals, but they aren’t making wounds, we give them a special category all to themselves.
So there you have it. Toxins are substances that cause harm in small amounts. There are three main types of toxins: venoms, poisons and toxungens, which differ based on route of delivery (see the table above). If an animal or plant possesses a toxic chemical cocktail, you can label them with the appropriate adjective(s)—venomous, poisonous, and/or toxungenous. And yes, there are many species which fit into multiple categories, such as poisonous and venomous Rhabdophis snakes or poisonous and toxungenous cane toads. In such cases, you can use whichever terms are most appropriate in context; if you’ve just licked a cane toad to try and get high, for example, poison would be most appropriate word for what you’ve ingested. But if you poked it, and it squirted toxins into your eyes, then you get a gold star for calling the beast toxungenous.
Now that you know the right terminology, I encourage you to go forth and correct your friends, family, and coworkers! Though, I would caution you to do your best to be nice about it. You never know what toxins they might have access to…