People have used poisons throughout history for a variety of purposes: to hunt animals for food, to treat diseases and to achieve nefarious ends like murder and assassination.
But what is a poison? Do all poisons act in the same way? Does the amount of the poison matter in terms of its toxicity?
I am a toxicologist who studies how chemicals affect human health, particularly when they cause harmful effects. As a fan of mystery and detective stories, which often feature the use of poisons, I’ve noticed a few poisons that turn up repeatedly in books, television and movies. How they really work is as fascinating as how they’re deployed toward evil ends in fiction.
What is a poison?
The 16th-century physician–alchemist Paracelsus, considered to be the father of toxicology, once wrote: “What is there that is not poison? All things are poison and nothing is without poison. Solely the dose determines that a thing is not a poison.” By this adage, any substance can be a poison with the appropriate amount.
Many people intentionally expose themselves to chemicals like ethanol through alcoholic beverages, nicotine through tobacco products and botulinum toxin through botox treatments at relatively low doses and suffer minimal adverse effects. However, at sufficiently high doses, these chemicals can be lethal. The body’s response often depends on how the chemical interacts with receptors within or on the surface of cells, or how it binds to enzymes used for biological processes. Frequently, higher concentrations of the substance lead to stronger responses.
Despite Paracelsus’ dictum, in popular culture the term “poison” is often reserved for chemical compounds that are not normally encountered in daily life and can lead to detrimental health effects even in relatively small amounts.
At a high enough dose, any chemical could be poisonous.
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Poisons in books, TV and film
Novel writers and television and movie screenwriters have exploited numerous poisons in their works, including those that are chemical elements, such as arsenic and polonium, and those derived from animals, such as snake venom and blowfish poison. Many poisons derived from plants have also been used for villainous purposes in fiction.
In the AMC TV series “Breaking Bad,” high school chemistry teacher Walter White uses a compound called ricin to murder the business executive Lydia Rodarte-Quayle. Ricin is a very potent poison derived from the castor bean Ricinus communis and can be especially lethal if inhaled. Once this compound gets inside a cell, it damages a structure called a ribosome that’s responsible for synthesizing proteins essential to the cell’s function. Ingesting ricin could result in intestinal bleeding, organ damage and death.
