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What Is The Most Lethal Poison?

World's most lethal poisons


What Is The Most Lethal Poison?

Toxins and poisons can be colorless and odorless. They can be injected into your skin, slipped into food, dissolved in a liquid, or simply released into the air as a dispersible gas. Today we’re going to be exploring some of the world’s most lethal.

How Do You Measure A Poison’s Lethality?

Bottle of Poison

A poison’s lethality is determined by its LD-50. The LD-50 of a substance is the amount that, on average, will kill half of those exposed. A lot of guesswork is involved because actual human tests are not done for obvious reasons. Instead, researchers use lab animals which do not always react the same as humans. A person’s susceptibility can vary depending on tolerance, metabolism, physique, etc. The delivery method of the poison also plays a large role in its effectiveness.

So which are among the top?

One of the world’s most lethal and deadly toxins could be in your very own kitchen cupboard. It’s known as Clostridium botulinum. It is the botulin toxin that causes botulism. This poison is normally encountered through ingestion of contaminated foods, such as unpasteurized canned goods. Botulin is odorless and tasteless which means you wouldn’t know you’ve consumed the LD-50 (0.4 billionth of a gram per kg of body weight) till the paralysis has already set in.

Castor Beans - Ricin

Castor Beans

As far as plant toxins go, ricin is often thought of as the most lethal. Ricin poisoning occurs when a person consumes the beans from a castor plant — the same plant which castor oil is derived. The symptoms are slow to develop, but they can be gruesome. The poison causes your arteries to plug up. Since the blood cannot circulate correctly, your organs begin to “starve”. Death comes usually within a week. If ricin is inhaled or injected, the amount needed to kill you is very small – the amount could fit neatly on the head of a pin.

One highly publicized example of ricin poisoning was in 1978 when the Bulgarian dissident Georgi Markov was assassinated by a James Bond-esque poke from an umbrella. The umbrella was rigged to inject a tiny pinhead sized amount of ricin. Unfortunately, there is no known antidote for ricin poisoning.

What are the most deadly human made toxins?

Sarin attack in Tokyo

Sarin attack in Tokyo

One of the most terrifying neurotoxins is dimethylmercury. This toxin is widely feared because of how easy it can be introduced into your body. Dimethylmercury has even been known to penetrate through thick latex gloves and PVC. In 1996, a chemist by the name of Karen Wetterhahn, unknowingly spilled a single drop onto her fully gloved hand. Symptoms of poisoning didn’t show up until four months later. By the time they did surface, the damage that had already been done was extensive and irreparable. She died six months later.

As far as nerve gasses go, you won’t find many toxins worse than VX and sarin. Sarin is so lethal, that it has been known to kill in less than 60 seconds. It received world attention when the Japanese cult Aum Shinrikyo used it to kill seven people in Matsumoto back in 1994, and 12 more on a Tokyo subway in 1995. VX, which is slightly more deadly than sarin, is thought to have been used by Iraq in 1988 on Iran, and against Kurdish villages in northern Iraq. VX gas was also made popular by the Hollywood blockbuster ‘The Rock’.

Top of the list



Widely regarded as the most deadly, polonium has an LD-50 of 50 billionths per kg of body weight. This means that a single gram of polonium vaporized into the air could theoretically kill up to 1.5 million people. It’s incredibly dangerous due to its intense alpha particle radioactivity. Alpha radioactivity isn’t dangerous when it’s outside of your body – a sheet of paper, or even your thick skin has no trouble stopping the deadly particles. It’s when polonium enters your body that it causes havoc.

Polonium came into the world spotlight when it was used to murder ex-Russian spy Alexander Litvinenko back in 2006.

What is the least detectable poison?

Deuterium Oxide - Heavy Water

Heavy Water

Deuterium oxide arguably holds the title for the least detectable poison in the world. It’s also known as ‘heavy water’. It’s indistinguishable from ordinary water, but has an extra neutron in each hydrogen nucleus.

The extra neutrons interfere with cell processes which can cause death in a matter of weeks. There is nothing to worry about however, Deuterium oxide isn’t cheap and you would need to drink gallons of it within a short period of time for it to have any effect.

Harrison J et al. (2007). “Polonium-210 as a poison“. J. Radiol. Prot. 27
Abu-Qare AW, Abou-Donia MB (October 2002). “Sarin: health effects, metabolism, and methods of analysis“. Food Chem. Toxicol. 40 (10): 1327–33
Pharmacological uses and perspectives of heavy water and deuterated compounds”. Can. J. Physiol. Pharmacol. 77 (2): 79–88
“Botulinum Toxin as a Biological Weapon: Medical and Public Health Management” doi:10.1001/jama.285.8.1059

Photos by USDS, Wikicommons (users lorth2, BrandonLazu) and available under a Creative Commons Attribution license



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