Top 10 worst toxic substances

Toxicity is usually measured in mouse units (MU), representing a dose of toxin that kills 50% of mice (LD50) when exposed to the toxic substance. In the following list, ten of the most acute substances are ordered from least to most severe, a lethal dose for a 90kg individual is also shown. Although there are a lot more toxins and toxicants, these ten are well known and vary a lot in their respective lethal dose.

Lethal dose: aprox. 18 grams

Though achieving lethal dose with caffeine would be exceptionally difficult with regular coffee unless you're really trying to commit suicide, there have been reported deaths from overdosing on caffeine pills, with serious symptoms of overdose requiring hospitalization occurring from as little as 2 grams of caffeine. In cases of much larger overdoses, mania, disorientation and psychosis may occur; also rhabdomyolysis (breakdown of skeletal muscle tissue) can be provoked.

Lethal dose: aprox. 4 grams

Heroin, a semi-synthetic opioid drug synthesized from morphine, a derivative of the opium poppy. As with other opioids, heroin is used as both a pain-killer and a "recreational drug" and has an extremely high potential for abuse. Frequent and regular administration is associated with tolerance, moderate physical dependence, and severe psychological dependence. The name was derived from the German word "heroisch", due to its perceived "heroic" effects upon a user. However, it was chiefly developed as a morphine substitute for the coughs that did not have its addictive side-effects.

Lethal dose: aprox. 1,5 grams

Dendrotoxins inhibit neurotransmissions by blocking the nerve impulses, in other words, paralyses the nerves. The victim of a black mamba bite soon experiences a tingling sensation in the mouth and limbs, dizziness, erratic heartbeat, double vision, severe confusion, fever, excessive perspiration, and lack of muscle control, among other symptoms. If the victim does not receive medical attention, symptoms rapidly progress to severe abdominal pain, shortness of breath, shock, and paralysis. Eventually, the victim experiences convulsions, cardiac arrest, respiratory arrest, coma, and finally, death.

Lethal dose: aprox. 2 g

Arsenic and many of its compounds are especially potent poisons. Arsenic disrupts intracellular energy transfer through several mechanisms, inhibits lipoic acid which leads to insufficient cellular and mitochondrial respiration. These metabolic interferences lead to death from multi-system organ failure, probably from necrotic cell death. Although arsenic causes toxicity, it can also play a protective role in leukemia treatment.

Lethal dose: aprox. 1,3 grams

Most famous for spy movies and WWII documentaries; cyanide makes the cells of an organism unable to use oxygen. High concentrations of cyanide causes a coma with seizures, apnea and cardiac arrest, with inevitable death following in a matter of minutes. At the first stages of unconsciousness, breathing is often sufficient or even rapid, although the state of the victim progresses towards a deep coma, sometimes accompanied by pulmonary edema, and finally cardiac arrest. Skin color goes pink from cyanide-hemoglobin complexes.

Lethal dose: aprox. 0,003 grams

Also known as "tetrodox" and frequently abbreviated as TTX, it's a potent neurotoxin with no known antidote. The toxin can be found on some western newts and puffer fishes among other animals. It causes paralysis; many victims are unable to move. The victim, although completely paralyzed, may be conscious and in some cases completely lucid until shortly before death. Death usually occurs within 20 minutes to 8 hours.

Lethal dose: aprox. 0,0005 grams

Ricin is a protein that is extracted from the castor bean, it can be either a white powder or a liquid in crystalline form. It takes only about the size of half a grain of sand of this toxin for the lethal dose in humans if exposure is from injection or inhalation. The first episode on the use of this substance was in 1978, the Bulgarian dissident Georgi Markov was stabbed in the leg in public on Waterloo Bridge, London by a man using a weapon built into an umbrella. The weapon embedded a small pellet in Markov's leg which contained ricin. Markov was dead four days later.

Lethal dose: as low as 0,00015 grams

Extremely poisonous metal, especially the form of Dimethylmercury is extremely dangerous. Absorption of doses as low as 0.1 mL have been proven fatal. The toxin even passes through gloves made of latex, PVC, butyl, and neoprene and is absorbed through the skin. The toxicity of dimethylmercury was highlighted with the death of the inorganic chemist Karen Wetterhahn, just months after accidentally spilling a few drops of this compound on her latex-gloved hand.

Lethal dose: aprox. 0.00012 grams

Extremely potent toxin found in certain species of frogs, namely poison dart frogs from warm regions of Central America and South America. As a neurotoxin it affects the nervous system and kills by permanently blocking nerve signal transmission to the muscles. The toxin is released through glands located on the back and behind the ears of these frogs. When they are agitated, feel threatened, or are in pain, the toxin is reflexively released through several canals. Currently no effective antidote exists for the treatment of batrachotoxin poisoning.

Lethal dose: aprox. 0,00000015 grams

Although extremely toxic it can be used as a medication on the treatment for spastic disorders associated with injury or disease of the central nervous system including trauma, stroke, multiple sclerosis, Parkinson's disease, or cerebral palsy. Commonly known due to its use in cosmetic surgery where it can be used to prevent formation of wrinkles by paralyzing facial muscles. These medical procedures only apply a tiny portion of the toxin since it is the most acutely toxic substance known, with a median lethal dose of about 80 nanograms when introduced intravenously and 240 nanograms when inhaled. The toxin leads to paralysis that typically starts with the muscles of the face and then spreads towards the limbs followed by the breathing muscles and causes respiratory failure. This toxin is 40 million times more potent than Cyanide.