Mosquito Assassin: What is the most deadly substance that can be injected into someone?

Question

Designing an electronic 'mosquito' among my arsenal of 'bugs'. Some work as remote ears, others as eyes. This mosquito is the assassin. He can fly into a room and when he 'bites' someone can inject a small amount of liquid. What substance could kill a human, from immediately to 2 days after the injection.

Bonus, what substances could just incapacitate a person for at least 20 minutes?

This is Mosquito sized and as such the payload needs to reflect that. Is Ricin the most likely candidate? Can it even do this in such a small amount?

If 'spraying' the substance into eyes or mist for inhalation, that could work too!

Answer 1

Okay, I'm not sure if anyone is going to read my answer at this point, but here goes.

I don't think any of the poisons that have been suggested so far fulfill your requirements, largely due to the long time before death.

Botulinum

Botulinum is a particularly bad choice; although it has the dubious honor of having the lowest LD50 of any known substance, what it actually does is bring about a prolonged illness called Botulism, and that LD50 naturally is only relevant without significant medical intervention.

In practice, there is an antidote available, and with first world medical care (which there will be time to receive), there is actually a high chance of survival, even if a high dose is given. It's also fairly well-known and in hospitals, since people can get botulism even if they haven't been poisoned.

It may be fatal only weeks after the poisoning, if at all. One potential benefit is that it could be mistaken for a normal illness.

Polonium-210

Polonium is certain death, in the long term. It also brings about a prolonged sickness which will eventually kill, though it is expected to take 20 days, making it unsatisfactory for your purposes. There is no antidote or treatment, and hospitals are unlikely to recognize or suspect Polonium at first because of how exotic it is.

(Though in light of the publicity it has received fairly recently, they might suspect it more readily than before)

How exotic? Well, to make some Polonium, you need to have a nuclear reactor. In fact, you need to have facilities specially dedicated to producing Polonium inside that nuclear reactor. There are only a few places on Earth capable of producing Polonium at all, and almost all are located in Russia.

It's also extremely easy to trace, to the extent you can identify specific people who have handled it. If you know what you're looking for, even minute trace amounts are detectable long after you've left the scene.

Ricin

Ricin is the best candidate so far. It's almost perfect as a poison. It is relatively easy to produce (you could even prepare it in your home, though this is not recommended for obvious reasons), has no known antidote, and there is no reliable treatment whatsoever.

The only black mark against it is the time before death. The CDC says that:

Gastrointestinal effects generally occur within 6 hours of ricin exposure. Effects on the liver, central nervous system (CNS), kidneys, and adrenal glands typically occur 2 to 5 days after exposure and reflect ricin's cytotoxic effect. Patients/victims may be asymptomatic prior to the occurrence of these cytotoxic physical findings. Death may occur between 3 and 5 days after the initial exposure to ricin.

This is a lot better than botulinum and polonium, but still a little off from the mark.

If you didn't have such a high onset of death requirement, this really would be the perfect poison for any job.

VX

Although many people think VX is a "nerve gas", it isn't. It is a tasteless and odorless liquid almost exactly as a dense as water, and with the consistency of motor oil. It's more correctly referred to as a "nerve agent".

The "gas" form of VX actually refers to distribution as an aerosol, or from evaporation when an area is bombarded with liquid VX. It has a high boiling point.

Lethal Dose and Density Considerations

In mice, the intravenous LD50 is 7μg/kg, and based on human subject research, 20μg/kg should be a reliable lethal dose. For a 100 kg human, this is 2mg of VX, or 2μl in volume. According to this, mosquitos can carry between 0.001 to 0.01 ml of blood, which is slightly denser than water. As you can see, it's more than enough for this purpose.

Note that most sources for LD50 of VX for humans refer to contact LD50, which is significantly higher. It also takes a lot longer to take effect.

Time before death

In general, inhalation or intravenous VX can reach peak toxicological effects within minutes. After this point, the time before death depends on the dosage. With a sufficiently high dose, death can occur within 10 minutes to a few hours.

Survival

Although antidotes to VX exist, intravenous VX works too quickly for antidotes to be useful, unless they are immediately available. However, as VX poisoning has identical symptoms and treatment to other nerve agents, including more commonly available insecticides, it isn't unknown in hospitals. Tests for nerve agents are standard when poison is suspected.

Availability

VX is considered a weapon of mass destruction, and is recognized as the single most potent chemical warfare agent ever produced. It is not easy to produce, especially in pure form, and many of its precursors are also illegal and controlled, though none require a nuclear reactor and a team of physicists. However, considering the thousands of tons of this substance that have been produced to date by governments and subsequently destroyed, it isn't unlikely some of it has escaped into the black market.

Further Reading:

1. Molecules of Death, Waring, Stenton, Mitchell
2. Chemical Warfare Agents, Romano, Lukey, Salem
3. Chemical Warfare Agents, Marrs, Maynard, Sidell
4. Death by Polonium-210

Answer 2

If you have something the size of a mosquito, then you are, naturally, limited by the payload that a mosquito can carry. A mosquito has a total mass of roughly 1-2 milligrams. The median lethal dose (MLD) of Ricin, injected, to a human is 22 micrograms per kilogram of human. So, a lethal dose of Ricin for an average human would require 1.78 milligrams. Your electronic mosquito would need to be rather large to carry around this much.

However, Ricin is FAR from the most lethal substance to humans. Reading a quick list online showed at least 7 compounds that are lethal in smaller doses than Ricin. At the very top of the list is Botulinum Toxin. Botulinum Toxin is the most spectacularly lethal neurotoxin we have ever encountered...it has an estimated Median Lethal Dose of merely 1.3-2.1 nanograms per kilogram. Mass of an average person is 62 kilograms, so a lethal dose of Botulinum Toxin is only 130.2 nanograms. Or, for more clarity, 0.0000001302 grams. This is certainly small enough to be delivered by a mosquito-sized deliver system, and could easily be delivered in a much higher dose.

For a bit of clarification...median lethal dose represents the amount necessary to kill 50% of the test targets. So you are going to want to up the dosage of this toxin to make sure you get everyone...but since the amount delivered is measured in nanograms, this isn't a problem for your delivery method. The problem is that while botulinum toxin is spectacularly lethal, it doesn't do so quickly when administered in a 'lethal dose.' It takes several days before the symptoms become fatal, and there are effective anti-toxins against it.

Polonium-210 is another option for you (It has a similar MLD), if you want to kill them with radiation poisoning instead of neurotoxin...but again, it's slow. Probably not within two days if you stick to the actual MLD levels

It's simply a matter of volume...there are too many neural cells for a tiny amount of poison to tear up quickly. There is a way to speed things up, and that is to have your mosquito precision-target where it delivers the poison. Delivering the poison as close to the spinal cord and brainstem as possible. So if you want this to work quickly, you need to massively overdose them on it.

So, how much could a mosquito deliver? A mosquito that eats until it is full can harvest 0.01 milliliters of water. As 1 milliliter of water weighs 1 gram, we can compute that a mosquito can carry an additional 0.01 grams of matter and still fly well. Remembering that the MLD of botulinum toxin is 130.2 nanograms, we can compute that a single mosquito could carry 7,680,915.5 times the MLD of botulinum toxin.

That'll do it. Botulinum Toxin is definitely the way to go in this case.

Answer 3

Liquid Antimatter injection

You have electronic mosquitoes, and these mosquitoes can carry liquid antimatter. A 10 trillionth of a gram of positrons (anti-electron), has slightly more destructive power than a hand grenade, so if you inject liquid antimatter into the person you'd probably get a much larger explosion. Kill 100% of targets.

Liquid antimatter can be suspended using maglev.

Once the mosquitoes land on target, inject the positron(s) into them and watch them go kaboom.

You never said I couldn't explode them (actually, you didn't say that it has to be poison either)...

Answer 4

Botulinum neurotoxins.

The LD50 (dose that will kill 50% of exposed specimens) of some types is 1.3–2.1 ng/kg. For an 80 kg human you need 104-168 nanograms, a new type only requires 2 nanograms to kill. It's one of those most poisonous substances known. The best part is that the mosquito can simply house some Clostridium bacteria in its "gut". With those bacteria, the mosquito can wait and produce more botulinum if it runs out. A strong dose will cause paralysis of the breathing muscles, leading to a relatively quick and subjectively terrifying death (and they're unable to scream). Smaller doses can be used to kill more slowly.

Just make sure to get the correct type. Type A is used as the cosmetic procedure known as Botox. While and, as yet unnamed type, can kill with an injection of 2 billionths of a gram or inhalation of 13 billionths of a gram.

Answer 5

Active agents instead of pre-made poisons

Such a delivery method can be used to infect the host with various horrible diseases, designed to make them die in an arbitrary manner of your choice - in essence, instead of delivering a tiny amount of some toxin, you can deliver a virus or bacteria that will multiply and manufacture a large amount of it.

The hard parts in weaponizing diseases seem to be (a) an efficient delivery vector, which in your case doesn't need to be included "in" the disease and (b) having the disease be not too deadly so it gets a chance to spread before the victim dies or gets isolated. In this scenario, it'll be enough to make a disease strain that is horrible at spreading and will multiply only in perfect conditions such as your bloodstream.

Answer 6

Perhaps I'm oversimplifying here, but why not have the mosquito as a simple air pump and just pull from the atmosphere and inject an air bubble?

An air bubble in the body is called an air embolism and can have a huge variety of impacts, depending on where it ends up. This is probably something that the mosquito can target to get a specific effect - ranging from disorientation/ paralysis of legs right through to near instant death.

https://skeptics.stackexchange.com/questions/17194/can-an-air-bubble-in-a-syringe-kill-the-patient has a very in depth explanation of how air can kill someone.

In 1949 New Hampshire physician Hermann Sander ended the life of a terminal cancer patient by injecting her with 40 milliliters of air — four syringes of 10 milliliters each.
(Source according to http://www.straightdope.com/columns/read/2866/can-air-injected-into-the-bloodstream-really-kill-you)

Answer 7

An interesting method of killing someone using a mosquito sized robot would be to inject liquid Hydrogen into their bloodstream. Once in the blood, 1 milligram of liquid Hydrogen would become a 25ml gas embolism.

5mg of liquid Hydrogen, injected into the right spot could render any number of effects, including death. This method is very similar to the air injection method, except the liquid hydrogen could be injected a whole lot faster by a mosquito robot, increasing the effectiveness of the embolism.

SCIENCE FICTION ANSWER:

Give the mosquito robot a coil of Monofilament (Monomolecular wire). Instead of a liquid poison. The robot would insert the monofilament into one of the targets veins and the blood flow would draw monofilament into the circulatory system. In a matter of minutes, it would slice through all of the curved blood vessels and internal organs, including the heart. Not a death I would wish on anyone.

Answer 8

Come up with a chemical catalyst that induces proteins to fall apart in shorter molecules.
Just about everything critical in the body is protein based.
Get only a tiny amount of such a catalyst in the blood-stream and the victim is guaranteed to be dead in a few hours.
The neat thing about a catalyst is, that it isn't consumed in the reaction, so it just keeps flowing through the body with the blood and destroys protein left and right.
And, unless the existence of such a weaponized catalyst is expected, nobody will have any clue what killed the victim. (A new Ebola strain, Marburg, flesh eating bacteria ? It's going to take a while to figure that out...)

The remains of the victim will even be a major bio-hazard to any other form of life that has direct contact with it.
The ambulance personnel that takes him to the hospital, the doctors and nurses, the coroner examining the remains...
It more or less acts like Ebola, but is even more dangerous, because it infects others through any direct contact, not just transfer of bodily fluids.

Answer 9

Chlorine Trifloride. Make your mosquito right, and you might get a flying bomb...

Chlorine Trifloride is extremely reactive with most inorganic and organic materials, including glass and teflon, and will initiate the combustion of many otherwise non-flammable materials without any ignition source. These reactions are often violent, and in some cases explosive.

Vessels made from steel, copper or nickel resist the attack of the material due to formation of a thin layer of insoluble metal fluoride, but molybdenum, tungsten and titanium form volatile fluorides.

The ability to surpass the oxidizing ability of oxygen leads to extreme corrosivity against oxide-containing materials often thought as incombustible. Chlorine trifluoride and gases like it have been reported to ignite sand, asbestos, and other highly fire-retardant materials. Fire control/suppression is incapable of suppressing this oxidation.[14] The compound reacts violently with water-based suppressors, and oxidizes in the absence of atmospheric oxygen, rendering atmosphere-displacement suppressors such as CO2 and halon completely ineffective. It ignites glass on contact.

Exposure of larger amounts of chlorine trifluoride, as a liquid or as a gas, ignites tissue. The hydrolysis reaction with water is violent and exposure results in a thermal burn. The products of hydrolysis are mainly hydrofluoric acid and hydrochloric acid, usually released as steam or vapor due to the highly exothermic nature of the reaction. Hydrofluoric acid is corrosive to human tissue, is absorbed through skin, selectively attacks bone, interferes with nerve function, and causes often-fatal fluorine poisoning. Hydrochloric acid is secondary in its danger to living organisms, but is several times more corrosive to most inorganic materials than hydrofluoric acid.

Answer 10

Georgi Markov was killed by bulgarian government agents using a weaponized umbrella.

Agents of the Bulgarian secret police (Darzhavna Sigurnost; Bulgarian: Държавна сигурност, abbreviated ДС), assisted by the KGB, had previously made two failed attempts to kill Markov before a third attempt succeeded. On 7 September 1978 (the 67th birthday of Todor Zhivkov), Markov walked across Waterloo Bridge spanning the River Thames, and waited at a bus stop to take a bus to his job at the BBC. He felt a slight sharp pain, as a bug bite or sting, on the back of his right thigh. He looked behind him and saw a man picking up an umbrella off the ground. The man hurriedly crossed to the other side of the street and got in a taxi which then drove away. The event is recalled as the "Umbrella Murder" with the assassin claimed to be Francesco Gullino, codenamed "Piccadilly".[3]

When he arrived at work at the BBC World Service offices, Markov noticed a small red pimple had formed at the site of the sting he had felt earlier and the pain had not lessened or stopped. He told at least one of his colleagues at the BBC about this incident. That evening he developed a fever and was admitted to St James' Hospital in Balham, where he died four days later, on 11 September 1978, at the age of 49. The cause of death was poisoning from a ricin-filled pellet.[4][5][6]

The mechanism was a small pellet with holes, containing ricin that was projected via pneumatic means.

So, here you have your killer mosquito.

Wikipedia article

Answer 11

Burn them to death

A quick trip to the Scoville Heat Scale shows that there are some incredibly hot chemicals, chief of which is the resiniferatoxin rated at 16 billion Scoville heat units. The humble jalapeno is a mere 1000 to 4000 heat units.

The LD50 oral dosage in rats for resiniferatoxin is 148mg/kg from this Materials Safety Data Sheet. (The MSDS doesn't list LD50 values for resiniferatoxin as an inhalant or by injection, so it's guess work on what those would do. Also, these values are higher than the LD50 values for oral capsaicin. Weird.) While these values don't come anywhere near the lethality of botulinum toxin, consider the effects of having pure chemical hellfire injected into your veins.

This answer is more along the lines of "Holy **** that must hurt so bad! If you weren't dead, you wish that you were."

Answer 12

Nanomachines

You've already got tiny insects as eyes and ears, why not even more tiny insects as assassins? The "mosquito" can land on someone, and then inject a swarm of nanobots that gather in sensitive areas to await the "kill" command being sent by their controller.

Failing that, how about Unobtanium? You never specified that it had to be a substance that exists in the real world, and unless you're trying to write a really true to life crime thriller, why would it need to? Just make something up, and pretend it always existed. Authors do this all the time. There's nothing to say that an alternate world with the technology to invent mosquito assassins doesn't also have the technology to invent or discover new poisons, and in fact it would be surprising if they didn't.

Answer 13

Technitium-99M

I hope someone can double-check my calculations here.

First, it's radioactivity: http://www.iem-inc.com/information/tools/specific-activities

5,200,000 Curies per gram. Based on some of the other answers above I'll figure a 1 milligram payload, thus 5,200 curies of Tc-99M

Now, to convert that to a dose: http://www.drugs.com/pro/technetium-tc-99m-pentetate.html

A 20 millicurie injection of Tc-99M gives about .6 rem. Thus our 1mg dose is 156,000 rem. A prompt radiation kill only needs about 5,000 rem, this means our material only needs to be 3% Tc-99M to meet your requirements--it can be mixed with something to make it more injectable.

You could accomplish the same thing with Po-210 by using a larger dose (still well within the capacity of the e-mosquito) than was discussed above but it still has the problem of limited sources. Tc-99M, however, has many more sources due to the need for local production for medical procedures.

Answer 14

This is the worst acid thing known. it really does eat everything

Hydrofluoroantimonic acid

Fluoroantimonic acid (systematically named fluoranium hexafluorostibanuide and fluoranium hexafluoridoantimonate(1−)) is an inorganic compound with the chemical formula H2FSbF6 (also written H2F[SbF6], 2HF·SbF5, or simply HF-SbF5). It is an ionic liquid created by reacting hydrogen fluoride (HF) with antimony pentafluoride (SbF5) in a stoichiometric ratio of 2:1. It is the strongest known superacid, which has been demonstrated to protonate even hydrocarbons to afford carbocations and H2.1 Similar acids can be created by using excess antimony pentafluoride.

Answer 15

The thing that makes today's mosquitos the most deadly animals is mentioned, but never extrapolated: disease. The 0.01ml (= 10E-8 m³)of mosquito payload would mean about 10E14 virus particles (each measuring 10E-23 m³) - this is slightly above the number of flu-virus particles found in people at the peak of a flu - could fit with some fluid surrounds to make them injectable.

Viral Meningitis would fit the bill in terms of payload and rapid death, for more spectacular forms of death Ebola would be a go-to, but it would need to be modified to act faster to fit your bill. Note that with viral actors the damage done to the cells is the crippling feature of the disease (unlike some bacterial infections where a by-product of the bacterium may act as a poison), and this is only achievable by the virus particle infecting cells, so there is a lower bound to the reaction time. Still, many cells induce apoptosis (a sort of cellular suicide completed in less than 1 hour) as soon as viral infection is detected, on the sound evolutionary reasoning that the organism might survive if the cell is not enabling the virus to multiply; This will work in our favor here, as the viral load will be immense from the get-go.

A mixture of viruses, some targeting the immune system itself, and some antigenes in the mix that nullify the immune system's first wave response of antibodies, would make that a wrap.