Deadliest substance/thing in the world by size/weight

Hello Everyone,

I was bored and started thinking what is the deadliest substance/thing that could kill a human adult that is also either very tiny. I came up with ricin, as I understand only a few grams of the stuff could be deadly, although I might be wrong. I think that was the toxin used in the spy killings when a spy stabbed someone with an umbrella tip that injected a tiny ball full of ricin.

Okay, so you get my drift. What is the smallest amount of something that can kill an adult?

Apparently you can die from swallowing as little as 50 nanograms of Polonium 210. Wiki cite.

I don’t know if this is best but Polonium is pretty toxic:

I’m sure anti-matter would be more damaging.

Edit: Ninjas are also quite deadly.

So, the answer is ninjas injecting polonium-120 using an umbrella?

Seriously, though, the amount is dependent upon the time the assailant is willing to wait for the victim to succumb.
There are bioweapons with very low dosages that will cause death in 5 days or so.

Do those count?

Does the death need to occur rapidly?

Botulinum toxin (of which Botox is one variety) might be the winner. According to Wiki:

“When introduced intravenously in monkeys, type A (Botox Cosmetic) of the toxin exhibits an LD50 of 40–56 ng, type C1 around 32 ng, type D 3200 ng, and type E 88 ng[citation needed]; these are some of the most potent neurotoxins known.”

Good point. Ultraviolet radiation can cause melanoma, so maybe the answer is sunlight.

Time. It’s weightless, yet it kills us all eventually.


According to the list here, botulinum toxin is about 10 times more toxic than polonium, and 20,000 times more toxic than ricin, but only if the latter is injected; the oral dose is a thousand times greater still, with ionizing radiation the only thing that exceeds it (what would the weight of 3-6 Gy of radiation be? Very small in any case, especially gamma rays).

Time may win on weight, but loses on size. It’s so big, it’s everywhere.

Anti-matter ninjas

Well, unless you’re Big Jim McBob and Billy Sol Hurok, the anti-matter solution has some drawbacks.

How much damage would one microgram of antimatter cause? Would it crater a fist sized hunk of flesh? Vaporize a pile of anvils? Make newspapers smolder?

One of you physics types tell me!

0.00004296 megatons.

Ebola virus perhaps? That can’t weigh much at all, and it is pretty deadly.

From wikipedia:

So, 1 microgram would produce an explosion equal to around 85 lbs of TNT.

I think this is much too high.
As my Physics prof used to say - show your work!

There are supposedly some fentynal analogues that are so insanely potent even one single grain or speck touching your skin could be fatal. For a chemist to work with it requires full bunny suit with air filter, and keep a syringe full of nalaxone handy in case your suit gets breached. Thats pretty crazy.

Humans. One of us can do a lot of damage to a large group of people while theses toxins generaly affect a single individual. At least in the quantaties above.

A vacuum.