What Is the Most Poisonous Chemical Compound?

When you get right down to it, everything is poisonous. Water will kill you if you drink too much of it. Oxygen is a deadly poison, yet we need it to live. However, there are some chemicals that we are better off not encountering. Here's a list of the most poisonous chemicals known. Keep in mind, toxicity varies from one species to another (i.e., what may be poisonous for a mouse may be more/less poisonous to a human) and within a species (i.e., age, sex, genetics all affect susceptibility to a toxin). I've listed the name of the toxin, its source, approximate average lethal dose per kilogram of body weight (LD50), and the species.

1. tetanus
1 nanogram/kg
mouse, human

2. botulinal neurotoxin (bacteria)
1 nanogram/kg
mouse, human

3. shigella (bacteria)
1 nanogram/kg
monkey, human

4. palytoxin (coral)
60 nanogram/kg
dog (iv)

5. diphtheria (bacteria)
100 nanogram/kg
human

6. ricin (from castor beans)
1 microgram/kg
human

7. aflatoxins (mold which grows on nuts, legumes, seeds)
1-784 micrograms, depending on type of aflatoxin
duckling (oral)

8. shigella (bacteria)
1 microgram/kg
mouse

9. saxitoxin (shellfish)
3-5 micrograms
mouse (iv), about 50x higher dose orally

10. tetrodotoxin (fugu pufferfish)
10 micrograms
mouse (ip)

11. diphtheria (bacteria)
1.6 milligram/kg
mouse

Sources:

Merck Index, 11th Ed., S. Budavari et al. (editors), Merck (1989) ISBN 911910-28-X

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