For more than 20,000 years, humans have used poison—in hunting, in pest and plant control, and even to kill other humans.

Castor bean residue is the source for ricin, which causes multiple organ failure. But it’s used by some indigenous tribes on their hunting arrows.

But the deadliest synthetic poison is VX, a nerve agent that stops victims' breathing. Originally developed as an insecticide, it proved too lethal for that. One gram could kill 2,500 people.

Another profoundly lethal poison is the radioactive isotope of polonium, famously used to assassinate a Russian dissident in 2006. One gram could kill 10 million people.

The most deadly one, surprisingly, is used routinely. Extremely tiny quantities of botulinum toxin, produced by bacteria, are used to paralyze facial muscles to reduce wrinkles. But just one gram could kill one billion people!

All these may be deadly, but the riskiest poisons are the ones found at home—cabinets full of pesticides, cleaning solutions and medications.

There’s one poisoning reported in the U.S. every eight seconds, and 90 percent of them occur in households.

Little kids tend to put things in their mouths, so they’re the most vulnerable. Nearly 4 percent of children below six will have a poison exposure.

A good reason to put child locks on cabinets that contain potentially poisonous household chemicals.