In 1988, around 5,000 Kurds died at Halahbja after Iraq used both sarin and sulfur mustard. Sarin further became a household name after the 1995 Tokyo subway attack in which the religious cult Aum Shinrykio used sarin to kill 12 people and harm thousands more.

So, what does sarin do to our bodies?

Effect of sarin on the left eye of a rabbit (pupil constriction) [ Effect of sarin on the left eye of a rabbit (pupil constriction) [ Journal of Medical, Chemical, Biological, and Radiological Defense

Sarin is unique in potency but not in mechanism. There are other drugs, pesticides, and plants that work the same way. They are called cholinesterase inhibitors.

Our nerves talk to each other by releasing chemicals called neurotransmitters. The amount of a particular neurotransmitter helps determine whether a nerve fires or not. What so-called nerve agents do is alter those neurotransmitters. They kink the signaling between our nerves, telling them to do things they normally do, but with altered frequency.

After a neurotransmitter has done its job, delivered its message, an enzyme usually comes along and demolishes it. But nerve agents block those enzymes. The enzyme can't break down the neurotransmitter, so the neurotransmitter stays around and keeps giving its message. If that message was, say, to release a little water onto your eye because your eye was dry, now the repeated message becomes "make your eyes water uncontrollably."

Here is a drawing of that reaction, just like in organic chemistry class (still a requisite for all U.S. doctors). The big block is the enzyme (acetylcholinesterase). In the top image, it's working normally: breaking down the neurotransmitter (acetylcholine) into smaller parts. In the bottom images you can see how the "nerve agent" (sarin in our case) just kind of hangs out in the "esteric site," so then the enzyme cannot do its job.

The action seems pretty benign on paper. But as acetylcholine builds up in our bodies, we become extremely uncomfortable and die. We are killed by the accumulation of our own normal neurotransmitter telling our own nerves to do the normal things they normally do, just in excess. One could draw an analogy to cancer. In this case, though, neurotransmitters live and die on an order of milliseconds, so it happens in a flash.

Within seconds of exposure to sarin gas (or liquid, which evaporates easily), we start to notice the immediate effects of acetylcholine buildup. First, our smooth muscles and secretions go crazy. The nerves to those areas keep firing, keep telling them to go. The nose runs, the eyes cry, the mouth drools and vomits, and bowels and bladder evacuate themselves. It is not a dignified state.

Since sarin has no smell or taste, the person may very well have no idea what's going on. Their chest tightens, vision blurs. If the exposure was great enough, that can progress to convulsions, paralysis, and death within 1 to 10 minutes.