The heavy reliance on tear gas, pepper spray, and other "safe" crowd control measures from Oakland to Cairo is raising new concerns about just how much damage police and armies are doing to unarmed citizens. Weapons like these are intended to protect crowds from more dangerous shows of force like guns and batons, but even when used correctly (which is not always the case) they may be doing permanent damage to the people they're used on.

Doctors in Egypt are saying that the tear gas used in Tahrir Square in recent days is particularly toxic and may have actually caused the deaths of some protesters. A man working at field clinic in the square says, "About 70 per cent of the injuries are fainting. People are coming in with asthma, convulsions sometimes - this wasn't often before." Some of the 30+ people killed in the last week are believed to have died from asphyxiation.

Protesters at UC-Davis who were shot in the faces with pepper spray last weekend complained of pain and irritation in their breathing passages even days after their arrests, and a pregnant woman sprayed at Occupy Seattle says she suffered a miscarriage as a result. (That claim hasn't been verified, and The Stranger says her story is "increasingly dubious.")

Some of the other "non-lethal" methods that are popular among police and armies.

Rubber bullets: Like real bullets, these are fired from guns, via aluminum cartridges, and though they may not penetrate the skin or explode, can still cause tremendous pain and injuries. Several years ago, a woman in Boston was killed after being struck in the head by a rubber bullet while celebrating a Red Sox World Series.

Sound weapons: The NYPD has been seen brandishing a Long Range Acoustic Device, or "sound cannon" that can target a loud piercing sound directly at large crowds. The devices are meant to disorient and confuse, but can cause permanent hearing loss if people get to close. 

Stun guns: Used for subduing individuals rather than crowds, there have been numerous instances of people dying after being shocked with these extremely painful weapons.

It's true that these options make police less likely to use their real guns on otherwise unarmed suspects. However, giving security forces a violent, non-lethal option may make them more likely to escalate to that option immediately, rather than exhausting more peaceful solutions first. That's not even addressing the fact that it doesn't do well for international relations to have protesters in foreign countries brandishing spent canisters that say "Made in the USA" (complete with addresses and fax numbers of the manufacturer.) While crowd control is an important and necessary function of any police unit, it may be time to rethink the methods and tools used to accomplish it.