Is climbing chalk toxic?
Unadulterated climbing chalk is magnesium carbonate, MgCO3, a chemical once sold out of pharmacies for oral application to plunge stubborn stools and quelch indigestion. Even today, magnesium carbonate can be an ingredient in antacids and is used as a food additive. When you eat chalk, it causes your intestines to absorb water, and, well, the rest isn’t pretty. Think of it as a poor man’s Ex-lax. Eating chalk isn’t going to harm you, but it can literally have you crapping yourself over that big unclimbed block you found deep in the woods.
Magnesium carbonate is not a known carcinogen, and is given a “slight” hazard rating by various government organizations, although the effects of long-term exposure are unknown. According to the U.S. Department of Labor, magnesium carbonate can be a skin and respiratory irritant, but isn’t considered toxic. Breathing clouds of chalk, such as inside a poorly ventilated gym could cause you to cough and wheeze, and you might experience some tightness in your chest. The discomfort will be like having Jenna Jameson step over you as you lay semiconscious on the floor after pitching off the black problem with red stripes (with sit-knuckle start!). Getting fresh air will clear you up in no time.
All of the above is relevant to pure chalk only. Note that various climbing chalks might contain additional drying agents and even scents that are carefully engineered to keep you from having to shower every week. I can’t vouch for the safety of chalk additives, but they wouldn’t sell that stuff if it could kill you, right? I’ve found that some of the blends do cause my skin to crack, and I’ve had better results with pure, uncut MgCO3, which you can buy for 60 cents a block straight from the man himself at www.frankendo.com. Now, here’s a little trick that’s worth the price of the magazine alone: Next time you chalk up, blow on your fingers before you grip the rock. This may look Froggy, but the blowing off of residual chalk will leave your fingers with just the perfect amount, and the molecules of spit on your fingers will actually improve your grip. Don’t believe me, just ask Tommy Caldwell.