Spurred by the prominent and recurring use of pepper spray by police officers during encounters with Occupy Wall Street protesters, Deborah Blum investigated the substance and its potential health effects for Scientific American. Blum describes the Scoville scale, which measures the intensity of various peppers, placing green bell peppers at the low end and habaneros at the higher end. She notes that pepper spray, a chemically engineered substance, dwarfs the burn intensity of even the most painful peppers, and she writes about why that is:
The reason pepper-spray ends up on the Scoville chart is that – you probably guessed this - it’s literally derived from pepper chemistry, the compounds that make habaneros so much more formidable than the comparatively wimpy bells ... But we’ve taken to calling it pepper spray, I think, because that makes it sound so much more benign than it really is, like something just a grade or so above what we might mix up in a home kitchen.
She also rounds up previous studies into the long-term affects of pepper spray exposure and discovers that, as one might expect, it can be pretty dangerous:
The more worrisome effects have to do with inhalation – and by some reports, California university police officers deliberately put OC spray down protestors throats. Capsaicins inflame the airways, causing swelling and restriction. And this means that pepper sprays pose a genuine risk to people with asthma and other respiratory conditions ...
... Pepper spray use has been suspected of contributing to a number of deaths that occurred in police custody. In mid-1990s, the U.S. Department of Justice cited nearly 70 fatalities linked to pepper-spray use, following on a 1995 report compiled by the American Civil Liberties Union of California.