"One of the reasons for the widespread acceptance of OC sprays is the fact that they overcome some of the problems associated with CN and CS products. Specifically, the OC sprays are effective in producing immediate blepharospasm and incapacitation of almost all subjects including those who are intoxicated or mentally ill,(32) and they are also effective against animals. Beyond these advantages, there are no known long-term toxic effects produced solely by the topical application of OC, and there are no environmental contamination problems associated with its use.(32)"

http://www.opt.pacificu.edu/ce/catalog/13541-SD/pepper.html