Comparative acute toxicity of o-chlorobenzylidene malononitrile (CS) and oleoresin capsicum (OC) in awake rats

Tear gases are largely used to control civil unrest. Their incapaciting effects involve eyes, skin and respiratory tract. This study was performed to compare acute respiratory effects of o-chlorobenzylidene malononitrile (CS), oleoresin capsicum (OC) and their respective solvents in awake rats, using an integrated system of nose-only exposure and multiple monitoring of breathing. Aerosols were generated by a Collison Nebulizer from the solutions held in tear gas sprays. The reduction of minute ventilation, observed during a 5 min exposure, was significantly more important with CS than with OC: minute ventilation represented 29 +/- 8 and 50 +/- 6% of preexposure minute ventilation respectively (P < 0.05). The reduction of minute ventilation observed with CS and OC solvents alone was not significantly different from that observed with the tear gases themselves. The decrease in minute ventilation observed, between the second and the fifth minute of exposure, was of the same level for repeated exposure separated by 24 h, Time necessary to recover to 80% of pre-exposure minute ventilation was not significantly different between the two tear gases: 722 +/- 272 and 691 +/- 262 s for CS and OC respectively (NS). Histological analysis of the trachea, performed at the end of exposures, revealed an increase in mucus secretion after exposure to OC and cytoplasmic vacuoles in epithelial cells after exposure to CS, In the lungs, interstitial oedema was observed after exposure to OC and emphysema after exposure to CS.