The Egyptian military and police are using tear gas that could cause acute damage to the lungs, liver and heart, and increase the risk of miscarriage, Egyptian media report. Apart from the detrimental side effects, the gas canisters were at least five years past the expiry date.

The news site Bikyamasr says demonstrators were exposed to dangerous levels of CR gas over the past two days of protests, with many calling the use of gas a crime against humanity. Protesters who were exposed to high doses of CR gas reportedly coughed and vomited blood and many were taken to medical care after they passed out.

Popularly known as CR gas, this incapacitating agent was developed by the British Ministry of Defense as a riot control measure in the 1960s and its effects are six to 10 times more powerful than those of the widely used CS gas. CR gas is suspected to be carcinogenic and can even be lethal when administered in a poorly ventilated space. The gas can melt human skin if it comes in contact with sweat.

Contrary to its name, CR gas is solid at room temperature with pepper-like odor. It is not utilized for riot control in the U.S. because of its alleged carcinogenic properties. The U.S. military classification for this chemical agent is combat class chemical weapon causing serious side effects for humans.

CR gas was listed as a restricted substance during the Paris Convention on Chemical Warfare of 1993, and was eventually banned, due to its toxicity.