There's a vested interest between the corporations that manufacture them, the governments who sanction their use, and the law enforcement officers trying to manage a public image while also maintaining control - the combination of those things together leads to a kind of covering up for the medical effects of tear gas and other riot control technologies.

Writer Anna Feigenbaum explores a century of tear gas in use at home and abroad - as a tool of public torture developed largely in secret, as a capitalist product applied liberally to labor and political demonstrations, and as the only solution the ruling class offers to those protesting the poisoned world they've built.

Anna is author of Tear Gas: From the Battlefields of WWI to the Streets of Today from Verso Books.

Download a guide to riot control weapons from the civic media group #riotid