Actor Walter Brennan was mustard gassed in WWI, so he says, and gave him a unique vocal quality that made him rich and famous. He died in 1974 at the age of 80, almost 55 years after his encounter with the chemical. It still is a devious weapon that maimed and killed many troops during WWI.
My grandfather's autopsy revealed an enlarged heart, and most of his internal organs eaten away by mustard gas.