On the first Earth Day angry students wore gas masks to protest the quality of the air they were breathing. That was an option not available to those who first encountered chemical warfare. In 1915, clouds of chlorine gas drifted through the trenches in Belgium, blinding and asphyxiating their victims. Modern versions are much more efficient. A pinhead-size drop of nerve agent can induce convulsions, loss of muscular control, and certain death through paralysis of the lungs and other organs.
Chemical weapons are also treacherous to make, keep and dispose of.
In 1990, millions of dead fish washed up on nearly 40 miles of shoreline in the former Soviet Union. Suspicions settled first on a possible radiation leak from an aging nuclear submarine. U.S. chemical weapons are stored at eight locations across the continental United States and on Johnston Island, about 700 miles south and west of Hawaii. At some of those sites a number of M55 rockets, loaded with nerve agent, have been leaking a vapor. There's no conclusive evidence of the cause, but one theory is that the stabilizer in the fuel is deteriorating, which could increase the risk of accidental ignition.