U.S. chemical weapons tests came to a halt in the early 1970s, as the 1975 Biological Weapons Convention was being negotiated. While chemical weapons were not covered, it was becoming known that chemical weapons were being tested. There was a particularly scary incident in 1968, when an open air nerve gas test at Dugway Proving Ground in Utah went wrong went winds carried the gas too far and killed a flock of sheep. Chemical weapons have always been more scary than fatal, and the government decided to shut down the testing program. Now it turns out that there were numerous chemical weapons tests in the open during the 1950s and 60s. Recently declassified records show that there were 46 tests between 1962 and 1973 that exposed 5,500 sailors and soldiers to some chemical weapons. Some 90 percent of those exposed to the weapons were sailors at sea. Another 62 planned tests were cancelled. Chemical weapons are still a contentious issue, as decades old stocks of these lethal agents are still being destroyed. The tests were necessary because little was known about the effects of the newer weapons, particularly nerve gas. In particular, it was not known what very small amounts of nerve agent (some is gas, some is liquid, in the form of tiny droplets). Wind will rapidly disperse even the droplets, and son and heat will eventually destroy the nerve agent. Or so it was thought. It is still a murky subject. Monitoring of nerve gas victims from the late 1980s (Iranians) and the 1990s (Japanese victims of terrorist attacks) continues. There are long terms effects for small doses, but no one is sure exactly what those effects are yet.