The Us dumped over 212 tons of nerve agents from 1969 to 1970.
n fiscal year 2008, the U.S. Department of Defense released a study finding that the United States had dumped at least 112 tonnes (124 short tons) of VX into the Atlantic Ocean off the coasts of New York/New Jersey and Florida between 1969 and 1970. This material consisted of nearly 22,000 M55 rockets, 19 bulk containers holding 640 kg (1,400 lb) each, and one M23 chemical landmine.[42].
https://en.wikipedia.org/wiki/VX_(nerve_agent)