In 1972 it was advised that a known impurity precluded the use of these herbicides in Vietnam and all remaining stocks should be returned home. In 1977 the United States Air Force destroyed its stocks of Agent Orange 200 miles west of Johnston Island on the incinerator ship M/T Vulcanus. The impurity, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was a suspected carcinogen that may have affected the health of over 17,000 United States servicemen, 4,000 Australians, 1,700 New Zealanders, Koreans, countless Vietnamese soldiers and civilians, and with over 40,000 children of veterans possibly suffering birth defects from herbicidal warfare.