Tôn Thất Tùng was a key player in the effort to counter environmental warfare. In July 1951, he traveled to China and North Korea. Upon arrived in Peking (Beijing) on 28 July, he proceeded to carry out both political and medical exchanges. Tùng next visited the Democratic Republic of Korea. In August 1951, the fighting on the Korean peninsula was intense and Tùng witnessed the regular bombings of Pyongyang. He noted in his diary how the residents of Pyongyang had come to know the schedule of what he called 'American' bombs. Tùng's observations of life in North Korea were eerily similar to later accounts of life in Hanoi during the US bombings of the 1960s. Tùng left at the end of 1951 before the charges of US germ warfare and his training as a surgeon would not have shed much light on biological weapons. He did, however, serve as the chair at the first meeting of the Committee to Prevent Germs (Ban Chống Trùng or BCT) held from September 12 through 16, 1952.

In addition to serving as the chair of the first meeting of the BCT, he served as the president of the planning group assembled after the third meeting of the committee. Among other things, this group laid out three guiding principles to deal with biological weapons. These were:

1. The response to natural disasters should be used as a basis for the response to combatting enemy-inflicted destruction;
2. The Masses (i.e. the People) should be the basis of response;
3. There are two kinds of hygiene: short-term campaigns and everyday, regular practices. The short term campaigns are useful to establish regular practices and the regular practices are a continuation of limited-time campaigns.

This alleged use of biological warfare in the early 1950s by the Americans and French in Korea and Vietnam helped frame the subsequent use of chemical herbicides, including Agent Orange, by the American and South Vietnamese militaries from 1961 to 1970. By that time Tùng had largely stopped his surgery practice but he continued an active research program into the possible effects of herbicides on present and future generations of North Vietnamese.