I haven't thoroughly read through all of this yet, just taken a basic look at it. Biological warfare against North Korea is an issue that is often raised but generally treated as "inconclusive".

Twitter thread plus summary and scans: https://threadreaderapp.com/thread/1562557442386300941.html

PDF of report: https://s3.documentcloud.org/documents/22187637/china-peoples-commision-report-on-bw-apr-1952.pdf

This kind of historical material was withheld from American people by a huge USPS/Customs Service/FBI program to destroy publications from Communist countries during the Cold War. Now you can read for yourself & make up your own minds.

When it comes to documents from the period of the Korean War, most Americans are totally unaware that during the 1950s and first half of the 1960s, the U.S. government “engaged in wholesale confiscation of publications mailed into this country” from Communist countries. This meant any materials emanating from North Korea, China, the Soviet Union or other allied countries (such as those in East Europe at that time) were intercepted and destroyed by U.S. postal officials.

Medium article about the postal service destruction of publications: https://jeff-kaye.medium.com/censored-north-korea-accused-u-s-of-working-with-unit-731-war-criminals-on-bw-attacks-d7fd819ed8b7