Trichothecenes: from Yellow Rain to Green Wheat

M ore than 20 years ago, trichothecene mycotoxins made their controversial debut on the world stage. Alexander Haig, who was U.S. Secretary of State and visiting the western sector of then-divided Berlin, alleged in 1981 that trichothecenes had been used as biological warfare agents in Southeast Asia. He cited statements from villagers in the region, who claimed that they became ill after “yellow rain” fell from the sky. Subsequent chemical and biological tests on samples that were smuggled by soldiers and refugees from Laos and Cambodia to Thailand and brought to the United States for analysis indicated several trichothecenes were present within some of the samples, including T-2 toxin, deoxynivalenol (DON), and nivalenol (NIV). However, although many species of the genus Fusarium produce such chemicals, biological analysis showed that the yellow spots on some samples contained high amounts of pollen and were likely deposited by Asian honeybees. On the basis of such findings, Matthew Meselson of Harvard University in Cambridge, Mass., and his colleagues concluded that the trichothecenes contained in those smuggled samples derived from natural sources and not from biowarfare agents. During the past 20 years, individuals from several additional nations, including Afghanistan and northern Iraq, have alleged that trichothecenes were being used in biological weapons. Although proof for those allegations is scarce, officials with the United Nations Special Commission on Iraq (UNSCOM) obtained confirmation during the early 1990s after the Persian Gulf War from the Iraqi government of its biological weapons program, which included trichothecene production. According to UNSCOM documents, a team of Iraqi microbiologists began research on large-scale fermentation and purification of trichothecenes for weapons development around 1987. UNSCOM officials further concluded that there was no evidence that Iraq used trichothecenes or other mycotoxins as weapons.