Two years ago, former Secretary of State Alexander Haig publicly accused the Soviet Union of conducting chemical warfare by proxy in Afghanistan and Southeast Asia. According to the State Department, the Soviet Union was manufacturing substances with the highly toxic chemical tricothecene mycotoxin and selling it to its allies for use against "resistance fighters" in those areas of the world. In addition, the U.S. government has reports from members of the Hmong tribe in Laos who claim to have seen this chemical dropped in the form of "yellow rain" from airplanes. If these charges are correct, the Soviet Union would be in violation of two international treaties, made in 1925 and 1972. Last spring, Matthew S. Meselson, Cabot Professor of Natural Sciences, challenged the State Department's evidence and conclusions, claiming yellow rain to be merely bee excrement.

The Crimson conducted a discussion last week with Meselson, Peter Ashton, Arnold Professor of Botany, and Stuart Schwartzstein, director of the Chemical/Biology Weapons Information project with the Institute for Foreign Policy Analysis the Fletcher School of Law and Diplomacy, Crimson editor Lavea Brachman moderated the discussion.

Crimson: Does the U.S. State Department, have sufficient proof, either scientifically or from sources in Southeast Asia, to prove the existence of yellow rain?

Schwartzstein: The short answer to that is, it depends on how you view the evidence. To lengthen that slightly, it depends on what access you have to the evidence at the State Department and other agencies of the U.S. government.

Ashton: I'd go back and ask what is meant by "yellow rain," because one of the problems is a question of definition.

Schwartzstein: Let's get back to the larger question. To be properly certain. I think you'd have to ask several different questions. First of all, can one draw the conclusion that chemical warfare has been waged in southeast Asia? If so, can one identify substances? And, as part of that, can one accept the State Department conclusion that among those substances that have been used are mycotoxins? I think the problem of the use of the term yellow rain is it's become almost a generic term for chemical warfare. It's been popularized. I use it to mean a popular term that designates a general chemical warfare, but I prefer not to use the term yellow rain actually.

Meselson: I would use it to mean the alleged agent of toxic warfare in Southeast Asia. The test of a good definition is whether it applies consistently to something out in the real world. In this case there is such a test. It is this: There have been sixteen cases of which I'm aware where people have brought samples of something to embassy officials--the U.S. embassy, the Canadian embassy, the Australian embassy--or Thai government officials, United Nations officials, British officials. Every one, with no exception, turned out to be pollen, but people alleged that this was an agent of warfare, so it fits the definition. What we've done is to prove essentially that yellow rain is not an agent of war, that it is bee feces. The army's view, the last time they enunciated a view, was that the yellow rain does contain pollen. They say it's because the Communists collect pollen that has been gathered by insects previously, and face it with toxin. What we think we have done is to rule out that hypothesis and to produce convincing evidence that what this stuff is, is the dropping of insects. The State Department has made a colossal error.

Crimson: So, in response to my question, does the State Department have enough evidence to prove the existence of this substances?

Meselson: Exactly the contrary. The State Department's own evidence contradicts their conclusion. They have inadequately considered their own evidence. Evidence now available to the State Department points in precisely the opposite direction.

Schwartzstein: I would take issue with that. First of all, there have been enough reports from individuals who come from Laos and Cambodia. The reports of use go back to about 1976, but it wasn't until 1981 that the State Department released any literature at all. There's been a lot of sample testing between those years and it all turned out negative. When, in the summer of 1981, the samples were run through and tested for the presence of mycotoxins, it came out positive. The feeling was that there was the explanation.

Meselson: I disagree. The people I know who have conducted extensive interviews in the Hmong camp have told me that they're really not sure whether there is any chemical warfare--that they're impressed by the stories--but that there are also inconsistencies. I don't think it is right to say that everybody who has talked to the Hmong believe in the existence of yellow rain.

Schwartzstein: Oh I didn't say everyone, but there's a feeling that the Hmong are accurately reporting their observations.

Meselson: I must disagree with that, because it is the Hmong who handed in the samples and said "this is what comes from the airplanes." Some of these absolutely do not come from planes. They are bee feces. So when someone presents you with a yellow material and says "this came out of an airplane or out of a weapon,"--bee feces don't come out of airplanes or weapons--and you know that he's wrong about that, that should tell you that everything else he has said needs to be reevaluated.

Crimson: Would you then say that the Hmong have been put up to this?

Meselson: That I can't say. I know only the things that we can establish by objective, scientific criteria here. I have no reason to believe that they've been put up to anything. But there's just no way around it, bee feces cannot, do not, and never come out of airplanes.