------NAllJRE VOL..l03 s MAY 1983 NEWS------South-East Asian toxins after it falls on vegetation, wind-borne pollen adheres to the spot. • Pollen is used in the manufacture of the toxins, either as growth medium for the Is yellow rain simply bees' fungi or - as the State Department has suggested- to provide a carrier for the toxin that could be readily inhaled. natural excreta? • Pollen was mixed into the substance Washington Nowicke, a palynologist at the Smithso­ sprayed in the Thailand "attack" as a THE startling suggestion that "yellow nian Institution who has looked at several diversionary tactic to confuse Western rain" may simply be the excrement of bees of the samples, the spots contain pollen investigators. was put forward at a meeting last week in from many different families of plants. The Boston discussions, while on the one Boston, Massachusetts. The discovery of "It's hard to imagine that any one bee hand adding to the long list of questions large quantities of pollen in yellow spots would collect this tremendous diversity of about yellow rain, may also have dashed found on leaves in Thailand (see 17 pollen", she said. early hopes that the discovery of pollen in March, p.200) had already prompted Another puzzle, according to Dr H. the samples might help to provide some speculation that the yellow rain - said by Bruno Schiefer of the University of Saskat­ answers. Nowicke explained that since it is the US State Department to be evidence of chewan, is why, if it is a natural occurrence, often difficult to identify a pollen grain's Soviet use of toxin weapons - may in fact it has only been reported in the past two family, let alone its species, it is virtually be of natural origin. years. Similarly, he questioned why there impossible to determine whether the pollen The idea that bees might be implicated in were no medical records of mycotoxin is native to the region. the story was put forward by Professor poisoning if mycotoxins are naturally pro­ Nowicke said that apart from finding a Howard Meselson of Harvard University duced in the region. wide diversity of families in the samples she speaking at a meeting held last month at He added that although reports of has looked at, the only other detail she Tufts University, sponsored by the In­ yellow rain attacks appear to be seasonal­ could report was the size of the pollen the stitute for Foreign Policy Analysis. The a point in favour of a natural explanation grains. She said that the most common size spots became a focus for scientific in­ - the season in question is January to was 40 1-1m, although there was a large vestigations of yellow rain when they were March, a dry period when pollen produc­ number of very small grains of roughly 10 discovered, in February 1982, in Thailand tion is low. 1-1m . The State Department has argued that along the Kampuchean border. A team of Schiefer, a toxicologist who specializes these very small grains, which are able to Canadian medical investigators who were in mycotoxins, last summer prepared a penetrate the lungs deeply, would be an then in the area reported an outbreak of an report on yellow rain for the Canadian ideal carrier for the toxins. unidentified ailment among villagers at the Government after a visit to Thailand. A report on the US government's time the spots appeared, and analyses since Schiefer ticked off several other possible analyses of the pollen found in its samples carried out by the US government and explanations for the presence of pollen in is expected from the Army Chemical other countries confirm the presence of the spots. Systems Laboratory in a moqth or two. mycotoxins in the spots. • Yellow rain contains a sticky substance; Stephen Budiansky These are the toxins that the State Depart­ ment has accused the of manufacturing for use as a weapon in South-East Asia and Afghanistan. The finding that the spots also contain Changes in the incidence vast amounts of pollen came to light more recently. Last summer, Australian govern­ of suicide ment scientists found pollen in samples ob­ tained in Thailand, said to have come from within . The Australians concluded that the presence of pollen was so bizarre that the samples had to be "fakes", the R spots having been painted on the leaves (see E" 20· Nature 24 March, p.282). '0" But reports from the Canadian in­ ·u vestigators of the widespread appearance ~ to. of yellow spots in the Thailand border region, and the discovery of pollen in these samples, has made most investigators doubt that all could be deliberate fakes. Meselson was among the first to suggest that the presence of pollen in the spots might imply a natural phenomenon at work. Ac­ cording to participants at the Boston meeting (which was closed to reporters), SUICIDE is on the increase, particularly per cent increase in Hungary and a 34 per Meselson's hypothesis is based on the among women and the young, according to cent increase in Poland during the same known habit of bees to excrete large a report published by the World Health period. WHO claims that this apparent dis­ amounts of pollen at certain times of the Organization (WHO). Variations in crepancy can be at least partly explained by year. Meselson suggested that this could ex­ absolute rates have done little to change the the introduction of nontoxic natural gas plain the pollen spots on leaves; if the spots rank order of registered countries during supplles which made suicide by domestic were then attacked by the right species of the course of this century, although Britain gas poisoning impossible. Until 1960 this fungus, then the presence of has been an interesting exception to this was the most common method of suicide in mycotoxins could be explained as well. rule, showing a 34 per cent decrease in Britain. Source: Changing Patterns in Predictably, many objections were rais­ suicide rate since 1960, as opposed to a 49 Suicide Behaviour, WHO, Copenhagen. ed to Meselson's idea. According to Joan

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