Yellow rain was a 1981 political incident in which the United States Secretary of State Alexander Haig accused the Soviet Union of supplying T-2 mycotoxin to the communist states in Vietnam, Laos and Cambodia for use in counterinsurgency warfare. [1] Refugees described many different forms of "attacks", including a sticky yellow liquid falling from planes or helicopters, which was dubbed "yellow rain". The U.S. government alleged that over ten thousand people had been killed in attacks using these supposed chemical weapons. [2] The Soviets denied these claims and an initial United Nations investigation was inconclusive.
Samples of the supposed chemical agent that were supplied to a group of independent scientists turned out to be honeybee feces, suggesting that the "yellow rain" was due to mass defecation of digested pollen grains from large swarms of bees. [3] Although the scientific evidence conclusively showed that yellow rain was not a Soviet chemical or biological weapon, [4] [5] the U.S. government has not retracted its allegations, [6] arguing that the issue has not been fully resolved. [2] Many of the U.S. documents relating to this incident remain classified. [1]
The charges stemmed from events in Laos and North Vietnam beginning in 1975, when the two governments, which were allied with and supported by the Soviet Union, fought against Hmong tribes, peoples who had sided with the United States and South Vietnam during the Vietnam War. Refugees described events that they believed to be chemical warfare attacks by low-flying aircraft or helicopters; several of the reports were of a yellow, oily liquid that was dubbed "yellow rain". Those exposed claimed neurological and physical symptoms including seizures, blindness, and bleeding. Similar reports came from the Vietnamese invasion of Cambodia in 1978. [7]
A 1997 textbook produced by the U.S. Army Medical Department asserted that over ten thousand people were killed in attacks using chemical weapons in Laos, Cambodia and Afghanistan. [2] The descriptions of the attacks were diverse and included air-dropped canisters and sprays, booby traps, artillery shells, rockets and grenades that produced droplets of liquid, dust, powders, smoke or "insect-like" materials of a yellow, red, green, white or brown color. [2]
Secretary of State Alexander Haig announced in September 1981 that:
The Soviet Union described these accusations as a "big lie" and in turn correctly stated that the US government used chemical weapons during the Vietnam War. [8] The American accusations prompted a United Nations investigation in Pakistan and Thailand. This involved five doctors and scientists who interviewed alleged witnesses and collected samples that were purported to come from Afghanistan and Cambodia. However, the interviews produced conflicting testimony and the analyses of the samples were inconclusive. The UN experts also examined two refugees who claimed to be suffering from the after-effects of a chemical attack, but the refugees were instead diagnosed as having fungal skin infections. The team reported that they were unable to verify that chemical weapons had been used but noted that circumstantial evidence "suggestive of the possible use of some sort of toxic chemical substance in some instances." [9]
The US mycotoxin analyses were reported in the scientific literature in 1983 and 1984 and reported small amounts of mycotoxins called trichothecenes, ranging from the parts per million to traces in the parts per billion range. [10] [11] The lowest possible limit of detection in these mycotoxin analyses is in the parts per billion range. [12] However, several inconsistencies in these reports caused a "prolonged, and at times acrimonious, debate on the validity of the analyses". [13] A 2003 medical review notes that this debate may have been exacerbated since "Although analytical methods were in their infancy during the controversy, they were still sensitive enough to pick up low levels of environmental trichothecene contamination." [14]
C. J. Mirocha at the University of Minnesota conducted a biochemical investigation, looking for the presence of trichothecene mycotoxins, including T-2 toxin, diacetoxyscirpenol (DAS), and deoxynivalenol (DON). [10] This included chemical analyses of blood, urine, and tissue of alleged victims of chemical attacks in February 1982 in Laos and Kampuchea. "The finding of T-2, HT-2, and DAS toxins in blood, urine, and body tissues of alleged victims of chemical warfare in Southeast Asia provides compelling proof of the use of trichothecenes as nonconventional warfare agents. ... Additional significant findings lie in the trichothecenes found in the leaf samples (T-2, DON, nivalenol) and yellow powder (T-2, DAS). ... The most compelling evidence is the presence of T-2 and DAS in the yellow powder. Both toxins are infrequently found in nature and rarely occur together. In our experience, copious producers of T-2 toxin (F. tricinctum) do not produce DAS, and conversely, good producers of DAS (F. roseum 'Gibbosum') do not produce T-2." [10]
In 1983, these charges were disputed by Harvard biologist and biological weapons opponent Matthew Meselson and his team, who traveled to Laos and conducted a separate investigation. Meselson's team noted that trichothecene mycotoxins occur naturally in the region and questioned the witness testimony. He suggested an alternate hypothesis that the yellow rain was the harmless fecal matter of honeybees. [3] The Meselson team offered the following as evidence: separate "yellow rain drops" which occurred on the same leaf, and which were "accepted as authentic", consisted largely of pollen; each drop contained a different mix of pollen grains, as one would expect if they came from different bees, and the grains showed properties characteristic of pollen digested by bees (the protein inside the pollen grain was gone, while the outer indigestible shell remained). [15] Further, the pollen mix came from plant species typical of the area where a drop was collected. [16] [17]
The US government responded to these findings by arguing that the pollen was added deliberately, in order to make a substance that could be easily inhaled and "ensure the retention of toxins in the human body". [18] Meselson responded to this idea by stating that it was rather far-fetched to imagine that somebody would produce a chemical weapon by "gathering pollen predigested by honeybees." [17] The fact that the pollen originated in Southeast Asia meant that the Soviet Union could not have manufactured the substance domestically, and would have had to import tons of pollen from Vietnam. [19] : 35 Meselson's work was described in an independent medical review as providing "compelling evidence that yellow rain might have a benign natural explanation". [14]
After the honeybee hypothesis was made public, a literature search turned up an earlier Chinese paper [20] on the phenomenon of yellow droppings in Jiangsu Province in September 1976. Strikingly, the Chinese villagers had also used the term "yellow rain" to describe this phenomenon. Many villagers believed that the yellow droppings were portents of imminent earthquake activity. Others believed that the droppings were chemical weapons sprayed by the Soviet Union or Taiwan. However, the Chinese scientists also concluded that the droppings came from bees. [21] : 46
Analyses of putative "yellow rain" samples by the British, French and Swedish governments confirmed the presence of pollen and failed to find any trace of mycotoxins. [18] [22] Toxicology studies questioned the reliability of reports stating that mycotoxins had been detected in alleged victims up to two months after exposure, since these compounds are unstable in the body and are cleared from the blood in just a few hours. [13] An autopsy on a Khmer Rouge fighter named Chan Mann, a victim of a putative yellow rain attack in 1982, turned up traces of mycotoxins, but also aflatoxin, Blackwater fever, and malaria. [19] : 33
Surveys also showed that both mycotoxin-producing fungi and mycotoxin contamination were common in Southeast Asia, casting doubt on the assertion that detecting these compounds was an unusual occurrence. [23] [24] For example, a Canadian military laboratory found mycotoxins in the blood of five people from the area who had never been exposed to yellow rain, out of 270 tested, but none in the blood of ten alleged victims, [17] [25] and a 1988 paper reported that illnesses from mycotoxin exposure may pose a serious threat to public health in Malaysia. [26] It is now recognized that mycotoxin contamination of foods such as wheat and maize is a common problem, particularly in temperate regions of the world. [24] [27] As noted in a 2003 medical review, "The government research highlighted, if nothing else, that natural mycotoxicoses were an important health hazard in Southeast Asia." [14]
In 1987, the New York Times reported that Freedom of Information requests showed that field investigations in 1983–85 by US government teams had produced no evidence to substantiate the initial allegations and instead cast doubt on the reliability of the initial reports, but these critical reports were not released to the public. [28] A 1989 analysis of the initial reports gathered from Hmong refugees that was published in the Journal of the American Medical Association noted "marked inconsistencies that greatly compromised the validity of the testimony" and criticized the methods used in interviews by the US Army medical team that gathered this information. These issues included the US Army team only interviewing those people who claimed to have knowledge of attacks with chemical weapons and the investigators asking leading questions during interviews. The authors noted that individuals' stories changed over time, were inconsistent with other accounts, and that the people who claimed to have been eyewitnesses when first interviewed later stated that they had been relaying the accounts of others. [29]
In 1982, Meselson had visited a Hmong refugee camp with samples of bee droppings that he had collected in Thailand. Most of the Hmong he interviewed claimed that these were samples of the chemical weapons that they had been attacked with. One man accurately identified them as insect droppings, but switched to the chemical weapons story after discussion with fellow Hmong. [21] : 46
Australian military scientist Rod Barton visited Thailand in 1984, and discovered that Thai villagers were blaming yellow rain for a variety of ailments, including scabies. An American doctor in Bangkok explained that the United States had been taking a special interest in yellow rain, and was providing medical care to alleged victims. [19] : 39–40
A CIA report from the 1960s reported allegations by the Cambodian government that their forces had been attacked with chemical weapons, leaving behind a yellow powder. The Cambodians blamed the United States for these alleged chemical attacks. Some of the samples of "yellow rain" collected from Cambodia in 1983 tested positive for CS, which the United States had used during the Vietnam War. CS is a form of tear gas and is not acutely toxic, but may account for some of the milder symptoms reported by the Hmong villagers. [19] : 39
The scientific community sees these allegations as supported by insufficient evidence, or as having been completely refuted. For instance, a 1992 review published in Politics and the Life Sciences described the idea of yellow rain as a biological agent as conclusively disproved and called for an assessment by the US government of the mistakes made in this episode, stating that "the present approach of sweeping the matter under the rug and hoping people will forget about it could be counterproductive." [25] Similarly, a 1997 review of the history of biological warfare published in the Journal of the American Medical Association stated that the yellow rain allegations are "widely regarded as erroneous", [5] a 2001 review in the Annual Reviews in Microbiology described them as "unsubstantiated for many reasons", [30] and a 2003 article in Annual Review of Phytopathology described them as "largely discredited". [4] A 2003 review of the history of biological warfare described these allegations as one of many cases where states have produced propaganda containing false or unsubstantiated accusations of the use of biological weapons by their enemies. [31]
In contrast, as of 1997 the U.S. Army maintains that some experts believe that "trichothecenes were used as biological weapons in Southeast Asia and Afghanistan" although they write that "it has not been possible for the United States to prove unequivocally that trichothecene mycotoxins were used as biological weapons." They argued that presence of pollen in yellow rain samples is best explained by the idea that "during biological warfare attacks, dispersed trichothecenes landed in pollen-containing areas." [2] (Essentially the same position is taken in a subsequent volume in the same series of U.S. Army textbooks published in 2007. [32] ) Similarly, the US Defense Threat Reduction Agency argues that the controversy has not been resolved and states that a CIA report indicated the Soviet Union did possess weapons based on T-2 mycotoxin, although the agency states that "no trace of a trichothecene-containing weapon was ever found in the areas affected by yellow rain" and concludes that the use of such weapons "may never be unequivocally proved." [33] A 2007 review published in Politics and the Life Sciences concluded that the balance of evidence strongly supported the hypothesis that some type of chemical or biological weapon was used in Southeast Asia in the late 1970s and early 1980s, but noted that they found no definitive proof of this hypothesis and that the evidence could not "identify the specific agents used, the intent, or the root source or sources of the attacks." [34] The Vietnamese and the Soviets have also reportedly used other chemical weapons in conflict, in Cambodia and Afghanistan, respectively. [35] [36] [37]
An episode of mass pollen release from bees in 2002 in Sangrampur, India, prompted unfounded fears of a chemical weapons attack, although this was in fact due to a mass migration of giant Asian honeybees. This event revived memories of what New Scientist described as "cold war paranoia", and the article noted that the Wall Street Journal had covered these 1980s yellow rain allegations in particular detail. [38] Indeed, the Wall Street Journal continues to assert that the Soviet Union used yellow rain as a chemical weapon in the 1980s and in 2003 accused Matthew Meselson of "excusing away evidence of Soviet violations." [39]
In the build-up to the 2003 invasion of Iraq the Wall Street Journal alleged that Saddam Hussein possessed a chemical weapon called "yellow rain". [40] The Iraqis appear to have investigated trichothecene mycotoxins in 1990, but only purified a total of 20 ml of the agent from fungal cultures and did not manage to scale up the purification or produce any weapons containing these compounds. [41] Although these toxins are not generally regarded as practical tactical weapons, [42] the T-2 toxin might be a usable weapon since it can be absorbed through the skin, although it would be very difficult to manufacture it in any reasonable quantity. [43]
Henry Wilde, a retired US Foreign Service Officer, has drawn parallels between the use of yellow rain allegations by the US government against the Soviet Union and the later exaggerated allegations on the topic of Iraq and weapons of mass destruction. [44] Wilde considers it likely that states may again "use rumors and false or planted intelligence of such weapons use for propaganda purposes." and calls for the establishment of a more rigorous inspection process to deal with such claims. [44] Similar concerns were expressed in a 2006 review published by the World Organisation for Animal Health, which compared the American yellow rain accusations to other Cold War-era accusations from the Soviet Union and Cuba, as well as to more recent mistaken intelligence on Iraqi weapons capabilities, concluding that such unjustified accusations have encouraged the development of biological weapons and increased the risk that they might be used, as they have discredited arms-control efforts. [45]
In 2012 the science-themed show Radiolab aired an interview with Hmong refugee Eng Yang and his niece, author Kao Kalia Yang, to discuss Eng Yang's experience with yellow rain. The hosts took the position that yellow rain was unlikely to have been a chemical agent. The episode prompted a backlash among some listeners, who criticized Robert Krulwich for insensitivity, racism, and their disregard for Yang's personal and professional experience with the region in question. [46] [47] The negative response prompted host Krulwich to issue an apology for his handling of the interview. [48]
On 23 May 2015, just before the national holiday of 24 May (the day of Bulgarian writing and culture), yellow rain fell in Sofia, Bulgaria. Suspicions were raised because the Bulgarian government was criticizing Russian actions in Ukraine at the time. The Bulgarian national academy BAN explained the event as flower pollen. [49]
American Hmong poet Mai Der Vang published Yellow Rain (Graywolf Press, 2021) to critical acclaim and was a 2022 Finalist for the Pulitzer Prize in Poetry. [50] The book explores yellow rain in Southeast Asia through the use of documentary poetics.
Biological warfare, also known as germ warfare, is the use of biological toxins or infectious agents such as bacteria, viruses, insects, and fungi with the intent to kill, harm or incapacitate humans, animals or plants as an act of war. Biological weapons are living organisms or replicating entities. Entomological (insect) warfare is a subtype of biological warfare.
The Biological Weapons Convention (BWC), or Biological and Toxin Weapons Convention (BTWC), is a disarmament treaty that effectively bans biological and toxin weapons by prohibiting their development, production, acquisition, transfer, stockpiling and use. The treaty's full name is the Convention on the Prohibition of the Development, Production and Stockpiling of Bacteriological (Biological) and Toxin Weapons and on their Destruction.
A mycotoxin is a toxic secondary metabolite produced by fungi and is capable of causing disease and death in both humans and other animals. The term 'mycotoxin' is usually reserved for the toxic chemical products produced by fungi that readily colonize crops.
Fusarium is a large genus of filamentous fungi, part of a group often referred to as hyphomycetes, widely distributed in soil and associated with plants. Most species are harmless saprobes, and are relatively abundant members of the soil microbial community. Some species produce mycotoxins in cereal crops that can affect human and animal health if they enter the food chain. The main toxins produced by these Fusarium species are fumonisins and trichothecenes. Despite most species apparently being harmless, some Fusarium species and subspecific groups are among the most important fungal pathogens of plants and animals.
T-2 mycotoxin is a trichothecene mycotoxin. It is a naturally occurring mold byproduct of Fusarium spp. fungus which is toxic to humans and other animals. The clinical condition it causes is alimentary toxic aleukia and a host of symptoms related to organs as diverse as the skin, airway, and stomach. Ingestion may come from consumption of moldy whole grains. T-2 can be absorbed through human skin. Although no significant systemic effects are expected after dermal contact in normal agricultural or residential environments, local skin effects can not be excluded. Hence, skin contact with T-2 should be limited.
Matthew Stanley Meselson is a geneticist and molecular biologist currently at Harvard University, known for his demonstration, with Franklin Stahl, of semi-conservative DNA replication. After completing his Ph.D. under Linus Pauling at the California Institute of Technology, Meselson became a Professor at Harvard University in 1960, where he has remained, today, as Thomas Dudley Cabot Professor of the Natural Sciences.
On 2 April 1979, spores of Bacillus anthracis were accidentally released from a Soviet military research facility in the city of Sverdlovsk, Soviet Union. The ensuing outbreak of the disease resulted in the deaths of at least 68 people, although the exact number of victims remains unknown. The cause of the outbreak was denied for years by the Soviet authorities, which blamed the deaths on consumption of tainted meat from the area, and subcutaneous exposure due to butchers handling the tainted meat. The accident was the first major indication in the Western world that the Soviet Union had embarked upon an offensive programme aimed at the development and large-scale production of biological weapons.
The trichothecenes are a large family of chemically related mycotoxins. They are produced by various species of Fusarium, Myrothecium, Trichoderma/Podostroma, Trichothecium, Cephalosporium, Verticimonosporium, and Stachybotrys. Chemically, trichothecenes are a class of sesquiterpenes.
The fumonisins are a group of mycotoxins derived from Fusarium and their Liseola section. They have strong structural similarity to sphinganine, the backbone precursor of sphingolipids.
Mycotoxicology is the branch of mycology that focuses on analyzing and studying the toxins produced by fungi, known as mycotoxins. In the food industry it is important to adopt measures that keep mycotoxin levels as low as practicable, especially those that are heat-stable. These chemical compounds are the result of secondary metabolism initiated in response to specific developmental or environmental signals. This includes biological stress from the environment, such as lower nutrients or competition for those available. Under this secondary path the fungus produces a wide array of compounds in order to gain some level of advantage, such as incrementing the efficiency of metabolic processes to gain more energy from less food, or attacking other microorganisms and being able to use their remains as a food source.
Jeanne Harley Guillemin was an American medical anthropologist and author, who for 25 years taught at Boston College as a professor of Sociology and for over ten years was a senior fellow in the Security Studies Program at Massachusetts Institute of Technology. She was an authority on biological weapons and published four books on the topic.
The United States biological weapons program officially began in spring 1943 on orders from U.S. President Franklin D. Roosevelt. Research continued following World War II as the U.S. built up a large stockpile of biological agents and weapons. Over the course of its 27-year history, the program weaponized and stockpiled seven bio-agents — Bacillus anthracis (anthrax), Francisella tularensis (tularemia), Brucella spp (brucellosis), Coxiella burnetii (Q-fever), Venezuelan equine encephalitis virus, Botulinum toxin (botulism), and Staphylococcal enterotoxin B. The US also pursued basic research on many more bio-agents. Throughout its history, the U.S. bioweapons program was secret. It was later revealed that laboratory and field testing had been common. The official policy of the United States was first to deter the use of bio-weapons against U.S. forces and secondarily to retaliate if deterrence failed.
Satratoxin-H, a trichothecene mycotoxin, is a naturally occurring toxin produced by the ascomycetes Stachybotrys chartarum and Podostroma cornu-damae which is highly toxic to humans and animals. The clinical condition it causes is known as Stachybotrotoxicosis. It is related to the mycotoxin T-2, but unlike T-2 has not been reported to have been used as a chemical weapon.
Fusarium sporotrichioides is a fungal plant pathogen, one of various Fusarium species responsible for damaging crops, in particular causing a condition known as Fusarium head blight in wheat, consequently being of notable agricultural and economic importance. The species is ecologically widespread, being found across tropical and temperate regions, and is a significant producer of mycotoxins, particularly trichothecenes. Although mainly infecting crops, F. sporotrichioides-derived mycotoxins can have repercussions for human health in the case of the ingestion of infected cereals. One such example includes the outbreak of alimentary toxic aleukia (ATA) in Russia, of which F. sporotrichioides-infected crop was suspected to be the cause. Although current studies on F. sporotrichioides are somewhat limited in comparison to other species in the genus, Fusarium sporotrichioides has found several applications as a model system for experimentation in molecular biology.
The "Statement on Chemical and Biological Defense Policies and Programs" was a speech delivered on November 25, 1969, by U.S. President Richard Nixon. In the speech, Nixon announced the end of the U.S. offensive biological weapons program and reaffirmed a no-first-use policy for chemical weapons. The statement excluded toxins, herbicides and riot-control agents as they were not chemical and biological weapons, though herbicides and toxins were both later banned. The decision to ban biological weapons was influenced by a number of domestic and international issues.
Entomological warfare (EW) is a type of biological warfare that uses insects to interrupt supply lines by damaging crops, or to directly harm enemy combatants and civilian populations. There have been several programs which have attempted to institute this methodology; however, there has been limited application of entomological warfare against military or civilian targets, Japan being the only state known to have verifiably implemented the method against another state, namely the Chinese during World War II. However, EW was used more widely in antiquity, in order to repel sieges or cause economic harm to states. Research into EW was conducted during both World War II and the Cold War by numerous states such as the Soviet Union, United States, Germany and Canada. There have also been suggestions that it could be implemented by non-state actors in a form of bioterrorism. Under the Biological and Toxic Weapons Convention of 1972, use of insects to administer agents or toxins for hostile purposes is deemed to be against international law.
Microbial toxins are toxins produced by micro-organisms, including bacteria, fungi, protozoa, dinoflagellates, and viruses. Many microbial toxins promote infection and disease by directly damaging host tissues and by disabling the immune system. Endotoxins most commonly refer to the lipopolysaccharide (LPS) or lipooligosaccharide (LOS) that are in the outer plasma membrane of Gram-negative bacteria. The botulinum toxin, which is primarily produced by Clostridium botulinum and less frequently by other Clostridium species, is the most toxic substance known in the world. However, microbial toxins also have important uses in medical science and research. Currently, new methods of detecting bacterial toxins are being developed to better isolate and understand these toxins. Potential applications of toxin research include combating microbial virulence, the development of novel anticancer drugs and other medicines, and the use of toxins as tools in neurobiology and cellular biology.
Before the 20th century, the use of biological agents took three major forms:
Nivalenol (NIV) is a mycotoxin of the trichothecene group. In nature it is mainly found in fungi of the Fusarium species. The Fusarium species belongs to the most prevalent mycotoxin producing fungi in the temperate regions of the northern hemisphere, therefore making them a considerable risk for the food crop production industry.
Rebecca Katz is a professor and director of the Center for Global Health Science and Security at Georgetown University Medical Center. She is an expert in global health and international diplomacy, specializing in emerging infectious diseases. From 2004 to 2019, she was a consultant for the United States Department of State on matters related to the Biological Weapons Convention and emerging infectious disease threats. Katz served on the Joe Biden presidential campaign's public health panel to advise on the COVID-19 pandemic.
Yellow rain is the excrement of jungle bees. It's yellow from digested pollen grains, and it rains down from swarms of bees too high to be seen. His theory turns out to be exactly right. The Government's own studies, still unpublished, prove that the source is bees, not bombs.
Eyewitnesses claimed that Yellow Rain smelled like gunpowder and left a residue of sticky yellow spots on leaves, rocks, and rooftops. Exposure to high doses reportedly caused heavy bleeding from the nose and gums, blindness, tremors, seizures, other neurological symptoms, and death. Similar incidents were reported in Democratic Kampuchea (Cambodia) in 1978, after the Vietnamese Army invaded that country to topple the dictator Pol Pot and his murderous Khmer Rouge regime.