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Aum Shinrikyo, Part 1: What really happened 21 years ago?

Aum Shinrikyo, Part 1: What really happened 21 years ago?

The following is the first in a series examining Aum Shinrikyo and the Tokyo subway attack of 1995. It is adapted from an article on the subject I am preparing for submission to an academic journal. While the work is my own, it benefited greatly from input provided by my old colleague Scott Cormier. Thanks Scott. – (Brad Trefz, 7 April, 2016).

Kasumigaseki Station, Tokyo Japan. Focus of the 1995 attack. (Source: Wikipedia Commons)

The 1995 Aum Shinrikyo attack on the Tokyo subway system was a seminal event in the history of chemical, biological, radiological, and nuclear (CBRN) weapons. It marked the first major use of a Chemical weapon by a non-state actor that received widespread worldwide attention, and led to efforts to combat the threat of CBRN terrorism around the world. Much of the CBRN professional community as it is today, emergedfrom the Aum attack, from the Civil Support Teams-WMD to the Anthrax vaccination program in the military.

March 20, 2016 marked the 21st anniversary of the attack. Over the last year, Aum members have made the news in several places around the world (here, here, here, here, and here), and their leader Shoko Asahara (realname: Chizuo Matsumoto) continues to delay his execution, though that may be nearing an end. Nearly a dozen other members of the group associated with the Tokyo subway attack also await execution, while dozens more either served or are serving long sentences.  While the cult (renamed Aleph) persists, it is splintered and persecuted.

Despite the Aum news that usually appears around this time of year (March/April is peak terrorist) alongside remembrances of the OKC bombing, the Boston Marathon, Columbine, and the first chemical attack at Second Ypres in 1915, Aum is generally not a threat any longer, even if their memory is institutionalized in the CBRN community. More problematic is the fact that almost everything everyone thinks they know about the 1995 Tokyo subway attack is usually incorrect, inaccurate, or just plain wrong.

Aum Shinrikyo (Supreme Truth) is a pseudo-scientific, syncretistic religious group founded by Shoko Asahara (born Chizuo Matsumoto), a yoga instructor, acupuncturist, and masseuse in 1987. Asahara was believed to have obtained spiritual fulfillment as a “wandering monk” and have been ordained by a deity as the “god of light who leads the armies of the gods” in an ultimate war to destroy darkness and bring about the kingdom of Shambhala – a Buddhist utopian society of spiritually realized individuals. In reality, Asahara was part con man and part lunatic. His religious following grew quickly in the mid and late 1980’s. By 1990, he had developed a close inner circle of accomplished technicians, engineers, and scientists whom he put to work on a chemical and biological weapons (CBW) program. Asahara was convinced that his CBW program would allow him to bring about the final battle between good and evil. In his construct, the United State represented the forces of evil (Asahara had been a fan of Mao and dabbled in leftist radicalism in the 1970’s).[1]

Between 1990 and 1995, the cult attempted 17 known chemical or biological attacks.[2]  Ten of the attacks involved chemicals or chemical weapons, and seven attempted to use biological agents. The chemical program was the only one to meet with success, with the 1995 subway attack representing the group’s apogee. The final attack was a rushed affair, and brought about the groups general demise. The attack was the result of police closing in on the organization, which funded itself through a variety of illicit means. The group tried building rifles and stockpiling other weapons in violation of Japan’s strict gun-control laws. These brought the attention of the Japanese police, and Asahara was determined to spark his apocalypse, or at least disrupt the police effort.

Surprisingly, the Japanese Police were aware of Aum’s sarin production, having obtained samples and proof four months prior to the attack. Shockingly, there was no law against its production in Japan at the time so police continued to investigate in hope of making their case on other charges.[3] More worrisome was the fact that the samples obtained by the police were not linked to the cult’s attack on Matsumoto city in June of 1994, an attack that killed as many as a dozen people and sickened at least 200 more.

Initially Japanese police focused their investigation in Matsumoto on Yoshiyuki Kono a man whose home was in the attack area and whose wife was a victim (she spent the next 14 years in a coma, dying in 2008). Kono came to the attention of authorities due to the large amount of organophosphate pesticide that found stored in his home. Sarin is, of course, an organophosphate and the symptoms for severe exposure to such pesticide or to nerve agent are identical. The police were initially unaware of Aum’s involvement. Kono was the first of what would be a long list of persons of interest in terrorism cases whose subsequent media ordeal seemed to do little to deter repeat performances. Kono could be in an exclusive club with Richard Jewel and Steven J. Hatfill.    

Eventually, police realized their error – after the Tokyo attack. In the intervening nine months, Aum Shinrikyo came to the attention of police for other reasons. A campaign of assassination, kidnapping, and the acquisition of illegal firearms added to a growing list of offenses involving cult members. The Japanese police, still largely unaware of the cult’s chemical and biological arsenal, planned carry out simultaneous raids of cult facilities throughout the country in March 1995. A leak to a major Japanese newspaper tipped off the cult as to the police investigation, leading the cult to respond ahead of the raids. As the net closed in, Asahara and his closest followers devised the Tokyo attack as a diversion, hoping to target the Police Headquarters in Tokyo.

On March 20, 1995, five members of the cult boarded different, converging subway trains in Tokyo. Each carried at least two packages, with approximately 600 mL of a viscous liquid in two layers, with the 400 mL dark brown bottom layer consisting of a mixture of the chemical agent sarin, hexane, and N,N-diethlaniline.[4] The cult members wrapped these sealed plastic bags containing the agent in newspaper and carried them in bags to avoid suspicion. The attackers boarded trains travelling in both directions along three separate lines, which converged on Kasumigaseki station, the station nearest police headquarters in Tokyo. The cult’s hope was that the trains would be full of police, known to carry out their shift change at 8:30 a.m.[5] 

During the height of morning rush hour as trains converged on the target area the members placed the packages on the floor of the train and pierced the packages using sharpened points on umbrellas. In total, the cult effectively deployed eight of the eleven packages between 7:46 a.m. and 8:01 a.m.[6] A later estimation determining a total of 159 ounces of the chemical mixture released in total on the five separate trains.[7] In part, the failure to deploy two of the packages was due to last minute reluctance on the part of one individual involved in the attack, and in the other, it was likely the result of a failure to pierce the package.

The cult members departed the trains and reportedly self-administered atropine injections as an antidote against accidental exposure.[8] Within minutes, individuals on the trains and at least one worker who discovered and handled one of the packages began to show signs and symptoms of organophosphate poisoning. These symptoms varied according to dose. Mild nerve agent exposure usually manifests as pinpointed pupils, while excessive salivation, tearing, loss of bladder and bowel control, gastro-intestinal distress, and vomiting are typically observed in more acute dosages.[9] Muscular twitching, convulsions, and respiratory distress followed by heart arrhythmia leading to heart failure are the most severe symptoms and usually precede death, unless quickly treated. Additional stations and passengers were contaminated as trains continued on to other stations past Kasumigaseki.

As individuals began to suffer from nerve agent symptoms and victims began streaming from subway stations in the area, the emergency services responded, initially believing it to be a gas leak. It was three hours into the event before the Tokyo Police identified sarin as the cause, and then only because the cult had used it previously in the Matsumoto attack the previous year (someone must have connected the two).[10] In the interim, contaminated casualties, worried well, bystanders, first responders, hospital emergency rooms, and medical workers all comingled, with secondary contamination resulting. Several secondary casualties among first responders resulted.


Figure 1 - Casualties outside a subway station during the attack

The Tokyo fire department got its first notification at 8:09 a.m., followed in rapid succession with more calls from the affected subway stations.[12] Out of Tokyo’s 1,650 emergency medical technicians (EMT) and 182 ambulances, 1,364 EMTs and 131 ambulances deployed to the three downtown subway stations.[13] This represented a commitment of 72% of the medical systems ambulances and 83% of its EMTs. None of the EMTs, police, or fire personnel that initially responded wore protective measures until approximately forty minutes into the response when the National Police Agency ordered anyone going into the subway system (which had been shut down by that point) to wear gas masks.[14] Initially St. Luke’s Hospital, informed by the Fire Department of a gas explosion in the subway system, prepared to receive burn and carbon monoxide poisoning casualties.[15] 

At 8:28 a.m. the first casualty arrived at St. Luke’s, on foot.[16] St. Luke’s was within three kilometers of seven of 15 stations reporting casualties and was nearest the epicenter of the attack.[17] This initial casualty brought the information that there was no explosion and was suffering from visual problems. Additional casualties began to arrive. The first by ambulance arrived at 8:43 a.m. By the end of the first hour, 498 patients, including three in cardiac arrest, arrived at the St. Luke’s Emergency Room (see Table 1).

    Table 1 - Patient Mode of Transport St. Lukes International Hospital

Mode       CasualtiesPercentage

On foot                       174                     34.9

Taxi                             120                     24.1

Car (passerby)                67                     13.5

Tokyo FD                      64                     12.9

Ambulance                    35                       7

Police Car                        7                       1.4

Other                         31                    6.2

Total                              498                       100

  Source: Okumura, et al., “Part 2: Hospital Response”, 614.

Figure 2 - Casualties arrive by Ambulance at St. Luke's (Source: Chikumo Chiaki, AP Wide World Photos)

St. Luke’s implemented its disaster procedures based on earthquake plans. The hospital cancelled routine operations and outpatient exams. St. Luke’s staff had 36 residents, 129 staff doctors, 477 nurses, 68 clerks, and an average of 30 volunteers a day. The hospital initiated staff re-calls and mobilized the students of the co-located College of Nursing to assist. In addition to the 498 patients arriving from the disaster, St. Luke’s typically handled 2,000 outpatients per day and despite the cancellations, these patients continued to arrive. The hospital had no plan for the guidance of mass casualties and allowed free access via its three entrances throughout the disaster. Victims, family members, co-workers, television crews, curious on-lookers, worried well, and regular patients all co-mingled. No decontamination occurred, at the hospital or at the incident site.[18]  

Figure 4 – Mild casualties at St. Luke's (Source: Haruyoshi Yamaguchi/Sygma/Corbis)

After three hours when the hospital confirmed the agent as sarin from television reports of the Tokyo Police press conference, admitted patients with moderate to severe symptoms were decontaminated. Decontamination of non-admitted casualties did not occur because the hospital had no decontamination or shower area to accommodate the large number of mild cases. Workers packaged victim clothing left in hospital wards in sealed plastic bags. Within the hospital surge capacity expanded to the hospital chapel, a prepared site for such eventuality, but one with limited ventilation. Contaminated casualties in this area resulted in higher concentrations, and 46 percent of those working in this area reported acute symptoms.

Following the attack, at least 472 hospital workers at St. Luke’s reported symptoms of nerve agent exposure, though some of these may have been psychosomatic as they were self-reported sometime after the attack. Of note, of the 110 persons citing symptoms consistent with acute nerve agent poisoning, all of them were female. There were no severe cases of secondary exposure among hospital staff, and only one nurse, who had worked in the chapel area for the entire day, required admission with acute symptoms, though she recovered within a few days. [19]

At the incident site, Emergency Medical Technician (EMT) teams suffered limitations that were integral to the Japanese Emergency Medical System (EMS). The three man ambulance teams consisted of two EMT’s equivalent to an American EMT-B and one Emergency Life-Saving Technician (ELST) roughly equivalent to an American paramedic. Standing orders like those for paramedics in the U.S. did not exist and ELSTs required permission from the doctor assigned to the Tokyo Metropolitan Ambulance Control Center (TMACC) before they could carry out invasive procedures. In addition, Japanese law forbids ELSTs from conducting endotracheal intubations.[20] Airway maintenance is a key component of emergency medicine and is especially vital in chemical casualties.  

The system completely broke down due to the number of units and casualties involved. TMACC communications broke down unable to handle the call volume and ELSTs carried out little airway management and only one patient received an IV, and then only because a bystander who happened to be a doctor gave the order. Intubation and ventilation of severe casualties occurred entirely at hospitals. Triage at the scene was minimal as casualties self-evacuated the stations,  and arrived at St. Luke’s with no triage tags. Because of the breakdown in the Tokyo Metropolitan Fire Department (TMFD) and TMACC systems casualties flow to hospitals were unmanaged. It was sixteen hours after the initial attack until an accurate accounting of casualties’ location was completed. In the end, St. Luke’s received the bulk of the casualties.[21]

While St. Luke’s was able to accommodate the initial influx, it later noted it was at capacity quickly. Had additional casualties arrived after the first hours, the hospital would have been unable to accommodate them and would have required inter-hospital transport. This was not available due to the breakdown in the TMACC system and in any case, nearly all their assets were at incident scenes. Because of the lack of decontamination and protective measures, of the 1,364 EMT’s responding, 135 (9.9%) showed acute symptoms of nerve agent exposure that required treatment at hospitals. In large part, these were the result of casualties transported by ambulance with the crews exposed in the confined space. As these responders showed symptoms, an order went out to open all windows on ambulances to increase ventilation of the vehicles.

The attack killed 12 and 1,046 were admitted to 98 different hospitals in and around Tokyo for agent exposure of varied severity.[22] The bulk of the casualties experienced mild symptoms, mostly blurred vision resulting from pinpointed pupils. At St. Luke’s, 640 patients were treated on an outpatient basis on the first day and 111 were admitted with more moderate or severe symptoms.[23] Over the course of the following week, additional patients were treated and continued to arrive at the hospital with the largest number arriving on March 23 and 24 - 319 and 204 respectively - with only 15 of these admitted.[24] 

St. Luke’s has 520 beds. It received the largest number of victims, 640on the day of the attack and an additional 770 in the week after the attack.[25] An additional 5,510 “victims” reported to 278 different hospitals and clinics in the Tokyo area the day of attack.[26] More arrived in the days that followed. Some of these were far from the attack site. Japanese officials later reported to American investigators that almost 74 percent of the total “casualties” were psychological , though some reports put this number as high as 85 percent.[27] According to a briefing after the event given by the Japanese to unspecified American medical researchers of the 5,100 casualties reporting to medical facilities, 4,470 showed no symptoms of nerve agent exposure. 

The majority of these treated suffered symptoms consistent with mild nerve agent poisoning. Exposure to organophosphates, like sarin is detected by monitoring cholinesterase levels in blood.[28]  At least some portion of those admitted to St. Luke’s were observed to have low levels ofplasma cholinesterase.[29]  Interestingly, at least three individuals admitted to St. Luke’s following the attack were found to have plasma cholinesterase levels in the normal range, and were admitted to the hospital with severe symptoms.[30]  This suggests even those admitted to the hospital and traditionally labeled as casualties, may not have been suffering from nerve agent exposure. The symptoms of mild nerve agent poisoning like headaches, nausea, and dizziness mirror those caused by acute stress and panic attacks. In addition, some of the long-term effects attributed to sarin exposure mirror those of some PTSD patients.[31]

Serious cases received injections of atropine and pralidoxime, the preferred antidote treatment, over the course of 1-2 days.[32]  Mild nerve agent symptoms and treatment are not generally believed to have significant long-lasting side effects in otherwise healthy individuals, though one study of Tokyo casualties suggests there may be long term neurological effects in some individuals.[33]  There is also a significantly higher incidence of PTSD noted in this group. Twenty to twenty-five percent of the 640[S23]  St. Luke patients, tested as high risk for PTSD, two years after the attack.[34]

The distinction between these types of casualties blurs in history, the media, and professional assessment. Most works and reports on the Aum Shinrikyo subway attack tend to cite 5,000 to 6,000 casualties with no distinction between types of casualty.[35] Some of the more outlandish sources even use figures as high as 10,000.[36] The majority of accounts about the attack and Aum Shinrikyo cite media reports for their casualty figures. The numbers collected and published by the staff at St. Luke’s hospital, as referenced above, are the only known accurate accounting.

In our next post on the Tokyo Subway attack we’ll break down the points of failure in the response and examine ways planning and emergency management can improve community resilience to such events. We will also talk about the significant problem of “worried well” that is inherent in most CBRN events. Until then follow us on facebook for the latest. 


[1] Robert Jay Lifton, Destroying the World to Save It: Aum Shinrikyo, Apocalyptic Violence, and the New Global Terrorism (New York: Henry Holt and Company, 1999).

[2] Center for Non-proliferation Studies, “Chronology of Aum Shinrikyo CBW Activities.” Monterey Institute of International Studies, http://cns.miis.edu (accessed March 12, 2013).

[3] Amy E Smithson and Leslie Ann Levy,  Ataxia:* The Chemical and Biological Terrorism Threat and the US Response, Henry L. Stimson Paper No. 35 (Washington, DC: Henry L. Stimson Center, 2000), 84.

[4] R.M. Bowler, K. Murai, and R.H. True, “Update and Long-term Sequelae of the Sarin Attack in the Tokyo, Japan Subway,” Chemical Health and Safety January/February (2001): 53-55.There are conflicting reports about the actual content of the packages and the purity of the substance employed.  A member of the Federal Bureau of Investigation Hazardous Materials Team confided in 2002 to the author “it wasn’t ‘quite’ Sarin.” Whether the substance analyzed contained Sarin, or an organophosphate close to Sarin, is irrelevant.  The purity level was low, as evidenced by the other contaminants in the liquid, and cult members own admissions under questioning later. A recent article by Japanese police forensic scientists identified it as “30 percent sarin.” The presence of hexane suggests an attempt to produce cyclosarin, a variant of the agent. See Tetsu Okumura, Yasuo Seto, Akira Fuse, “Countermeasures against chemical terrorism in Japan,” Forensic Science International, 227, no. 1–3 (April  2-6, See alsoD.W. Brackett, Holy Terror: Armageddon in Tokyo (New York: Weatherhill, 1996), 117-118, 125; Anthony T. Tu, “Aum Shinrikyo’s Chemical and Biological Weapons,” Archives of Toxicology, Kinetics and Xenobiotic Metabolism 7, no. 3 (Autumn 1999).

[5] Ibid, 87. Smithson notes there are varied reports as to some of the details about the targeting and planning of the operation, but the consensus is that the goal was to “kill as many policemen as possible.” See Kyle B. Olson, “Aum Shinrikyo: Once and Future Threat?” Emerging Infectious Diseases 5, no. 4 (July/August 1999): 516.

[6] Smithson and Levy. 

[7] Smithson and Levy 89; Brackett, 134-140.

[8] The attackers also took pyristigmine bromide pills several hours before the attack, a pre-treatment for potential nerve agent exposure. See Smithson and Levy, 88; Kaplan, David E. and Andrew Marshall, The Cult at the End of the World (New York: Crown Publishers, Inc., 1996), 243; Brackett, 129.

[9] The acronym SLUDGE is used to remember the symptoms of organophosphate poisoning – Salivation, Lachrymation, Urination, Defecation, Gastrointestinal Distress, and Emesis.

[10] Center for Non-proliferation Studies.

[11] Tetsu Okumura, Kouichiro Suzuki, Atsuhiro Fukuda, Akitsugu Kohama, Nobukatsu Takasu,Shinichi Ishimatsu, Shigeaki Hinohara, “The Tokyo Subway Sarin Attack: Disaster Management, Part 1: Community Emergency Response.” Academic Emergency Medicine 5, no. 6 (June 1998): 613-617.  Staff from St. Luke’s Hospital who experienced the attack wrote this article, one of three. Together these constitute the only solid academic sources in English from actual participants in the response.

[12] Smithson and Levy, 91.

[13] Smithson and Levy 91. Brackett, 2.

[14] Ibid.See also Okumura,et.al.

[15] Tetsu Okumura,  Kouichiro Suzuki, Atsuhiro Fukuda, Akitsugu Kohama, Nobukatsu Takasu,Shinichi Ishimatsu, Shigeaki Hinohara, “The Tokyo Subway Sarin Attack: Disaster Management, Part 2: Hospital Response.” Academic Emergency Medicine 5, no. 6 (June 1998): 618-624.

[16] Ibid, 619.

[17] Ibid.

[18] Ibid. 

[19] Ibid, 620-621.

[20] Okumura, et al., “Part 1: Community Emergency Response,” 614-615.

[21] Ibid.

[22] Okumura, et al., “Part 1: Community Disaster Response”.

[23] Okurmura, et al., “Part 2: Hospital Response,” 619.

[24] Ibid.

[25] Ibid.

[26]Smithson and Levy 95. See also David E. Kaplan, “Aum Shinrikyo (1995),” in Toxic Terror: Assessing Terrorist Use of Chemical and Biological Weapons, ed. Jonathan B. Tucker (Cambridge, MA: MIT Press, 2000), 219. Twelve victims died of cardiopulmonary arrest within the first 48 hours. A few victims who suffered serious exposure and required extensive long-term treatment have since died, including one in a coma who died in 2008. Thus, the number of dead can appear as 13 or 14 depending on the date of the literature examined, and a few use the number 15, often as an approximation. Likewise, the number admitted to hospitals for exposure often varies “1,000” is most often an approximation.

[27] Smithson and Levy, 95. This cites the 85 percent number but Stokes and Bandet use the 74% figure based on Japanese reporting.

[28] Organophosphates, of which sarin is one, are acetylcholinesterase inhibitors. Acetylcholinesterase is an essential component of nerve signal transmission, hence the name “nerve agents.”

[29] Kuzuhito Yokoyama , Shunichi Araki, Katsuyuki Murata, Mariko Nishikitani, Tetsu Okumura, Shinichi Ishimatsu, and Nobukatsu Takusu, “Chronic neurobehavioral and central and autonomic nervous system effects of Tokyo subway sarin poisoning,” Journal of Physiology (Paris) 92 (1998): 317-323.

[30] Ibid.

[31] Several studies looking at long-term exposures noted these problems among victims of the Tokyo sarin attack and 1991 Gulf War veterans exposed to sarin and cyclosarin following the controlled explosion at Khamisiyah, Iraq that contained chemical munitions. See Susan P. Proctor , Kristin J. Heaton, Tim Heeren, and Roberta F. White, “Effects of sarin and cyclosarin exposure during the 1991 Gulf War on neurobehavioral functioning in US army veterans,” NeuroToxicology 27 (2006): 931-939. See also Yokoyama, et al. Several of the researchers involved in both the incident at St. Luke’s and the Yokoyama study have carried out numerous studies on Tokyo victims at varied intervals since the attack to include victims, hospital workers, first responders, and PTSD cases. For a list of these studies, see the Proctor article.

[32] Procter, et al., 318. See also Okumura, et al., “Part 2: Hospital Response” for a more complete description of treatment. St. Luke's gave antidote to moderate and severe cases only, due to limited stock. Mild cases with only minor vision problems received IV’s, oxygen, and observation.

[33] Ibid. The study had a very small sample,

[34] Bowler, et al. These numbers have come under question, and the above studies suggest this issue remains contentious.

[35] Kaplan’s work is a notable exception to this rule. The normally respectable Council on Foreign Relations in 2003 used the number 3,794 for a casualty figure. It appears subsequently as a citation in scholarly articles. Determining their source for that number has been difficult and it is inconsistent with all other figures reported in relation to the attack, both on the high and low sides. That particular figure is anomalous, and may reflect the number of claims filed after the attack to that date (2003), not actual casualties.

[36] This number appeared in several reports and papers from military and military educational institutions, many citing the same dubious source.


Aum Shinrikyo, Part 2: Points of Failure

Aum Shinrikyo, Part 2: Points of Failure

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