(Autumn 1995) A chemical weapon attack against Tokyo subway passengers on 20 March 1995 killed 12 persons and injured approximately 5,500 others. It is believed that in June, 1994, a similar attack occurred in a residential area in central Japan, killing seven persons and making more than 200 others ill. Isopropyl methyl-phosphonofluoridate, sarin, is first attributed to chemists in Nazi Germany in the 1930's. Referred to as nerve agent (GB) in chemical weapons (CW) parlance, sarin is also described as "the poor man's atomic bomb". GB was not developed as a nerve agent by the Nazi's until 1944 and was not employed as a chemical weapon until long after World War II had ended.
Sarin acts on the human nervous system by inhibiting the enzyme cholinesterase (CHE), lowering the pulse rate and oxygenation, and increasing the excretion of mucus. A doctor who diagnosed a Tokyo subway attack patient reported that he had difficulty breathing, contraction of his eye pupils, decline in blood pressure and decline in the level of cholinesterase (CHE) in his blood to a quarter of its normal level. Symptoms in patients treated at the hospital for inhalation appeared to worsen with time. Victim-survivors of the Tokyo subway exposure said they started feeling pain in their eyes immediately after seeing liquid seeping from the sarin delivery devices. All experienced tunnel vision, breathing difficulties, nausea, and sore throats. For sarin exposure survivors, it takes months for CHE levels to return to normal and there is risk of long-term damage to eyes, lungs, and digestive systems. In those who were killed in the subway attack, the cause of death was either respiratory failure or cardiac arrest from the struggle to breathe as they choked on their own mucus and saliva.
Most of the readily available CW literature addresses sarin categorically along with other nerve agents and from the perspective of militarily significant production and weaponization quantities. Although production techniques for major chemical weapon agents involve some specialized process steps, detailed examples can be found in open literature and follow from standard chemical engineering principles. Sarin cannot be spontaneously produced by natural causes. Achieving end-formulation of sarin under laboratory conditions is possible via more than one route, but the somewhat complicated processes involved are exacerbated by handling problems. Accidental exposures are recorded even among military production and weaponization experts.
Synthesis of nerve agents includes some difficult processes involving highly corrosive or reactive materials. For a sophisticated production facility to make militarily significant quantities of one class of nerve agents might cost between five and twenty million dollars, although dispensing with modern waste handling facilities might cut the cost in half. The plant designer might provide ventilated buildings with airtight areas operated at negative pressure and some reactors constructed for entirely remote operation. This is a common practice for civilian commercial chemical plants in many technically developed countries; it requires a major installation of piping and instrumentation with computer controls.
Some of the equipment needed may have distinctive features, such as corrosion-resistant reactors and pipes and special ventilation and waste handling equipment, but these can be dispensed with by relaxing worker safety and environmental standards and by replacing hardware as it corrodes. Moreover, production is easier if a proliferant is willing to cut corners on shelf-life, seeking only to produce low-quality agents for immediate use. In general, commercial pesticide plants are well suited for agent production; they have the precursor chemicals (materials from which chemical agents are synthesized), equipment, facilities, and safety procedures required for nerve-agent production. Chemical-warfare agents can be produced through a wide variety of alternative methods, but relatively few are suitable for large scale production.
Once produced, sarin presents both a storage and delivery problem. In the 1950's and 1960's, military chemical weapons specialists conceived of the binary munitions concept to ameliorate these problems. Binary munitions contain two relatively non-toxic chemical components which are mixed during flight to their targets to produce standard nerve agents. Militarily, the production of a nerve agent is several steps removed from an operational chemical weapon capability. The latter requires design and development of effective munitions, filling the munitions before use, and mating them with a suitable delivery system. In the filling process itself, the agents must be transferred from a storage vessel to the munitions, and the munitions must be sealed, without any vapor loss and especially without spillage from the transfer hose. Special equipment and procedures to detect and locate leaks are needed both in the filling area and in the area where the munitions are stored.
Some passengers said a man wearing a sanitary mask got on the forward car of their subway train at the rear door and, after taking a seat, he soon removed a box wrapped in newspaper from a briefcase. He then stood up and placed the parcel at his feet while he leisurely read a newspaper. Leaving the package behind, the man got off at the next station and a puddle of liquid began to form around the newspaper.
Since the Tokyo subway attack, Japanese authorities have conducted extensive search and seizure operations against facilities of the Aum Shinrikyo religious sect suspected as the perpetrators. Some of the facilities raided were found to be chemical laboratories. Massive quantities -- amounting to several tens of tons in weight -- of more than 30 kinds of chemicals seized included phosphorus trichloride, sodium fluoride, isopropanol, sodium cyanide, sulfuric acid, glycerin, and phenyl acetonitrile, some of which are used in sarin production. Police also found some 160 drums of peptone, a substance used in bacteria cultivation, suggesting a possibility that the cult was conducting bacteriological research. Huge volumes of chemicals had been purchased by front companies that had thinly-disguised ties to the sect.
The Buddhist sect was founded in 1987 by Chizuo Matsumoto, alias Shoko Asahara. The group has its headquarters in central Japan with 19 branches throughout the country. The doctrines of Aum Shinrikyo are based on ancient yoga and primitive Buddhism, and require worshipping the Hindu God Siva, believed to preside over both destruction and creation. Destruction has been elevated by the cult and is viewed as on par with creation. The sect has tried to build its own "kingdom" within its controlled compound facilities by establishing ministries and agencies under Asahara, its paramount leader. Among these, the sect "Science and Technology Agency" consists of scientists who graduated from prestigious universities in Japan. It is divided into several teams specialized in chemistry, biology, physics and medicine.
Investigators attach significance to the possibility of producing sarin with chemicals seized from the sect. The first sarin incident occurred right after massive purchases of chemicals by sect front companies. By-products of the sarin production process were detected near sect facilities in July 1994 shortly after the second incident. People who have left the sect have charged that it administered chemical substances to its followers to induce a meditative state during religious training. Barbituric acid drugs found in sect facilities produce hypnotic effects. Analysis of chemicals confiscated during raids raises a suspicion that, in addition to sarin, the group tried to produce tabun -- o-ethyl n-dimethylphosphoramidocyanidate (GA) -- another highly toxic chemical weapon.
Following the Tokyo subway attack, Japanese authorities discovered there was an absence of domestic legislation to control the manufacture, possession, and use of chemical weapons. The Japanese parliament has been engaged in rapid enactment of appropriate laws. The incident also added new stimulus for expeditious Japanese ratification of the Chemical Weapons Convention (CWC).