Epidemiological study of sarin poisoning in Matsumoto City, Japan

On the night of June 27, 1994, about 12 liters of sarin were released by terrorists in Matsumoto City, Japan. In order to investigate the epidemic, community-based questionnaire surveys were conducted. The subjects were all inhabitants (2052 people) living and staying in an area of 1050 meters from north to south and 850 meters from east to west including the sarin release site. Participants included 1743 people who answered the questionnaire at the first survey; those with symptoms were contacted for follow-up at four months and one year after the episode. The number of sarin victims were 471 persons. Muscarinic signs were common to all victims; nicotinic signs were only seen in severely affected victims. The geographical distribution of sarin victims was closely related to the direction of the wind. Three weeks after the intoxication, 129 victims still had some symptoms such as dysesthesia of the extremities. At that time, many victims had begun to experience asthenopia, which was even more frequent at four months. Although victims who felt sarin-related symptoms had decreased by a year, some still had symptoms such as asthenopia. Sarin released in a suburban area affected approximately 500 inhabitants living nearby; some still had symptoms a year after the intoxication.