Effects of sarin on the nervous system in rescue team staff members and police officers 3 years after the Tokyo subway sarin attack. (Articles).

Although the clinical manifestations of acute sarin poisoning have been reported in detail, no comprehensive study of the chronic physical and psychiatric effects of acute sarin poisoning has been carried out. To clarify the chronic effects of sarin on the nervous system, a cross-sectional epidemiologic study was conducted 3 years after the Tokyo subway sarin attack. Subjects consisted of the rescue team staff members and police officers who had worked at the disaster site. Subjects consisted of 56 male exposed subjects and 52 referent subjects matched for age and occupation. A neurobehavioral test, stabilometry, and measurement of vibration perception thresholds were performed, as well as psychometric tests to assess traumatic stress symptoms. The exposed group performed less well in the backward digit span test than the referent group in a dose-effect manner. This result was the same after controlling for possible confounding factors and was independent of traumatic stress symptoms. In other tests of memory function, except for the Benton visual retention test (mean correct answers), effects related to exposure were also suggested, although they were not statistically significant. In contrast, the dose-effect relationships observed in the neurobehavioral tests (psychomotor function) were unclear. None of the stabilometry and vibration perception threshold parameters had any relation to exposure. Our findings suggest the chronic decline of memory function 2 years and 10 months to 3 years and 9 months after exposure to sarin in the Tokyo subway attack, and further study is needed. Key words: cross-sectional study, neurotoxicity, police officers, rescue workers, sarin. Environ Health Perspect 109:1169-1173 (2001). [Online 6 November 2001] http:// ehpnet1.niehs.nih.gov/docs/2001/109p1169-1173nishiwaki/abstract.html

On 20 March 1995, more than 5,500 people required emergency medical care after a sarin attack in the subways of Tokyo, and 12 people were killed. Although there was a similar sarin attack in Matsumoto City, Nagano Prefecture, Japan, in 1994, far more people suffered from poisoning in the subway sarin disaster in Tokyo than in the Matsumoto sarin attack.

Sarin is an organophosphate cholinesterase inhibitor and has been used as a strong military nerve gas. Recent reports suggest, however, that victims in the Tokyo subway sarin attack were exposed not only to sarin, but also to other by-products generated during sarin synthesis (1,2). Although the clinical manifestations of acute sarin poisoning have been reported in detail (3-9), no comprehensive study of the chronic physical and psychiatric effects of acute sarin poisoning has been carried out. Therefore, an epidemiologic study is needed to investigate the chronic effects of sarin poisoning. However, for the results of such an epidemiologic study to be valid, it must include subjects with homologous backgrounds. Thus, subway passengers who were victims of the disaster are inappropriate for the study because they are so varied in their backgrounds with regard to occupation, socioeconomic status, and educational level.

The rescue team members and police officers who were dispatched to the disaster were also exposed to sarin, primarily or secondarily. Therefore, to clarify the chronic physical and psychiatric effects of sarin, a cross-sectional epidemiologic study was conducted 2 years and 10 months to 3 years and 9 months after the sarin attack on the rescue team staff members and police officers involved in the disaster. In this paper we present the chronic effects of sarin poisoning on the central nervous system, on equilibrium, and on vibratory sensations in relation to traumatic stress symptoms.

Materials and Methods

Study design and study subjects. Fifty-seven study subjects were exposed to sarin, including 27 male rescue team staff members of the Tokyo Fire Department and 30 police officers of the Metropolitan Police Department. In each office of each department, rough matching by age took place, and 52 subjects without exposure, including 29 male rescue team staff members and 23 police officers were selected. After excluding one subject with amnesia not related to sarin exposure, the study population used for analysis consisted of 56 exposed subjects (exposed group) and 52 referent subjects (referent group). Written, informed consent was obtained from all subjects after fully explaining the study procedures.

To assess the dose-effect relationship, it was desirable to divide the subjects into groups according to their level of exposure, creating a high-exposed and low-exposed group. Because it was impossible to exactly estimate the exposure level of each subject, we assigned the subjects who had been hospitalized immediately after poisoning to a high-exposed group, and those who attended hospitals as outpatients to a low-exposed group, based on the description in the self-administered questionnaire. We checked the self-administered questionnaire, excluded two subjects who did not provide any information about their hospitalization, and assigned 25 subjects to the high-exposed group and 29 to the low-exposed group. Further, we classified the high-exposed subjects into two groups, namely, those who lost consciousness or ...