Public Health

Exposure To Sarin Causes Delayed Effect On Postural Balance

TOKYO, Apr 24 (Reuters) - The authors of a preliminary study conducted in
Japan report that exposure to sarin may result in delayed
vestibulocerebellar effects on balance.

On March 20, 1995, approximately 5,500 people were exposed to sarin, which is a potent acetylcholinesterase inhibitor, during a terrorist attack on a Tokyo subway.

Dr. Kazuhito Yokoyama, of the University of Tokyo and a multicenter Tokyo
team, present data on the long-term effects of sarin on postural balance in 9 men and 9 women who were exposed to the chemical during that subway incident.

Six to eight months after the incident, the researchers used computerized
posturography to measure balance in the subjects. Their findings are
published in the January issue of the Journal of Occupational and
Environmental Medicine.

Initial plasma cholinesterase levels on the day of the poisoning ranged from 13 to 95 IU/l, and the figures did not vary significantly by gender, Dr. Yokoyama's team said.

"[P]ostural sway...in the anterior-posterior direction and area of sway with eyes open was significantly larger in the cases than in [a group of healthy] controls." And "...low-frequency sway in the anterior-posterior direction for [women] and low-frequency sway and length of sway in the medio-lateral direction for [men] were significantly related to..." exposure to the agent, Dr. Yokoyama's group found.

The researchers stressed that the delayed vestibulocerebellar effects and a number of other effects of sarin poisoning proved to be subclinical. Dr.
Yokoyama's group pointed out that neuroimaging and other testing on the
brains of the poisoned victims "...should have been performed..."
immediately after the attack.

J Occup Environ Med 1998;40:17-21.

by Sandra Katzman