Lessons from Minamata mercury pollution, Japan - After a continuous 22 years of observation

One of the most visible tragedies by industrial water pollution is Minamata disease, methylmercury poisoning caused by eating contaminated fish, which has killed more than 100 people and paralyzed several thousand people arou nd Minamata Bay, Japan and the adjacent Yatsushiro Sea since 1956. The caus e of Minamata disease was confirmed, not by analyzing environmental samples such as sediments (containing more than 600 ppm of Hg) or fish (at least 2 0 ppm) at the bay, but by symptoms of Minamata disease patients that resemb led previous mercury poisoning reported in a European medical journal. Merc ury dispersion was traced for 22 years to collect mercury concentration mea surements in Yatsushiro Sea surface sediments at 24 fixed stations. The ana lytical results of mercury revealed four trends of mercury movement from th e bay: 1) a rapid increase in Hg concentrations up to 1984; 2) a dramatic d ecrease in mercury concentrations after an artificial mercury decontaminati on project began in 1984: 3) a strange drop in mercury contents due to an h istorical rainfall in the region in 1982 and; 4) natural decontamination, w hich has been underway since 1985. The tragedy at Minamata has provided man y lessons which have shaped the scientific field in environmental research, especially in the area of water quality. (C) 1998 Published by Elsevier Sc ience Ltd. All rights reserved.