the cause of the Minamata Disease. However, this was not offlclally recognized, and that is the reason why the relevant factories contlnued to drain mercury a s waste.

And in 1965, just nlne years after Minamata, the Minamata Disease was identifie d for the first time at the Agano River in Niigata Prefecture, far away from Mi namata. Then, finally, in 1968, the Japanese Mlnistry of Health and Welfare off iclally recognized that methyl mercury was indeed the cause of the Minamata Dis ease, and regulated the factories to stop the production of the relevant produc ts. In other words, it took twelve years for the govern-ment to offlcially reco gnize the cause and ban the production in the relevant factories.

Let me refer to the example of the Agano River in Niigata Prefecture. When the Mlnamuta Disease was initially experienced, the cause was identified through tr ial and error. When the Minamata Disease was detected in Agano Rlver In 1965, w e already had certain preliminary researches and surveys in Minamata. That is w hy once we experienccd thc Minamata Dis-CLISC in the Agano River, we could cond uct a more clear-cut investigation. Wc wlsh that the total ban of production wo uld have been implemented prior to 1963, thus not to havc a repetition in the M inamata Disease In Agano River.

There was the factory In the upstream produclng the acetaldehyde, which drained and vcsted the methyl mercury in the river. Then along the river, thcse circle s are the loca-iions of thc Minamata Dlsease patients (see Figure 8). And you w ould find the number of patients increasing towards the downstream.

The concentration of the mercury in the water was not high. So even if you drin k the wa-ter. the concentration was very low, not to cause the disease. Still, mercury was accumu-lated in the human body to cause the Minamata Disease. Let m e elaborate. That was the