Whatever is not decomposed, accumulates. In case of a metal, it is a basic mate
rial, so it doesn't get decomposed, and of course, if you should discharge it f
rom your body, then that's okay. But once something gets into your body and it
cannot be decomposed, it will accumulate in the body, and over the years you wi
ll get increased levels of concentration. This is a very big and crucial proble
m. Even if the concentration in the water were low, this would still cause bigg
er problems at the top of the food chain, because as you go higher in the food
chain ladder, the larger the level of accumulation.
The third item I would like to talk about is volatile organic chemicals. In 198
0, in Silicon Valley in the United States, there was a discovery of too many in
stances of leukemia and abnormalities in babies. It was found that there was a
great amount of organic solvent discharged from a plant that was dissolving int
o the ground water. The organic solvent discharged from the plant was actually
being accumulated in an underground tank, but there was a leak in the undergrou
nd tank, thus polluting the underground water. This sewage got dissolved in the
water, and this became a big controversy in the United States. We in Japan had
had the Minamata Disease and the Itai-Itai Disease, where such pollu-tion caus
ed problems and diseases. And so we were very sensitive about these issues, and
we immediately went looking into similar situations in Japan. We then found an
instance of ground water pollution near the plants which were producing semico
nductors. And the first report was by a plant located in Taishi City in Hyogo P
refecture.
This is a different semiconductor plant, and when the level of production was l
ow, the recovery rate was fairly high (see Figure 11). However, as the producti
on went up, the recovery rate went down. That is to say, the gap between the pr
oduction and the recovery rate shows the amount of disappearance, but where has
it disappeared? We have to ask the question, where has it gone? Up until this
time, organic solvents were said to be vola-tile and would be discharged into t
he air, and therefore be treated very naturally and would not cause any problem
s. And nobody paid any attention to that.
