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  1. IMPACT ON THE ENVIRONMENT
  1. GEO-POLLUTION BY TETRACHLOROETHYLENE

Geo-pollution from Cleaners

There have been a number of cases reported lately of soil pollution by chlorinated organic compounds like tetrachloroethylene. Chlorinated organic compounds are an inevitable substance in many industries to wash parts. Tetrachloroethylene, being heavier than water, low in viscosity and volatile, easily infiltrates deep into the ground, contaminating the soil. It also pollutes subsurface air in this process, and the air comes up to the ground surface to cause serious health problems for people. The substance also goes down deeper to reach and contaminate ground water. The pollution then further spreads along with the flow of the ground water. At this point, the purification works have become very difficult.

Many cleaners collapsed in the Hanshin Earthquake and let chlorinated organic compounds, tetrachloroethylene, flow out causing pollution.

A research group conducted a geo-pollution investigation on cleaners throughout Kobe city (Earthquake Geo-pollution due to the 1995 Hyougoken Nanbu Earthquake, the Committee of Environmental Geology, Geological Society of Japan, 1995). According to the result, 55 out of 377 cleaners were found to have caused soil contamination. In the worst case, the tetrachloroethylene concentration reached 3,900 times of the environmental quality standards. The author also joined the investigation in Nada-ward to find a critical situation that 35 out of 60 cleaners were damaged by the disaster, including 11 that had caused contamination (Tainosho et al, 1995). The tetrachloroethylene concentration was over 90 ppm in three cases, including the highest with 200 ppm.

Reconstruction works have already been under way in the polluted areas leaving the contaminated soil as it is. Purification works should have been carried out by municipalities at public expense. Unfortunately, the law concerning soil contamination is not satisfactory, which must have been one of the reasons for the delay in taking countermeasures.

(TAINOSHO Yoshiaki)