The Tainan City Government began an operation on Thursday to clean up dioxin-contaminated soil around the site of the defunct Anshun factory of the Taiwan Alkali Industrial Corp (TAIC,
The NT$3 million (US$93,000) operation, expected to be finished before Feb. 6, will excavate 180m3 of polluted soil from areas along the former chemical factory's drainage system. The pollutants will be sealed in a concrete structure for the next 20 years, officials from the city government's Environmental Protection Bureau said.
The officials said stockpiles of pentachlorophenol -- a chemical used as a wood preservative and pesticide and produced by the factory -- had been washed into the drainage system by rain over a long period and had leached into the surrounding soil, causing the dioxin concentrations in the soil to exceed the highest allowed limit by 64,100 times, with the pentachlorophenol level 257 times higher than the tolerable limit.
In November 2001, Taiwan adopted 1,000 nanograms of international toxic equivalents (TEQ) per kilogram as the maximum acceptable level of dioxin concentration in residential soil. This standard has also been adopted in the US, Germany and Japan.
Dioxins are known carcinogens that can cause birth defects, diabetes, immune system abnormalities and many other adverse health effects if they accumulate in the body in large amounts.
Research shows 200 parts per trillion TEQ dioxin level in residential soil corresponds to a one-in-10,000 cancer risk.
The Anshun factory was set up by the Japanese in 1942 to produce a variety of chemical products, including hydrochloric acid, caustic soda and liquid chlorine. The factory became a state-owned company named Taiwan Alkali the year after Japan's surrender at the end of World War II in 1945.
CPC Corp, Taiwan (CPC,
For decades, residents living around the factory grew farm produce and raised fish in ponds without any knowledge of the pollution hazard.
Recently declassified government documents show that the government took no action after becoming aware in 1982 that mercury concentrations in the area's fish exceeded levels considered safe for human consumption.
At the request of the Tainan City Government, National Cheng Kung University researchers tested blood samples from 570 residents living in the polluted area. Testing results showed that 72 percent of them had much higher levels of dioxins in their blood than the tolerance limit set by the UN.
The Environmental Protection Agency has spent more than NT$110 million since 2003 to remove contamination sources and monitor soil conditions and water quality in fish ponds around the site. In 2005, the Ministry of Economic Affairs set aside NT$1.3 billion over five years to help the affected residents.