GUANGZHOU: A tributary of the Pearl River in South China's Guangdong Province is heavily polluted with a toxic chemical, the authorities revealed yesterday.

According to a government news release, the cadmium content was 10 times above the safety level in the Gaoqiao section of the Beijiang River in Shaoguan on Tuesday.

The government said that Shaoguan Smelting Plant had spilt an unspecified amount of cadmium into the river during production.

The smelting plant was ordered to shut its drainage pipe on Sunday after the pollution.

But the government did not say how fast the contaminated slick was flowing and how long the water would be polluted.

Cadmium is an extremely toxic metal, said Zhang Gan, a professor at Guangzhou Institute of Geochemistry under the Chinese Academy of Sciences.

Most cadmium is extracted during the production of other metals like zinc, lead, and copper. It does not corrode easily and has many uses, including in batteries, pigments, metal coatings and plastics.

"Drinking water with excessive cadmium may damage the central nervous system, or even cause cancer," Zhang told China Daily yesterday.

As the cadmium dissolves in the large amount of clean water discharged from the upstream area, the water quality in Beijiang can be expected to return to normal soon, he said.

The government has announced that it would discharge more than 700 million cubic metres of water from Nanshui Reservoir in Shaoguan, and said the diluted water would be safe to drink.

To ensure water safety in the lower reaches of the river, the provincial government yesterday ordered Guangzhou and Foshan cities to activate emergency response schemes.

Environmental protection departments have also asked 20 water testing stations in Shaoguan, Yingde and Qingyuan along the river to monitor the slick.

The local government in Yingde stopped water supply to one district for several hours on Tuesday, but supply was normal in the other three districts.

Also on Tuesday, Zhang Lijun, deputy director of the State Environmental Protection Administration, arrived in Yingde a city with 100,000 residents downstream of Shaoguan to inspect the situation.

It is the second major water pollution China has suffered in less than two months.

On November 13, a chemical plant blast caused the leakage of 100 tons of benzene and its derivatives into the Songhua River in Northeast China, forcing cities along the river to suspend water supply for days.

Chinese workers are working round the clock to build a dam to reduce the impact of the water pollution on the neighbouring Russian city of Khabarovsk.

(China Daily 12/22/2005 page1)