Excessive benzene found in NW China tap water (3)

Excessive levels of benzene in tap water have affected more than 2.4 million people in downtown Lanzhou, northwest China's Gansu Province, provincial authorities said on Friday.

Tests on Friday showed tap water contained 160 micrograms of benzene per liter, far in excess the 10 micrograms per liter national limit, according to the city's environmental protection office.

The city government warned citizens not to drink tap water for the next 24 hours. Benzene is a colorless carcinogen used in manufacture of plastics.

Tests on Thursday and Friday found between 118 micrograms to 200 micrograms of benzene per liter, according to Veolia Water, a Sino-French joint venture and the sole water supplier for urban Lanzhou, the provincial capital.

An initial investigation found problems in a 3 km channel which links the plant that preprocesses the water and the plant that supplies water to Lanzhou. Closure of the channel will cut the city's water supply by half, said Tian Hong, head of Lanzhou's water quality monitoring station. Fire engines will be used to carry water to affected areas.

The local government is investigating the source of the contamination, and sources with Veolia told Xinhua that they believed that the benzene came from chemical waste, but refused to single out any particular plant. They denied any possibility that the Yellow River, original source of the water, was polluted. Gansu publicity department reaffirmed on Friday afternoon that the Yellow River, which runs through the city, is not contaminated.

Lanzhou residents panicked upon hearing the news, rushing to supermarkets or community grocery stores to stock up on bottled water. At Hualian Supermarket, one of the largest in downtown Lanzhou, many trolleys or baskets full of cases of bottled water were to be seen. Latecomers gathered in front of empty shelves, waiting for resupply.

"I had no idea what benzene was, but my family are all scared. My husband called to ask me to buy as much bottled water as I can," a shopper told Xinhua.

This is the second incident of its kind in Lanzhou in two months. On March 6, residents reported a strange odor when they turned on their taps, which was later confirmed to be a high concentration of ammonia, but still within the limits of the national standard.