Initial test results show that the levels of styrene in the contaminated water were 1.3 - 3.6 times higher than normal, which can potentially negatively affect people’s health.

Black waste oil flows to the upstream of Da river’s water. Photo: TTT 

Chairman of the Hanoi People's Committee Nguyen Duc Chung confirmed on October 15 that tap water across the south-east region of the city is contaminated with styrene, a carcinogenic substance, due to an oil contamination at the source, local media reported.

Since October 10 afternoon, residents in some districts of the capital city have encountered polluted water supplies, with many reporting a smell similar to burning plastic coming from their tap water, and have thus turned to bottled water.

Chung informed that the water was contaminated and the abnormal smell detected in tap water was caused by a significant amount of used oil discharged into the Da river upstream, one of the sources of water supply for residents of the capital city.

Initial test results show that the levels of styrene in the contaminated water were 1.3 - 3.6 times higher than normal, which can potentially negatively affect people’s health.

According to Chung, Vinaconex Water Supply Joint Stock Company (Viwasupco), which purifies water from the Da river and supplies for Hanoi, was aware of the problem even before the people of Hanoi began to detect the strange smell, but failed to alert officials and took no action to stop the oil from flowing into the water plant and continued to supply water for Hanoi.

"We will handle this case seriously," Chung said, adding that Hanoi’s authority will send a letter to Hoa Binh province’s Police to investigate Viwasupco’s responsibilities.

“We have worked with the company and required the apartment buildings and water stations to discharge the contaminated water. Viwasupco must pay the cleanup cost and needs to take responsibility,” Chung stressed.

Hanoi's authority recommended Viwasupco to set up cameras to supervise the entire process of water purification and change technology to improve water quality, Chung stated.

Water provided by Viwasupco unsafe to drink

The warning followed a finding that the water, contaminated by used oil, contained high levels of styrene, a substance that is probably carcinogenic. 

People can use the water for other purposes like washing clothes and bathing, but should not drink or use it for cooking, authorities said at a press conference on October 15.

Nguyen Van Ton, Viwasupco’s director, said on October 14 that the water it supplies to Hanoi "meets standards" and "contains no toxin" despite oil contamination warnings.

He said a test performed by the company revealed that the contaminated water was within safety standards set by the Ministry of Health.

However, Ton did not make clear if the used oil already polluted the water which is supplied to Hanoi residents. 

At that meeting with the media, regarding reports saying hundreds of thousands of families in Hanoi said their tap water smelled unpleasant and was unusable, Ton said the smell was probably due to the chlorine in the water, since the company had increased its amount to deal with the oil contamination.

He also said that bad smell was a "subjective perception," adding that the source of the smell would be announced by the authorities in the future.

Daily life of thousands of people in the capital city has been badly disrupted by contaminated tap water.  The foul smell lingered for days, prompting residents to stop using the tap water for cooking and daily activities and buy bottled water instead for consumption.