Beijing drinking water reservoir had lead levels ‘20 times WHO standard’ for at least three years
A major reservoir supplying drinking water to Beijing and other cities in northern China contained heavy metal pollutants at levels far above safe standards for a period of at least three years, according to a study by Chinese scientists.
Levels of lead in the Danjiangkou reservoir were 20 times the maximum safe level set by the World Health Organisation, at more than 200 micrograms per litre, between 2007 and 2010, the research found, though it did not say whether the problem still exists.
The WHO standard for a safe level of lead in a surface water source is 10 micrograms per litre. The maximum level regarded as safe by the United States Environmental Protection Agency is 15 micrograms. China's own national surface water quality standards call for levels to remain under 50 micrograms.
The study, published in the peer reviewed Journal of Environmental Informatics, found that levels of lead in the reservoir, which supplies more than 60 per cent of taps in Beijing, increased 20-fold in the three-year period.
Professor Zhang Quanfa, a researcher with the Chinese Academy of Sciences’ Wuhan Botanical Garden and lead scientist of the project, declined an interview due to the sensitivity of the issue.
Whether the water from Danjiangkou reservoir was still drinkable “was not a question I am able to answer,” he told the South China Morning Post.
The Beijing Water Authority and the Water Quality Monitoring Centre of the Beijing Water Group declined to comment on the research.
The Beijing government has previously said that water from Danjiangkou receives extensive treatment at processing plants before it reaches individual households, so the quality of water in the reservoir does not necessarily reflect the quality in household taps.
The Ministry of Water Resources said last month that the reservoir had been rated Grade 1, meaning lead levels were below 10 micrograms per litre, for more than 70 per cent of the time it has been in use. Lead levels in the reservoir have never fallen below Grade 2 on the national standards, between 10 and 50 micrograms per litre, the ministry said.
Excessive lead in drinking water can lead to a host of health problems, and can be especially dangerous to infants and children, according to the US EPA.
Lead poisoning can cause delays in physical or mental development with detectable deficits in attention span and learning abilities in children, while in adults the symptoms include kidney problems and increased blood pressure.
Earlier this week researchers in Hong Kong found excessive levels of lead in the drinking water of some public housing estates, with suspicion falling on building materials used.
The mainland study found other kinds of pollutants in Danjiangkou water that exceeded safety standards, including arsenic and chromium, which can lead to cancer and skin problems.
The reservoir held 29 billion tons of water at the end of 2014 and had a surface area of around 450 square kilometres. Its dam was 0.8 km downstream of the junction of the Han and Dan rivers in Hubei and Henan provinces.
“Greater efforts must be made to reduce nitrogen, arsenic and lead pollution for water conservation in the reservoir,” the researchers said in their paper.
They said the increased levels of lead may be caused by an increase in vehicle exhaust pollutants in the upper Han river basin area, as well as mining related activities.
The reservoir is a key part of China’s ambitious South-North Water Transfer Project, which is designed to funnel more than 14 billion tons of water per year from the Yangtze River region to more than 20 cities in the dry north, with Beijing's water supply given top priority.
By the end of last year the government had spent more than 200 billion yuan on the project with the main canal exceeding 1,400 km in length.
Other studies have also shown high levels of pollution in the Danjiangkou reservoir, mainly from untreated sewage in the rivers that flow into it.