Levels of lead in the Danjiangkou reservoir supplying water to Beijing and other cities in Northern China were 20 times the maximum safe level set by the World Health Organization between 2007 and 2010, South China Morning Post reported, citing research published by Chinese scientists.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–though it did not say whether the problem still exists.