Sewage has become one of the biggest threats to China's marine environment, with more than half of the wastewater pumped into the sea untreated, China Daily reported, citing a United Nations Environment Programme report released in Beijing Wednesday. Results from the country's 200 coastal monitoring stations indicated that more than 317 billion tons of wastewater, both treated and untreated, were discharged from the mainland in 2005, almost twice as much as in 2000. China has promised to treat about 70% of its urban wastewater in the next five years and decrease pollutants by 10%. There are currently 145 wastewater treatment plants under construction in coastal areas. Zhou Shengxian, head of the State Environmental Protection Administration said measures to clean up the environment will focus on the Bohai Bay, the Yangtze River estuary and the lower reaches of the Pearl River delta.