Only 24 percent of groundwater in the North China Plain is safe to drink, a recent study by the China Geological Survey shows.

The four-year study found groundwater in the area has been tainted by heavy metals, chemical fertilizers and surface water pollution caused by leaks from garbage dumps and sewage water irrigation.

Zhang Zhaoji, a hydrogeology expert at the institute of hydrogeology and environmental geology under the Chinese Academy of Geological Sciences, said on Wednesday at the 12th annual meeting of the China Association for Science and Technology in Fuzhou, Fujian province, that the inferior quality of groundwater is damaging people's health and creating conflicts over the supply and demand for water.

Most of the shallow groundwater in the plain is polluted to some extent, though the quality of the deep groundwater is relatively good, according to the study.

The study said more than 75 percent of groundwater in the North China Plain is not safe to drink without being properly purified.

An earlier seven-year study by the Ministry of Environmental Protection on groundwater in 118 cities found 64 percent of them had groundwater that had been polluted, 33 percent was lightly polluted and 3 percent had access to a clean supply of groundwater.

Some environment experts have said the figure is conservative and estimated that 90 percent of China's groundwater is polluted.

In September, a draft plan for national groundwater protection from 2010 to 2020 was reviewed and passed by the ministry and will be submitted to the State Council for consideration and approval.

The draft plan aims to alleviate the pollution of groundwater in populated areas and put in place a national prevention and treatment system for polluted groundwater by 2020.

While acknowledging the government's efforts, many environmental experts said they remain concerned about the long-term damage polluted groundwater posed to people's health, as well as about the water supply itself.

Ma Jun, director of the Beijing-based Institute of Public and Environmental Affairs, said it is difficult to filter out pollutants like heavy metals. Once the water has been polluted, he said it could possibly take thousands of years for the situation to be put right.

According to the Ministry of Health's Key Endemic Disease Control Program (2004-2010), there are approximately 39 million people across the country who suffer from dental discoloration or fluorosis as a result of having received too much fluoride in water during their developmental years and nearly 3 million people suffer from the bone disease skeletal fluorosis as a result of the same cause.