Fifteen sources of nuclear radiation exposed by China's earthquake last week remain inaccessible, and China faces a "daunting challenge" to prevent environmental contamination across the disaster zone, a senior official said Friday.
Wu Xiaoqing, China's vice minister for environmental protection, reassured reporters that there had been no leak of radioactive substances into the environment.
He said 50 sources of radiation had been buried by debris from the massive earthquake in central China, and that 35 of those had been secured. The rest lay buried or located but unreachable under the debris of collapsed buildings.
He did not specify what the radiation sources were.
Foreign experts have said the radioactive sources likely came from materials used in hospitals, factories or in research, not for weapons.
Wu cautioned that a number of other "hidden" sources of pollution could arise as workers begin digging into the rubble of numerous factories and refineries.
U.S. State Department spokesman Tom Casey told reporters that Washington was not aware of any threat to humans, "but obviously it is a concern."
He added that many of the locations were remote and that the U.S. was relying on the Chinese government for much of its information.
The worst-hit areas in Sichuan province include many high-risk petrochemical and chemical companies, Wu said. Around three-fourths of the more than 100 chemical plants in the quake-hit area were forced to stop production as a result of damage, he said.
No environmental damage has so far been recorded, but as factories resume production officials must ensure that any chemical waste uncovered is properly disposed of, he said.
"We now face more daunting challenges in investigating and removing hidden troubles and carrying out environmental inspections," he said.
China's environment ministry was upgraded earlier this year in an attempt to give it more clout over factories and local governments that could ignore attempts to inspect their environmental record.
Factories should not resume production unless they have been inspected by environmental agencies and all sources of pollution have been removed, Wu said. Reconstruction can only proceed after environmental impact assessments have been carried out.
"We have to supervise those companies to make sure they resume their water pollution control as soon as possible," he said.
Seismological experts should also be consulted when assessing the environmental risk those companies pose, he said.
