Radioactive material in emissions from coal burning does not significantly affect smog, authorities said on Thursday.

In response to a recent online discussion-that went viral - regarding smog hazards in northern China, environmental authorities clarified that the amount of radioactive material released into the air by coal-burning power plants is minimal and that the widespread conjecture that it was hazardous "lacks scientific basis".

For each gigawatt of electricity coal-fired power plants produce, only about 2.6 per thousand of the radioactivity in the coal is released into the air, an amount unlikely to pose a health hazard, the Ministry of Environmental Protection said in a statement released on Thursday.

The ministry based its conclusion on monitoring data of the natural radionuclide content in 24 provinces and measurements taken from 563 coal samples, the statement said.

"Most of the radioactive material is left in the filters in coal-fired power plants. Only a very limited amount of waste, about 1 to 2 percent, can escape into the air," said Xie Qiuju, a professor and expert on radiation protection at the Peking University School of Physics.

Responding to the claim that radiation levels of coal near the world's biggest uranium mine in Daying, the Inner Mongolia autonomous region, are much higher than in other coal, the statement said that coal samples collected near the mine had 6.3 to 57.7 becquerels of uranium-238 per kilogram, about the same level as coal elsewhere.

The coal located 100 meters beneath the uranium mine has yet to be developed, said the statement.

Even in the case of coal with radioactive content being burned in coal-fired power plants, the likelihood of uranium entering into the air is "rather minimal", Xie said.

Atmospheric radioactive levels remain stable, and no abnormal changes have been found, the statement said. Real-time data on radioactivity levels nationwide can be found on the ministry's website.

On Jan 1, the ministry started to release five-day air quality forecasts in key areas, provinces (autonomous regions and municipalities), providing information on air quality, primary pollutants, and the health effects.

wangyanfei@chinadaily.com.cn