"Extremely low levels" of radioactive iodine have been detected in the air around more Chinese areas, including Shanghai and Tianjin, but the materials pose no threat to public health.

The information was included in a statement issued Wednesday by China's National Nuclear Emergency Coordination Committee.

Low levels of radioactive isotope iodine-131 were detected on Wednesday in 18 provinces, municipalities and autonomous regions: Shanghai, Tianjin, Chongqing, Hebei, Shanxi, Inner Mongolia, Jilin, Heilongjiang, Jiangsu, Anhui, Zhejiang, Fujian, Henan, Guangdong, Guangxi, Sichuan, Shaanxi and Ningxia, said the statement.

The material is believed to have drifted to China by air from the quake-damaged Fukushima Daiichi Nuclear Power Plant in Japan.

However, the amount of radiation these materials have were below one-hundred-thousandth of the average annual exposure level to natural radioactive sources such as rocks, soil, food and the sun, the committee said.

According to the statement, the radiation levels of the materials detected in the country are equal to levels of radiation from cosmic rays a person could be exposed to if traveling for 2,000 kilometers in a plane.

No protective measures need to be taken against contamination from the material, said the statement.

The committee's conclusion was based on monitoring and analysis results from the Beijing-based Regional Specialized Meteorological Center affiliated with the World Meteorological Organization and the International Atomic Energy Agency, the State Oceanic Administration and the Ministry of Environmental Protection, according to the statement.

Low levels of radioactive isotope iodine-131 from Japan's quake-damaged nuclear power plant were first detected in China in the northeastern Heilongjiang Province over the weekend.