A survey was done on natural radioactivity level and annual effective dose rate of main building materials in Baotou

China.The natural radionuclides of 40K

232Th and 226Ra in main building materials collected from Baotou were measured using NaI γ-ray spectrometry and the measured data were analyzed according to the national standards and radiological protection principles of the European Commission.The specific activities of 40K

232Th and 226Ra in the building materials samples were 218.82 1145.92

19.75 132.50 and 11.46 82.66 Bq/kg

respectively.The internal and external exposure indexes of building materials were 0.06 0.41 and 0.28 0.70

respectively.The annual effective dose equivalent was 0.41 0.97 mSv/y.This justifies the production and sale of the main building materials

as both the internal and external exposure indexes of building materials are less than 1.The effective dose rate of ash brick is 0.97 mSv/y

while the maximum acceptable value is 1 mSv/y.Therefore

it is necessary to control the amount of industrial waste residue in building materials to avoid unnecessary radioactive exposure to residents.