Public exposure to natural radioactivity and radon exhalation rate in construction materials used within Greater Accra Region of Ghana

Abstract

The natural radioactivity of 238U, 232Th, 40K, radiological hazards and 222Rn exhalation rate in building materials used within Greater Accra Region of Ghana, have been measured using Gamma spectrometry and CR-39. The results obtained are as follows 238U (2.6–47.1 Bq/kg), 232Th (3.6–43.0 Bq/kg), 40K (62.8–1222.2 Bq/kg), radium equivalent (32.7–174.3 Bq/kg), internal hazard index (0.04–0.51), external hazard index (0.04–0.23), activity concentration index (0.10–0.63 mSv/y) absorbed dose rate (9.5–76.3 nGy/h), outdoor effective doses (11.6–93.6 μSv/y), indoor effective doses (46.5–374.1 μSv/y,) and excess lifetime cancer risk (0.04 × 10−3–0.33 × 10−3). 222Rn exhalation rate (3.1 × 10−5–11.4 × 10−5 Bq/m2 h), 222Rn activity (17.4–42.6 Bq/m3), effective radium (0.19–0.64 Bq/kg). Positive correlation was found between 238U and 222Rn. The results were discussed in terms of limits to the accepted natural radioactivity levels and compared with similar studies reported in other countries. The gneiss rocks recorded excess lifetime cancer risk values of (0.32 × 10−3 and 0.33 × 10−3) greater than the world value of 0.29 × 10−3 proposed by UNSCEAR, 2000. With exception gneiss rocks from Shai hills which recorded high value of cancer risk as compare to the world average value, all the studied building materials do not pose any radiological effects to the people of Greater Accra Region when used for construction. Keywords: HPGe, CR-39, 222Rn, NORMS, Construction materials