Assessment of Natural Radioactivity and Radon indoors in the New Campus of the Princess Nora University and the Associated Health Hazards

Abstract

Surveillance monitoring in the new campus of Princess Nora University has been carried out to ensure that the radiation doses received to the public are below the authorized limits, as well as providing a base-line data on background radiation inside the campus. Soil and tap water samples were collected from selected locations in the campus, and indoor radon was measured in three selected buildings through its daughter Po-218, with a silicon alpha detector (RAD-7). Tap water samples were analyzed for radium isotopes (Ra-226 & Ra-228) and measured by gamma spectrometry using high purity germanium detector, after radiochemical separation of the isotopes with ion-exchange chromatography using a strong cation resin. The activity concentrations of 226Ra, 228Ra (232Th series), 137Cs and 40K were determined in the soil samples. Quality assurance and methods validation were established through the efficiency calibration of the detectors, the estimation of uncertainties, the use of blanks, the analysis of standard reference materials and the intercomparison and proficiency tests. The average activity concentrations of 226Ra, 228Ra (232Th series), 137Cs and 40K in soil were 9.3, 9.0, 0.2 and 122.5 Bq/kg respectively, and the corresponding radium equivalent activity had an average of 31.7 Bq/kg, which is far below the value of 370 Bq/kg, as reported in the UNSCEAR. The average absorbed dose rate from outdoor gamma radiation one meter above the ground was 15.4 nGy/hr, which is far below the world average value of 57.0 nGy/hr and the reported values from different regions in KSA. The indoor radon concentrations had an average of 11.8 Bq/m3, which is much lower than the recommended ICRP action level of 200 Bq/m3. The average activity concentrations of 226Ra and 228Ra were 5.3 and 11.0 pCi/L respectively, which is considered in violation of the Saudi Arabian Standards Organization (SASO) authorized limit of 2.7 pCi/L for 228Ra, and the average combined contribution of 226Ra and 228Ra activities to the effective dose from a year's consumption of drinking water in the campus was 0.24 mSv/y, which exceeded the 0.1 mSv/y limit allowed by WHO in drinking water.

Keywords: natural radioactivity monitoring, radium, drinking water, radon, Saudi Arabia.