Assessment of the Natural Radioactivity Levels in Soils and the Associated Health Risks to the Public in Mbeya City, Tanzania

Abstract

The objective of this study was to assess the radioactivity levels in soils from Mbeya City and their associated health risks. Samples were collected from selected locations. Then, the samples were analyzed by using an HPGe detector to determine the concentrations of 232Th, 226Ra, and 40K. The concentrations were used to compute the radiation indices. The concentrations ranged from 13.98±1.99 to 275.93±25.88 Bq/kg for 232Th, 5.69±1.48 to 107.49±10.61 Bq/kg for 226Ra and 195.76±21.17 to 1,710.00±161.32 Bq/kg for 40K with an average of 169.55 Bq/kg, 71.86 Bq/kg and 998.42 Bq/kg, respectively. The radium equivalent ranged from 41.10 to 583.93 Bq/kg with an average of 391.19 Bq/kg. The gamma dose rate ranged from 42.97 to 691.85 nGyhr-1 with an average of 467.57 nGyhr-1. The indoor effective dose ranged from 0.21 to 3.39 mSv/y, with an average of 2.29 mSv/y while the outdoor effective dose ranged from 0.05 to 0.85 mSv/y, with an average of 0.57 mSv/y. The internal hazard index ranged from 0.13 to 1.84 Bq/kg with an average of 1.25 Bq/kg while the external hazard index ranged from 0.11 to 1.58 Bq/kg with an average of 1.06.Bq/kg. The results indicate elevated levels of background radiation above the world average and the hazard indices above the ICRP and UNSCEAR recommendations. Therefore, control measures were recommended to protect the public against possible health risks.