Radiological assessment subjected to outdoor radon and thoron concentrations and terrestrial gamma radiation measurements in Perak Malaysia.

The concentrations of radon, thoron and terrestrial gamma radiation were measured to evaluate the outdoor effective dose. The outdoor radon activity concentration ranged from 5.79 to 5110 ± 46.36 Bq m, with a mean of 320.03 Bq m which is higher than the EPA level of 14.8 Bq m. The range of the thoron activity concentration outdoor was from 0.00 to 4226.7 ± 58.5 Bq m, with a mean of 226.1 Bq m which was above the UNSCEAR recommended level of 10 Bq m. The terrestrial gamma radiation dose rates range was from 98.31 to 3769.71 nGy h with a mean of 446.27 nGy h. The effective dose contribution from radon exposures in the study was estimated to be 3.2 ± 0.5 mSv y is about 84% total annual effective dose received by the population in those areas. The estimated thoron and gamma dose contributions (15%, and 1% respectively) were not significant. The outdoor doses for thoron and gamma were lower than the ICRP (2007) value of 1 mSv. The total annual outdoor effective dose with an occupancy factor of 1825 h (5 h day) was estimated to be within the range of 0.30-551.41 ± 0.65 mSv, with a mean of 3.75 mSv which is a little higher than the world average of 2.4 mSv.