Indoor and outdoor gamma radiation exposure levels in selected residential buildings across Ondo state, Nigeria

Background: indoor and outdoor gamma radiation exposure levels weremeasured in a total of 360 randomly selected dwellings categorized as local, semimodernand modern buildings across ondo state, nigeria to determine the annualeffective doses. materials and methods: all radiation measurements were takenusing a calibrated kindenoo pg-15 geiger muller detector and a gps forgeographical coordinates of sample points. equal number (360) sample pointmeasurements were carried out for indoor and outdoor measurements.measurements at each location point were performed holding the survey meter at1 m above ground surface or floor to avoid unwanted effects of radiation from soilor building floor. the detector was also held at least six to seven meters away frombuildings nearby in order to avoid unwanted effects of the building materials onoutdoor measurements. each measurement was repeated six times and theaverage was taken to represent the value for a sample point. results: the averageoutdoor and indoor dose rates were determined as 263 ± 32 μsvh-1 and 213± 64 μsvh-1 respectively. the highest contribution to the total indoor dosewas from the local buildings followed by semi modern buildings and themodern buildings contributed the least dose. the average annual effectivedose was calculated as 1.56 ± 0.33 msv, which is higher than the worldaverage value (0.48 msv). conclusion: in view of the potential radiation resultingfrom building materials, comprehensive assessment of natural radiations in suchmaterials is required.