Effective Doses and Excess Lifetime Cancer Risks from Absorbed Dose Rates Measured in Facilities of Two Tertiary Institutions in Nigeria

Abstract

This study was aimed at examining the radiation absorbed dose rate, annual effective doses and excess lifetime cancer risks of halls of residence, Radiotherapy Unit and Radiology Department of UI, UCH and UNIMEDTH respectively. Results of measurements show that the mean absorbed dose rate for male and female hall are 0.33 ± 0.05476 and 0.17 ± 0.05074 µSv h-1 respectively. The mean overall absorbed dose rates calculated for facilities studied are 0.269 ± 0.0992 µSv h-1, 0.121 ± 0.036 µSv h-1 and 0.123 ± 0.00931 µSv h-1 in UI, UCH and UNIMEDTH respectively. The mean annual effective doses recorded in both male and female halls in University of Ibadan ranges between 0.71 mSv y-1 and 2.67 mSv y-1. The mean annual effective doses obtained from the facility of University of Medical Sciences Teaching Hospital, Ondo (UNIMEDTH) ranges between 0.17 and 0.44 mSv y-1. In addition, the mean annual effective doses calculated from the measured absorbed dose rate in Radiotherapy Department of University College Hospital, Ibadan ranges between 0.20 and 1.22 mSv y-1. As regards ELCRs, the mean values  determined in various facilities examined are 6.07 x 10-3 (Male Halls, UI), 3.27 x 10-3 (Female Halls, UI), 0.57 x 10-3 (UNIMEDTH- NE), 0.99 x 10-3 (UNIMEDTH- EX), 0.65 x x 10-3 (Teletherapy, UCH) and 0.57 x 10-3 (Brachytherapy, UCH).The mean ELCRs of both halls examined are higher than the world average of 1.45 x 10-3 and the standard value of 0.29 x 10-3 by at least a factor of 1.97 units.