Evaluation of effective dose and excess lifetime cancer risk from indoor and outdoor gamma dose rate of university of Port Harcourt Teaching Hospital, Rivers State
An in-situ measurement of indoor and outdoor radiation dose rate at the University of Port Harcourt Teaching hospital was done using well calibrated radiation meter (Radalert-100). The minimum and maximum indoor gamma dose rate were found to be 121.8 ±4.02 nGyh-1 and 200.1±5.06 nGyh-1 respectively while the minimum and maximum outdoor gamma dose rates were 87.0 ±2.07nGyh-1 and 200.1± 4.07nGyh-1. The study also revealed that the average annual effective dose rate is 0.31±0.002 mSvy-1 and 0.92 ±0.02 mSvy-1for outdoor and indoor measurements respectively. In addition, the excess lifetime cancer risk (ELCR) calculated for indoor exposure ranges from 1.68 × 10-3 to 3.22 × 10-3 with an average value of 0.83 × 10-3. For outdoor exposure ELCR varies from 0.46 × 10-3 to 1.09 × 10-3 with a mean value of 2.289 × 10-3. The average values for indoor and outdoor gamma doses were found to be greater than the world population weighted average for indoor gamma dose rate of 89 nGyh-1. The result shows that ELCR for both indoor and outdoor exposure were higher than the world acceptable value of 0.29 × 10-3,though the annual effective dose levels in all of the locations (indoor and outdoor) were below the 1mSvy-1 maximum permissible limit for the public set by International Commission on Radiological protection (ICRP). Therefore, the management of University of Port Harcourt teaching hospital should undertake a routine maintenance of diagnostic equipment(x-ray machines, CT scanners) may have to avoid leakage which may have contributed to the enhancement of background radiation of the hospital.
Keywords: Dose rate, absorbed dose, background radiation, effective dose, ELCR, radiological