Risk Assessment of Gamma Emission from Natural Radioactivity in Soil to Human Body Organs in Oil Palm Processing Mills Environment, Delta State, Nigeria

Abstract

Soil samples collected from communities with palm-oil processing facilities were assessed for activity concentrations of natural radionuclides to ascertain whether the industrial operations have elevated the activity concentrations of the naturally occurring radioactive materials and to examine if the human body organs radiosensitivity to the soil gamma radioactive emissions is within acceptable safety limits set by international regulatory professional bodies. Soil samples collected for the study were measured by gamma ray spectrometry using Thallium activated sodium iodide (NaI[TI]) detector. The mean activity concentration of 238U, 232Th and 40K for the soil samples was respectively 38.35±2.44Bq/kg, 31.00±2.52Bq/kg and 525.37±2.92Bq/kg indicating that 238U and 40K are above the world average reference mean of 33Bq/kg for 238U and 420Bq/kg for 40K. 232Th values were lower than the world average reference mean of 45Bq/kg. Values of absorbed dose rates in soils at Ute-Ogbeje and Mbiri were higher than the permissible safety standard of 59ηGy/h. The mean values of radiological hazard index parameters are all below the international permissible safety standards. The sensitivity of radiation from soil radionuclides to body organs like liver, kidneys, lungs, testes and ovaries were all below the international permissible safety standards of 1.0mSv/y, but the radio-sensitivity showed a decreasing order: Testes > Lungs > Kidneys > ovaries > Liver indicating that testes have the highest radiation sensitivity while the liver have the lowest, therefore no radiological health risk from soil gamma exposure. However, the high values of 238U, 40K, absorbed dose rates and outdoor annual effective dose equivalent for some communities indicates a statistically elevated cancer probability and increased radon potential for the inhabitants. Engineering soil control, groundwater treatment and food safety, and medical surveillance oversight are recommended to address the high outdoor effective dose on community dwellers.