Assessment of Natural Radioactivity and Radiological Hazard indices in Cassava Cultivated in Oil Producing Area, Rivers State, Nigeria

Abstract

The natural radioactivity and radiological hazard indices associated with the consumption of cassava crops grown in five communities with history of oil spillage, gas flaring, oil bunkering activities and operation of illegal artisanal oil refining in Rivers State was assessed and measured with gamma ray spectroscopy. Five samples of cassava crop and five samples of soil were collected from the five communities. The results obtained were used to evaluate the soil-to-cassava transfer factor (TF) due to ingestion of cassava crops/staple foods by inhabitants in the area. The mean activity of soil samples ranged from 17.77±4.20Bq/kg to 31.84±3.20Bq/kg for 238U, 22.75±3.30Bq/kg to 33.82±4.70Bq/kg for 232Th and 110.44±9.60Bq/kg to 483.15±18.20Bq/kg for 40K, and is within permissible standard, but is higher than the mean activity in the control. The mean activity of cassava samples ranged from 6.50±1.30Bq/kg to 29.70±6.20Bq/kg for 238U, 5.80±2.20Bq/kg to 16.50±6.80Bq/kg for 232Th and 383.20±28.10Bq/kg to 482.30±35.80Bq/kg for 40K and is found higher than those of the control samples, and the international permissible limits. The study revealed that although some of the radiological hazard indices in the cassava samples were below the allowable standards, the estimated committed annual effective dose and excess lifetime cancer risk due to ingestion of cassava crops/staple foods is respectively over 2.9 times and 5.9 times higher than the international permissible limit of 0.29mSv/y. The rate of radionuclides transferred from soilto-cassava has mean TF of 232Th < 238U