Study of Naturally Occurring Radioactive Materials and Some Heavy Metals from Intake of Some Nuts and Seeds in South-Western, Nigeria

The concentration of NORMs and some toxic heavy metals in some nuts and seeds commonly consumed in the south-western states of Nigeria were investigated. The analysis was done with NaI(TI) spectrometry and Inductively Coupled Plasma (ICP) respectively. The concentration of 226Ra, 232Th, and 40K in the samples was found to be below the world average. The mean values are 6.6±1.8, 3.6±1.0 and 98.2±13.5 Bq/kg, in nuts and 8.4±2.6, 2.6±1.3 and 97.6±15.0 Bq/kg in seeds respectively. The effective dose in nuts was calculated to be 13.99 and 12.0 µSv in seeds. The fatal and hereditary cancer risk estimated from the consumption of the nuts and seeds are lower than 1.0 x 10-6 which is the lowest limit. Concentration of metals in the samples descend as Fe > Zn > Cu > Cr. The Hazard Indices of heavy metals are lower than 1 except for in Cocoa which is higher than 1 due to the high concentration of Cu and Fe. Therefore, the nuts and seeds analyzed in this study are contaminated with Cu and Fe and so must be taken with care so that consumers will not be exposed to excessive concentration of these metals which may have undesirable effects.