ABSTRACT

Activity concentrations were measured in phosphate fertilisers widely used in Saudi Arabia employing gamma ray spectrometry. The activity concentrations of ²³⁸U, ²³²Th and ⁴⁰K were used to estimate the excess lifetime cancer risk (ELCR). The obtained data show that ²³⁸U and ⁴⁰K concentrations are higher than the recommended values (35 Bq kg^–1 and 400 Bq kg^–1 for ²³⁸U and ⁴⁰K, respectively) in most of phosphate fertilisers. The highest value of ²³⁸U was 4122 ± 82 Bq kg^–1 for diammonium phosphate (DAP) fertiliser. Absorbed dose rate, annual effective dose rate and the ELCR were calculated. The results revealed that the values of outdoor, indoor and total ELCR values were higher than the world averages in all samples except one sample, sample of MAP fertiliser (monoammonium phosphate). The highest value of ELCR_tot was for DAP fertiliser which is 50 times higher than the world average value (1.45 × 10^–3). Moreover, the results indicated a strong correlation between uranium in phosphate fertilisers and ELCR_tot. Based on the obtained results, the direct gamma radiation exposure from phosphate fertilisers is a serious radiological threat to the farmers.

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