Assessment of naturally occurred radiation hazards in chemical and organic fertilizers used in Chattogram area, Bangladesh

The present work deals with identifying and determining the activity levels of naturally occurring radionuclides Ra-226 and Th-232 series, their decay products and K-40 in chemical and organic fertilisers used in the Chattogram area, Bangladesh. A total of 39 samples collected from retail markets were investigated, out of which 28 are chemical fertilisers and the others are organic fertilisers. The average activity concentration of Ra-226 and Th-232 found in TSP fertiliser are 304.57 +/- 36.0 and 19.1 +/- 6.8 Bq kg(-1) respectively and the average activity concentration of K-40 in MOP fertiliser is found as 10,311.11 +/- 1168 Bq kg(-1). In the organic fertiliser samples, the mean concentration of Ra-226, Th-232 and K-40 are 17.35 +/- 3.1(1), 7.20 +/- 1.74 and 437.14 +/- 42.58 Bq kg(-1), respectively. The mean absorbed dose rates were measured after the end of our experiment, and the value was found to be 91.39 nGy h(-1). The combined (indoor + outdoor) annual effective dose equivalent was also estimated as 0.322 mSv year(-1). The mean radium equivalent activity found to be 190.15 +/- 26.74 Bq kg(-1) is well below the recommended level of 370 Bq kg(1). The internal hazard index, external hazard index, and radioactivity level index of the investigated fertiliser samples were found as 0.56 +/- 0.034, 0.54 +/- 0.08 and 0.69 +/- 0.10, respectively. From the calculated hazard parameters, the excess lifetime cancer risk (ELCR) was found to be higher than the world average in most of the chemical fertilisers except in DAP and BOR, while the organic fertilisers show lower than the world average. The obtained results reveal that there are no significant radiation hazards due to natural radionuclides of the fertiliser samples in the studied area, but the higher concentration of K-40 in MOP suggests strengthening the regulatory work. Overall, this study highly recommends the use of organic fertilisers, as these kinds have hazard parameters lower than the recommended levels.