Assessment of natural radioactivity in Moroccan bottled drinking waters using gamma spectrometry

Radioactive elements and their impact on the environment and the food chain, including humans, are a matter of major concern, for which appropriate investigations should be performed. The priority is to examine the concentration of radioactive substances in mineral and bottled spring water. This task aims to analyze the quality of 12 conditioned mineral waters by determining their main radionuclides concentrations, such as ²³⁸U, ²³²Th, and ⁴⁰K. The identification and the quantification of these radionuclides are carried out by their progeny (except the ⁴⁰K) by using a NaI(Tl) detector coupled with a multichannel analyzer (MCA) and connected to a computer. The activity measured in all samples varied from 0.95 to 3.38 mBq.L^-1 with an average of 1.94 mBq.L^-1; from 1.55 to 3.56 mBq.L^-1 with an average of 2.46 mBq.L^-1; and from 200.68 to 269.19 mBq.L^-1 with an average of 236.6 mBq.L^-1, for ²³⁸U, ²³²Th, and ⁴⁰K, respectively. To compare the combined radiological effects of radionuclides present in water, a particular factor Ra(eq) is used. This study showed that the maximum value of Ra(eq) is 27.54 mBq.L^-1, which is far below the activity limit of 370 mBq.year^-1 set by the Organization of Economics and Development (OECD). Concerning the effective annual dose, the following maximums were measured: 1.61 μSv.year^-1, 1.133 μSv.year^-1, and 0.925 μSv.year^-1 for infants, children, and adults, respectively. These values are even smaller than the dose recommended by the WHO which is 100 μSv.year^-1. Regarding the excess lifetime cancer risk index, a maximum of 5.63 × 10^-6 is found. This index value is still less than that proposed by James, namely 2.5 × 10^-3. Thus, the quality of the studied samples respects the radiological international safety and health limits.