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  1. Salih NF
    Isotopes Environ Health Stud, 2019 Mar;55(1):80-91.
    PMID: 30241441 DOI: 10.1080/10256016.2018.1520708
    This study entails the measurement of the specific activity of natural radionuclides (226Ra, 40K and 232Th) in 18 tooth samples obtained from the clinic of the Universiti Sains Malaysia (USM), Penang, by using an HPGe detector. The specific activity of 226Ra, 40K and 232Th was measured to estimate the hazard index of the radionuclides, radium equivalent activities (Raeq), external, internal hazard indices (Hex, Hin), and absorbed dose (Dout, Din). The maximum values of concentration of 226Ra, 232Th and 40K in the tooth samples were found to be 60.82, 60.29 and 594.22 Bq kg-1, respectively. Maximum values of Raeq, Hex, Hin, Dout and Din were found to be 192.78 Bq kg-1, 0.520, 0.685, 89.29 and 169.81 nGy h-1, Iγ and Iα as 0.702 and 0.304, respectively. The results were lower than the average world value (UNSCEAR). In addition, a strong correlation was found between the concentrations of 226Ra and Raeq, between energy and net area, as well as between radionuclides (226Ra, 40K and 232Th) in tooth samples and age of volunteers. This study showed that the concentrations and hazard indices of tooth samples are below the recommended safe levels; therefore, the study area is considered safe in terms of radiological health hazards.
  2. Salih NF, Jafri ZM, Jaafar MS
    Environ Sci Pollut Res Int, 2016 Dec;23(23):23662-23674.
    PMID: 27619370
    This study was carried out to determine the concentration of (222)Rn, (226)Ra, and (238)U in 25 different toothpastes available in the local market in Penang, Malaysia, using a CR-39 detector. The results showed the maximum concentration of radon/ radium/uranium to be 4197.644 Bq.m(-3), 54.369 Bq.Kgm(-1), and 0.044 ppm in Colgate4; the annual effective dose was found (0.402 mSvy(-1)) in S07. The average concentration of radon (42 %, 3.224 KBq.m(-3)) was higher than the concentration of (214)Po, (218)Po in POS (32 %, 2.415 KBq.m(-3)) and POW (26 %, 1.979 KBq.m(-3)). Also the values of pH of samples ranged from 4.21 (highly acidic) in S04 to 9.97 (highly basic) in S07, with an average of 6.33 which tended towards an acidic behavior; a low or high pH for a long period of time can cause harmful side-effects and enamel erosion. Concentrations of heavy metals varied from the maximum value 56.156 ppm in the Ca elements in the Colgate 4 sample to a minimum value of -0.858 ppm in the Cd elements in Colgate 6 (Ca 56.156 ppm > Cd 51.572 ppm > Zn 41.039 ppm > Mg 11.682 ppm > Pb 11.009 ppm]. Monitoring the accumulation of these metals in toothpaste samples is very important: the average annual effective dose (0.3118 mSvy(-1)) was below the range (3-10 mSvy(-1)) reported by ICRP (1993), and therefore there is no evidence of health problems. Significant strong positive correlations were found (r = 1, Pearson correlation, p 
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