Exposure to Toxic Metals from the Consumption of Rice in Lebanon and the United Arab Emirates

Abstract

Our study aimed to quantify toxic metals (Arsenic, As, Cadmium, Cd, Chromium, Cr, Mercury, Hg and Lead, Pb) in rice, determine the factors affecting its contamination, and evaluate the dietary exposure from its consumption in Lebanon and UAE. A market screening was done and subsequently, all the brands (total of 236 samples, with 107 from Lebanon and 129 from UAE) were collected and tested. Inductively Coupled Plasma-mass Spectrometry (ICP-MS) was used. In Lebanon, the average ± standard deviation in samples was 0.24±0.08, 0.29±0.13, 0.34±0.13, 0.15±0.05, and 0.27±0.10 mg/kg for As, Cd, Cr, Hg and Pb, respectively. In UAE, concentrations were 0.18±0.09, 0.07±0.04, 0.23±0.11, 0.17±0.05, and 0.24±0.08 mg/kg for As, Cd, Cr, Hg and Pb, respectively. In UAE, 9, 1, 100 and 69% of samples exceeded the international limits for As, Cd, Hg and Pb, respectively. In Lebanon, 25, 73, 100 and 69% of samples were above limits for As, Cd, Hg and Pb, respectively. No limits were set for Cr for comparison. In Lebanon, for As, brown rice was significantly more contaminated than white and parboiled rice (p=0.02), long rice grains were significantly more contaminated than short/medium grains (p=0.002), and rice brands originating from developed countries were significantly more contaminated compared to those from developing countries (p<0.001). In UAE, for As, packing season, country of origin, collecting same brands at two different times had significant effect (p= 0.011, 0.016, and <0.001, respectively). In Lebanon, for Cd, collecting same brands at two different times and grain size had significant effect (p<0.001). In UAE, for Cd, collecting same brands at two different times had a significant effect (p=0.008). Regarding Cr, in Lebanon, country of origin, grain size, rice type, and time between packing and purchasing had a significant effect (p=0.006, p<0.001, p<0.001 and p<0.001, respectively). In UAE, for Cr, the only statistically significant variable was collecting same brands at two different times (p<0.001). For Hg in Lebanon, grain size and type had a significant effect (p=0.019 and p=0.012, respectively), while collecting same brands at two different times had a significant (p<0.001) effect in both Lebanon and UAE. None of the variables had a significant effect on Pb in samples from Lebanon. For Pb in UAE, statistical significance was observed for collecting same brands at two different times and country of origin (p=0.004 and 0.001, respectively). Exposure levels to Hg from rice were higher than both FAO/WHO and European Food Safety Authority limits were detected in UAE. In Lebanon, exposure levels were not considered alarming for Cd, Cr and Hg, as the Lebanese rice consumption rate is relatively lower than in UAE, despite the high levels of contamination. No provisional tolerable limits are currently set for As and Pb; thus, the observed exposure to both metals could be a cause of concern in both countries. Future studies must assess the effects of handling and cooking to better assess exposure to toxic from rice exposure in both countries.