Rice is a potential dietary source of not only arsenic but also other toxic elements like lead and chromium

Abstract

Rice is a staple food and a good source of nutrition for half of the earth’s population including Middle Eastern countries. However, rice may accumulate hazardous levels of toxic elements. In KSA, rice is imported from many countries; some of which suffer from arsenic contamination in their groundwater and soil. Despite the large daily consumption of rice in KSA, no investigations on the contamination of rice sold there are published so far. Additionally, reports on the contamination of rice with other toxic elements are rare in the literature. To investigate this issue, a total of 84 rice samples were collected from local markets in Almadinah Almunawarah, KSA (n = 70) and Brisbane, Australia (n = 12) and analyzed for arsenic and other elements by ICP-MS. The mean concentrations (mg kg−1) for the KSA samples with concentrations >LOQ were 0.136 for As (range 0.026–0.464, n = 70); Cd: 0.017 (0.003–0.046, n = 64); Pb: 0.029 (0.003–0.218, n = 40); Ni: 0.064 (0.042–0.086, n = 5); Mg: 157 (51.8–777, n = 70); Mn: 4.28 (0.960–10.9, n = 70); Fe: 7.07 (1.9–55.1, n = 70); Zn: 6.19 (1.15–13.5, n = 70); Cu 1.28 (0.508–2.41, n = 70); Se 0.202 (0.007–0.574, n = 70); Cr: 0.057 (0.010–0.184, n = 19); and Co: 0.012 (0.001–0.116, n = 56). Several samples were found to contain at least one element in excess of the Chinese MCL (0.2 mg kg−1for Cd, Cr, Pb, and iAs each). A large variation in element concentration was observed for samples of different origins. In comparison, the American rice accumulated the highest arsenic concentration (mean 0.257 mg kg−1) followed by the Thai rice (mean 0.200 mg kg−1), the Pakistani rice (mean 0.147 mg kg−1), the Indian rice (mean 0.103 mg kg−1), and finally the Egyptian rice (mean 0.097 mg kg−1). Additionally, 3 individual samples from Surinam, Australia, and France contained arsenic concentrations (mg kg−1) of 0.290, 0.188, and 0.183. The findings of this investigation indicate that some of the rice varieties sold in KSA contain hazardous levels of arsenic and other toxic elements. For a better public health protection, concerned authorities are highly recommended to regularly monitor the concentrations of not only arsenic, but also other toxic elements (e.g. Cr, Cd, Pb) in rice grains.