Heavy metals (As, Cr, Pb, Cd and Ni) concentrations in rice (Oryza sativa) from Iran and associated risk assessment: a systematic review

Rice (Oryza sativa) is the second cereal consumed in Iran. Many studies have been carried out in Iran about the contamination of rice by environmental pollutants such as heavy metals. The aim of present study was: • to systematically review about Arsenic (As), Chromium (Cr), Lead (Pb), Cadmium (Cd) and Nickel (Ni) concentrations in cultivated rice in Iran and; • to estimate the non-carcinogenic risk for age and sex groups. We applied the target hazard quotient (THQ) and total target hazard quotient (TTHQ) to evaluation of the non-carcinogenic risk. International and Iranian databases were searched from January 2008 to October 2016. Data obtained from 27 articles showed that minimum and maximum concentrations of heavy metals were As (0.05 ± 0.09 μg/g dry weight) and Ni (0.83 ± 0.04 μg/g dry weight), respectively. The rank order of heavy metals based on THQ was As > Cr > Pb > Cd > Ni. Also the rank order of consumers rice based on TTHQ were rural females (0.49) > urban females (0.461) > rural males (0.455) > urban males (0.41). Minimum and maximum of TTHQ was related to 35–44 and 15–24 years age groups both males and females, respectively. Since THQ and TTHQ were either lower than 1 value, therefore, consumers were not exposed to carcinogenic risk by consumption of rice cultivated in Iran.