Advantages and disadvantages of different pre-cooking and cooking methods in removal of essential and toxic metals from various rice types- human health risk assessment in Tehran households, Iran.

The aim of present study was to evaluate the effects of different pre-cooking and cooking methods on the concentration of toxic (As, Cd and Pb) and essential (Fe, Cu, Co and Zn) metals in widely consumed rice types by Tehran households, Iran. In this regard, a total of 90 samples were obtained from Iranian, Pakistani and Indian rice brands (30 samples from each brand), and were examined in order to determine the concentration of toxic metals including As, Cd, Pb, Fe, Zn, Co and Cu using ICP-OES. Among these rice brands, the most contaminated one was selected in order to evaluate the effects of washing and soaking processes in different time points (1, 5 and 12 h), as well as different cooking methods (Rinsing and Kateh) in reducing the concentration of subjected metals. Nine samples were analyzed for each process, which were 54 samples in total. Our results show that the preparation and cooking methods applied for all rice brands (except for Indian rice) could effectively reduce the non-carcinogenic risk associated with these metals to the acceptable level; however, this is not true about the carcinogenic risk associated with arsenic. Finally, according to our findings it can be concluded that all cooking methods can lead to considerable removal of rice toxic metals (this is partially true about all available rice brands in Iran), however, a large amount of essential metals were also eliminated by these methods. Moreover, after cooking of different rice types in Iran, this food has still carcinogenic risk associated with arsenic.