Effect of Cooking on Arsenic Reduction in Two Rainfed Rice Varieties of Bangladesh and Their Health Risk Assessment

To investigate the effects of cooking on reducing the health risk, the concentrations of total arsenic in raw and cooked rice were measured. Raw rice of two rainfed rice varieties was purchased from market of Dhaka, Bangladesh in 2015. Minikit is a long slender grained popular rice variety in Bangladesh while Kataribhogh is a fine grained aromatic rice which is famous for its aroma and texture. One hundred grams of raw rice was washed with Milli-Q water three times. Then, raw rice was cooked with Milli-Q water: grain ratio of 5:1 in an iron pan covered with lid and the excess water after cooking was decanted. Cooked rice was freeze-dried and ground for arsenic analysis. A microwave digestion was used to digest the rice samples for analysis. Samples were analyzed using inductively coupled plasma mass spectrometer (ICP-MS). The arsenic concentrations in raw rice of Minikit and Kataribhogh in this study were 0.123−0.153 µg g−1 and 0.611−0.783 µg g−1, respectively. On the other hand, the total arsenic contents in cooked rice of Minikit and Kataribhogh were 0.115 ± 0.004 µg g−1 and 0.386 ± 0.004 µg g−1, respectively. There was 17% and 46% reduction of arsenic due to washing and cooking of Minikit and Kataribhogh rice, respectively. Based on the concentration of arsenic in raw and cooked rice, the carcinogenic risk of arsenic via rice ingestion was estimated. The estimated risk of arsenic with cooked rice was 1.2 × 10−5 and 4.1 × 10−5 while that of raw rice was 1.5 × 10−5 and 7.7 × 10−5 for Minikit and Kataribhogh rice, respectively. The results of this study revealed that health risk assessment on the basis of arsenic content of raw rice would be overestimated than the actual health risk.