Assessment of Arsenic levels in rice brands sold in Kampala. An experimental study to demonstrate the modifying effect of boiling, soaking and washing

Abstract Background : Arsenic is one of the major toxic metals in the environment that is also known to be carcinogenic with several other health side effects in human beings. It can cause both acute and chronic toxicity depending on the doses available or duration of exposure in the human body. The major sources of arsenic exposure to humans include; via contaminated water, food and inhalation of arsenic dust from polluted air from car-fumes or industrial wastes and mining/ smelting grounds. Due to the fact that high levels of arsenic have been reported in rice from major rice-growing countries in Asia and rice being a major stapple food in Uganda, some of which is imported, this study aimed at determining the concentration of total arsenic in various rice brands sold in Uganda. Methods : Various rice brands weresampled from different supermarkets and grocery shops, taken to the laboratory and analyzed for arsenic using atomic absorption spectrometry. The arsenic concentration in the rice were determined following boiling or overnight soaking in plenty of water to see if these two approaches can help in significantly reducing the arsenic in the rice. The concentration of arsenic in the various brands of rice were compared using an unpaired t-test after setting a p-value of ≤0.05 as significant. Results : The York taste rice brand had the lowest arsenic levels of 1.4±0.0002 ppm and Zhong Yi rice brand had the highest levels of 2.4±0.004 ppm. The tap water used to boil, soak and wash the rice brands had much higher arsenic levels of 3.5±0.000003 ppm, which caused increased retention of the heavy metal in the rice. Conclusion : Rice brands sold in Kampala city seem to have higher than acceptable arsenic levels than what is recommended by WHO or American food and drug authority. The high levels of arsenic in tap water used in preparing the rice causes increased retention of the metal on boiling, soaking and washing. It is therefore, necessary to routinely monitor for arsenic levels in the rice on the market and domestic water sources so as to protect the general public from arsenic toxicity.