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Cooking with chloraminated water and salt could create toxic molecules

2 December 2015

Chemical reactions between low level disinfectants in tap water and fortified table salt may be forming toxic chemicals during household cooking processes, according to recent research published in the Water Research journal by environmental scientists in China. Chlorine and chloramines are added to water supplies to prevent microbial contamination and microorganism growth; as much as 4.0 mg/L can be added without causing a chlorine-like taste and odour. Countries identified as having high levels of iodine deficiency within their populations, which can cause stillbirth, miscarriage and thyroid problems, have implemented salt iodization programmes. Potassium iodide and potassium iodate are the most commonly used fortifiers of table salt, at levels between 5-77 mg/kg salt. Common cooking procedures involve boiling these iodinated compounds in tap water containing residual chlorine and chloramines, resulting in the formation of hypoiodous acid, which itself can then react with other organic matter present (either from tap water or from other ingredients in the cooking) to create a number of iodine-containing organic compounds. In recent years, particular attention have been paid to these compounds due to their increased toxicity over chlorine and bromine containing analogues, although some are thought to be more toxic than others. The report also looks at which cooking practices are most likely to reduce the amount of iodine-containing organic compounds generated; reducing cooking temperatures and times, increasing the time interval between additional of ingredients and the addition of iodized salt, and fortifying with potassium iodate, rather than potassium iodide, were all seen to have an effect.

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