Cooking with chloraminated tap water and iodised table salt could put potentially harmful toxins in your food, a new study has warned.

Researchers from the Hong Kong University of Science and Technology and Nanjing University in China found several molecules that are almost completely new to scientists, created by cooking with chloraminated tap water and iodised table salt.

They said that limiting cooking time and temperature, and cooking with table salt fortified with iodate instead of iodide, could be safest.

Our tap water is disinfected before we drink it or use it in cooking. This is done in several ways, including by adding chlorine or molecules called chloramines that are made using ammonia.

These two processes – chlorination and chloramination – have an effect on the chemical make-up of the water.

According to the researchers, chlorine or chloramines in tap water can react with the iodised table salt added to food, creating a kind of acid called hypoiodous acid.

This in itself is not cause for concern, but the acid can then react with the food and other organic matter in the tap water to create cooking iodinated disinfection byproducts (I-DBPs) – molecules that are almost completely new to researchers.

For this study, researchers identified some molecules and tested their toxicity.

“I-DBPs formed during cooking with chloraminated or chlorinated tap water are something new to environmental chemists, toxicologists and engineers,” said Xiangru Zhang, corresponding author of the paper and Associate Professor at the Hong Kong University of Science and Technology.

“They are relevant not only to drinking water researchers and practitioners but also to the public,” he added.

The researchers analysed the I-DBPs formed during cooking with chlorinated and chloraminated tap water.

They simulated cooking with different types of tap water at varying temperatures and time, and added wheat flour and iodised salt to see what I-DBPs would be formed.

Using cutting-edge chemistry techniques, they identified 14 completely new molecules and determined the structure of nine molecules.

They then carried out tests to see how toxic nine of the molecules are and found that some of the molecules are 50-200 times more toxic than others.

The study was published in the journal Water Research.

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